EP4193376A2

EP4193376A2 - Current breaking device for high-dc-voltage electric current, installation comprising such a device, control method and process for evaluating the integrity of an electrical conductor

Info

Publication number: EP4193376A2
Application number: EP21752085.7A
Authority: EP
Inventors: Pascal TORWELLE; Alberto BERTINATO; bertrand Raison; Yang Yang; Wolfgang Grieshaber
Original assignee: Centre National de la Recherche Scientifique CNRS; Institut Polytechnique de Grenoble; Universite Grenoble Alpes; SuperGrid Institute SAS
Current assignee: Centre National de la Recherche Scientifique CNRS; Institut Polytechnique de Grenoble; Universite Grenoble Alpes; SuperGrid Institute SAS
Priority date: 2020-08-05
Filing date: 2021-07-21
Publication date: 2023-06-14
Also published as: FR3113334A1; WO2022029379A3; FR3113334B1; WO2022029379A2

Abstract

The invention relates to a breaking device (28) for a high-DC-voltage current including, in succession, an isolating switch (48), a first primary point (44.1) and a first breaking module (40.1), characterized in that the breaking device (28) includes, between the first primary point (44.1) and ground (52), a precharge circuit (50) that has a precharge capacitor (54, 54.1), a precharge resistor (56) and a precharge switch (58), and in that the breaking device has at least: - one charging configuration (C_CH) for allowing the precharge capacitor to be charged; and - one precharging configuration (C_PCH) for allowing the precharge capacitor (54, 54.1) to be discharged into a conductor (12). The invention also relates to a method for controlling such a device and a process for evaluating the integrity of an electrical conductor.

Description

Title of the invention: Current cut-off device for electrical current under high direct voltage, installation with such a device, control method, and process for evaluating the integrity of an electrical conductor

Technical area

[0001] The invention relates to the field of high voltage direct current (HVDC) electrical current cut-off devices and their control methods. Such devices are intended to be implemented in HVDC network units in the event of the appearance of an electrical fault in an electrical conductor of this network unit.

[0002] HVDC network units are in particular envisaged as a solution for the interconnection of disparate or non-synchronous electricity production sites, in particular to increase the capacity for transporting energy between countries (interconnections between countries), via so-called energy highways. HVDC network units are particularly considered for the transmission and distribution of energy produced by wind farms rather than alternating current technologies, due to lower line losses and no incidence of parasitic capacitances in the network unit over long distances. Such HVDC network units typically have voltage levels in the order of 100 kV and above.

[0003] In the present text, for a device in which a current under continuous high voltage flows, the high voltage device is considered to be either a "high voltage A" device, in which the nominal operating voltage is continuous and greater than 1500 V, but less than or equal to 75,000 V (75kV), i.e. a "high voltage B" device when the rated service voltage is continuous and greater than 75,000 V (75kV). Thus, the DC high voltage domain includes the “high voltage A” domain and the “high voltage B” domain. [0004] Breaking off the DC high voltage current in such networks or network units is a crucial issue directly conditioning the feasibility and development of such networks.

Generally, in the field of high voltages, direct or alternating, at each of the two ends of an electrical conductor, there is an electrical cut-off device capable of cutting off the flow of electrical current in the conductor, whether the current is the rated current, which is the maximum current that the conductor is likely to conduct in steady state, or a fault current, which may exceed this rated current. In the event of a fault, the electrical network is designed to implement a network fault elimination strategy, aimed at interrupting the current in the faulty electrical conductor. Breaking electrical currents under high direct voltage (HVDC) is more complex to achieve than breaking currents under alternating voltage (AC). Indeed, when breaking an alternating current, we take advantage of a passage through zero of the current to carry out the electrical break, which we cannot benefit from with a current under direct voltage, in particular HVDC. In the event of a fault, the electrical network is designed to implement a network fault elimination strategy, aimed at interrupting the current in the faulty electrical conductor.

Prior technique

[0006] Most of the currently planned HVDC network units will use buried or submarine cables as electrical conductors, since the right of way for overhead conductors is difficult to obtain. However, the overhead conductors of the existing overhead lines, intended for the circulation of alternating currents, could be upgraded and subsequently used in the HVDC network units as electrical conductors, which would be an attractive solution due to the both its simplicity and its cost-effectiveness.

Each of these two types of electrical conductors may, in service, experience electrical faults.

[0008] The probability of a fault occurring is higher for overhead conductors, in particular due to their exposure to weather conditions. difficult, such as lightning strikes. Indeed, a lightning strike on an overhead conductor produces overvoltages which can temporarily affect the dielectric properties of the insulators and lead to a breakdown of the insulation. This therefore necessarily leads to having to isolate the conductor in which the fault has appeared by opening an electrical cut-off device with respect to the rest of the network. Generally, a given conductor is provided, at each of its two ends, with a breaking device, and in the event of the appearance of a fault, the two breaking devices are open to isolate the conductor, and therefore isolate the fault. compared to the rest of the HVDC network unit. After the insulation of the conductor thus impacted and after the deionization of the air, the conductor could be reconnected to the HVDC network unit since the fault generated by a lightning strike is very often non-persistent. This process is called automatic re-closing, by closing the breaking device(s) which have been opened to isolate the conductor. However, other fault scenarios could cause permanent insulation failure. In this case, automatic re-closing would lead to a second fault on the conductor in question and would require the reopening of the breaking device(s) which makes it possible to isolate this conductor. In general, the electrical network operator sets a maximum number of successive re-closure attempts that can be attempted following the isolation of a faulty conductor. These successive re-closing attempts are conducted in a short period of time to minimize the time during which the driver is unavailable. Of course, successive attempts at re-closing on a conductor which has a permanent fault are doomed to failure, and this succession of attempts leads to a certain number of problems concerning the stability of the network and increases the stresses on the component. breaks, such as:

- disturbances in the HVDC network unit;

- an interruption or disturbance of power flow which may lead to instability of any network units under alternating voltage connected to this network unit;

- high requirements for high energy absorption in a short time, for example in lightning arresters; - A significant thermal impact on the components of any adjacent electrical power converters, in particular on the freewheel diodes of such converters.

[0009] The aforementioned problems are the consequence of the fact that before automatic reclosure, the driver's state of health is unknown. Therefore, the main problem to be solved is the evaluation of the persistence of the fault on the conductor. Research has shown that recurrence of the fault is more likely at voltage levels close to the nominal voltage. Thus, a fault may not manifest at low voltage levels (see for example G. Ebner, W. Hartmann, M. Hergt and S. Wietzel, "Fault arc extinction and system re-start on HVDC transmission lines using LCC or VSC full-bridge converters with integrated arc recovery simulation models," 13th IET International Conference on AC and DC Power Transmission (ACDC 2017), Manchester, 2017, pp. 1 -5, doi: 10.1049/cp.2017.0018). This implies that a reliable evaluation is only possible when the conductor is fully charged, i.e. when its electrical potential is brought to a potential which represents a significant proportion of its electrical potential in nominal operation.

It has already been proposed to have, in series with the conductor, an insertion resistor device consisting of a resistor in parallel with a short-circuit switch. There are solutions in which the insertion resistor device is integrated into the breaking device (see for example J. Shu, S. Wang, T. Liu, , “A Soft Peclosing Model for Hybrid DC Circuit Breaker in VSC -MTDC System,” 2018 IEEE 4th South. Power Electron. Conf., pp. 1-5, 2018). In normal operation, the resistor is bypassed keeping the shorting switch in its closed state. After the faulty line is isolated by the breaking device, the short-circuit switch in parallel with the resistor goes into the open state. When re-closing the breaking device, an initial inrush current is observed due to the potential difference between the HVDC network unit and the conductor which was previously insulated and discharged through the fault. In the event of a non-permanent fault, the presence of the insertion resistor in series with the conductor makes it possible to limit the inrush current and therefore to limit the disturbances in the HVDC network unit. Also, the insertion resistor limits the surge in the conductor, when the incoming voltage wave is reflected at twice its rated value, considering an open circuit at the other end of the conductor. In the case of automatic re-closing on a persistent fault, the insertion resistor can also limit the fault current and therefore the voltage on the breaking device. However, even if the impact of automatic re-closing on a persistent fault is lower with an insertion resistor, there is still a disturbance on the DC network side, and component wear. Also, no prediction is made before the start of the automatic re-closing process.

[0011] In the document Vinothkumar, K., Segerqvist, I., Johannesson, N., & Hassanpoor, A., (2016), “Sequential auto-reclosing method for hybrid HVDC breaker in VSC HVDC links”, “2016 IEEE 2nd Annual Southern Power Electronics Conference (SPEC)”, 1-6, the proposed solution is based on a hybrid-type DCCB with multiple sub-modules connected in series. The hybrid type DCCB is composed of a main branch, a main breaking branch and an energy absorbing branch. The main branch contains a high-speed disconnector (UFD) and a load switching switch (LCS) in series. The main cutoff branch contains a stack of IGBT modules. Parallel to each stack, a surge suppressor (SA) absorbs energy during the opening sequence. Once the faulty overhead conductor has been isolated and the de-ionization time (200ms-500ms) has elapsed, the proposed automatic re-closing sequence proceeds as follows:

- 1 . Sequential closing of the breaking modules to gradually increase the voltage on the overhead conductor side;

- 2. Verification of the persistence of the fault using a fault detection algorithm;

- 3. If the fault persists, all the breaking modules open again.

[0012] This process is repeated until the maximum number of attempts, defined by the network operator, is reached. To avoid unacceptable thermal heating of surge arresters (SA), the document proposes to alternate the choice of breaking modules to be closed. However, this solution requires an ultra-fast circuit breaker, therefore of the hybrid type, due to the rapid operation time in the event of a persistent fault. Additionally, surge arresters (SA) must be designed for such energy absorption. The proposed solution still risks causing complete re-closure on a fault that is still present because no evaluation of the health of the overhead conductor is made before complete re-closure, which here also leads to wear of the components.

The document WO2018162421 describes a method for closing a circuit breaker (10) having a main branch (M), which comprises a main module comprising a sub-branch comprising a mechanical switch-disconnector (UFS) connected to two circuit breaker consisting of a power semiconductor element with controlled duty cycle, the main branch (M) being connected to a pre-insertion module. The circuit breaker (10) and the pre-insertion module form an assembly having a first (111) and a second (112) terminal, respectively connected to a source (S) and to the power transmission link (C). In parallel with the main branch, there is a parallel arm (Arm) comprising two thyristors in opposite directions and a capacitor in parallel with both a resistor and a switch. Finally, also in parallel with the main branch, there is an energy absorption branch (Ex) which is here made in the form of a surge protector (SA3).

The method comprises the steps of: a) first closing the mechanical switch-disconnector (UFS) when the voltage difference between the voltages at the first and second terminals is lower than a predefined voltage; b) closing the bypass switch (S2); and c) closing the power semiconductor element.

During the opening sequence, the fault current is redirected from the main branch to the parallel arm by turning on the thyristor in the parallel arm and then opening the mechanical switch-disconnector (UFS). This is possible, since the capacity was initially discharged. When charged to the protection voltage level of the switch-disconnector mechanism (UFS), the magnetic energy is absorbed, which forces a zero crossing of the fault current. Before starting the re-closing sequence, the capacitor must be discharged by the resistor in parallel. The reclosing sequence begins with the thyristor in the parallel arm branch closing, resulting in a current that charges both the capacitor and the transmission line. In the event of a persistent fault, the capacitor continues to charge up to the protection voltage level of the surge protector and the rest of the energy is absorbed by the SA3 surge protector. The advantage of this solution is that the mechanical switch-disconnector (UFS) does not need to be opened again since the current passes directly through the parallel arm. However, in the event of a persistent fault, the initial current remains high since the reopening takes place on a discharged capacitor without any resistance. Also, the condition of the transmission line is not evaluated before re-opening.

[0016] The document S. Zhang, G. Zou, B. Li, B. Xu, and J. Li, “Electrical Power and Energy Systems Fault property identification method and application for MTDC grids with hybrid DC circuit breaker ¹ ', “ Electr. Power Energy Syst.”, vol. 110, no. January, pp. 136-143, 2019, further describes a solution implementing a hybrid breaking device. The proposed device comprises an auxiliary circuit for a hybrid breaking device. The main circuit consists of several sub-modules in series. Each sub-module is composed of an IGBT module in parallel with a snubber circuit, which basically consists of a small capacitance and a small resistor in parallel with a diode. The idea is to interconnect the sub-modules in such a way that the capacitance is used to send trigger signals (10 to 20% of the nominal voltage) in the line. In a later step, the persistence of the fault is identified using a “wavelet transform” algorithm which analyzes the reflected traveling waves created either by the fault or by the open circuit at the far end of the line. The auxiliary circuit includes at least one thyristor between each sub-module, a grounding resistor Rg and a fast grounding switch (FMS). The proposed solution aims to evaluate the fault condition of the transmission line before re-closure. However, several problems remain. The solution sends low amplitude trigger signals which do not provide reliable information because the fault may reappear after complete re-closure, once the line again reaches a voltage close to the nominal voltage. The intent is clearly to analyze the trigger signal and not to energize the line, so there will still be a large current when fully re-closing on the unloaded transmission line. Furthermore, the proposed solution is strongly limited to the specific architecture of the hybrid breaking device which is described.

[0017] The document WO-2014/166528 describes a device which comprises a capacitor 104 which is in a branch between the ground and an intermediate point of the main line, this intermediate point being arranged between a cut-off switch 102 and a switch of insulation 126. This capacitor 104 has only the role of storing energy in order to create a current oscillation through the cut-off switch 102 to cut an electric arc when it opens. The branch in which this capacitor 104 is located is intended to be part of an oscillation loop 103 when the switch 106 is closed, an oscillation loop whose purpose is to generate the current oscillation capable of extinguishing the arc in cut-off switch 102. This document is primarily concerned with the opening of cut-off switch 102.

The document EP-3.089.301 describes a device making it possible to inject a countercurrent through the cut-off switch 110 regardless of the direction of circulation of the fault current. This document is also concerned with the opening of cut-off switch 110.

[0019] The object of the invention is therefore to propose a device and a method which make it possible to secure the re-closing sequence of a switching device which has been previously opened to isolate a conductor from an electrical line arranged downstream of this cut-off device, in particular in the case of an overhead conductor of an overhead electrical power transmission line.

Disclosure of Invention

[0020] For this purpose, the invention proposes a cut-off device for electrical current under high direct voltage comprising:

- a main circuit, in which a nominal direct current flows in a conduction configuration of the cut-off device, the main circuit extending between an upstream point intended to be electrically connected to a DC high voltage source and a downstream point intended to be electrically connected to a conductor of a downstream electrical line ;

- at least one first cut-off module comprising at least one cut-off switch interposed in the main circuit between a first primary point and a first secondary point of the main circuit, the first primary point and the first secondary point being located in this order in the main circuit between the upstream point and the downstream point, and the cut-off switch being capable of being controlled between an open state and a closed state to respectively determine an open state and a closed state of the first cut-off module;

- an isolation switch, interposed in the main circuit between the upstream point and the first primary point, the isolation switch being capable of being controlled between an open state and a closed state.

The cut-off device comprises a pre-charge circuit which extends between the first primary point and the ground (52) and which comprises at least one pre-charge capacitor, at least one pre-charge resistor and a preload switch.

[0022] The cut-off device has at least:

- a charging configuration in which the precharging switch is in a closed state such that the precharging capacitor, the precharging resistor and the precharging switch are all electrically in series in the charging circuit pre-charge between the first primary point and the ground, while the first primary point is electrically isolated from the downstream point of the cut-off device but electrically connected to the upstream point to allow charging of the pre-charge capacitor;

- a pre-charge configuration in which the pre-charge switch is in its closed state such that the pre-charge capacitor, the pre-charge resistor and the pre-charge switch are all electrically in series in the pre-charging circuit between the first primary point and the earth, while the first primary point is electrically isolated from the upstream point of the breaking device but electrically connected to the downstream point to allow a discharging the pre-charge capacitor into the conductor of the downstream power line;

- an isolation configuration in which the first primary point is isolated from the upstream point, with the isolation switch in its open state, and is isolated from the downstream point, with the cut-off switch in its open state.

[0023] In the conduction configuration, the pre-charge switch is open to isolate the first primary point from ground, and the upstream point is electrically connected to the downstream point by the main circuit comprising the cut-off switch and the isolation switch both in their closed state.

The invention also provides such a device with the following optional characteristics, taken individually or in combination.

[0025] The first cut-off module may comprise a cut-off assistance circuit which extends electrically by-passing the cut-off switch and the main circuit between the first primary point and the first secondary point of the main circuit, and, in a cut-off configuration, the cut-off device can then be configured such that at least one pre-charge capacitor of the pre-charge circuit forms part of the cut-off assistance circuit of the first cut-off module.

[0026] The cut-off device may comprise, downstream of the first cut-off module in the main circuit of the cut-off device, at least one last cut-off module comprising at least one cut-off switch interposed in the main circuit between a last primary point , downstream of the first secondary point, and a last secondary point of the main circuit, and the cut-off switch of the last cut-off module being able to be controlled between an open state and a closed state to respectively determine an open state and a closed state of the last breaking module.

[0027] The last cut-off module may include a cut-off assistance circuit which extends electrically by-passing the cut-off switch of the last cut-off module and of the main circuit, between the last primary point and the last point secondary of the main circuit, and, in a breaking configuration, the breaking device can be configured such that at least a pre-charging capacitor of the pre-charging circuit is part of the cut-off assistance circuit of the last cut-off module.

[0028] The pre-charge circuit may comprise at least one first pre-charge capacitor and at least one second pre-charge capacitor, and, in the cut-off configuration, the cut-off device may be configured such that the first pre-charge capacitor forms part of the cut-off assistance circuit of the first cut-off module while the second pre-charge capacitor forms part of the cut-off assistance circuit of the last cut-off module.

[0029] The cut-off device may comprise, in the main circuit of the cut-off device, between the first cut-off module and the last cut-off module, at least one additional cut-off module comprising at least one cut-off switch interposed in the circuit main between an additional primary point, downstream of the first secondary point, and an additional secondary point of the main circuit, upstream of the last primary point, and the cut-off switch of the additional cut-off module being able to be controlled between a state open and a closed state to respectively determine an open state and a closed state of the additional breaking module.

[0030] An additional cut-off module may comprise a cut-off assistance circuit which extends electrically by-passing the cut-off switch of the additional cut-off module considered and of the main circuit between the additional primary and secondary points of the circuit which correspond to the additional cut-off module considered, and, in a cut-off configuration, the cut-off device can be configured such that at least one pre-charge capacitor of the pre-charge circuit forms part of the assistance circuit to the breaking of the additional breaking module.

[0031] The cut-off device may comprise a single cut-off module, the cut-off assistance circuit of which comprises, successively and in this order from the first primary point, the at least one pre-charge capacitor and a circuit breaker. activation, with a tapping point between the two in the cut-off assistance circuit, the pre-charge circuit may comprise a first section, which is common with the cut-off assistance circuit, which extends between the first primary point and the tapping point and which comprises the at least one pre-charge capacitor, and the pre-charge circuit comprises a second section, distinct from the cut-off assistance circuit, which extends between the tapping point and the earth and in which the pre-charge switch is interposed.

The cut-off device may comprise at least one upstream cut-off module and a downstream cut-off module whose cut-off assistance circuits are, in the cut-off configuration of the cut-off device, arranged electrically in series; the cut-off assistance circuit of the downstream cut-off module may comprise, successively and in this order from the downstream primary point, the at least one pre-charge capacitor and an activation switch, with a tapping point between both in the cut-off assistance circuit, and the pre-charge circuit may comprise a first section which extends between the upstream primary point and the tapping point, which is common with the cut-off assistance circuits series cut-off, and which comprises the at least one pre-charge capacitor of each of the series cut-off assistance circuits, and the pre-charge circuit may comprise a second section, separate from the the break, which extends between the tapping point and the earth and in which the pre-charge switch is interposed.

[0033] The current cut-off device may comprise a bypass circuit which extends, electrically in parallel with the main circuit, between the first primary point and a bypass point arranged between the last secondary point and the point downstream, and in which is interposed a bypass switch which is in a closed state in the pre-charge configuration and in an open state in the charging, isolation and cut-off configurations.

[0034] The cut-off device may comprise a configuration switch which is arranged in the main circuit between the last secondary point and the bypass point, and which is in an open state in the pre-charging and charging configurations. , and in a closed state in the conduction and cut-off configurations.

[0035] The breaking device may comprise at least one shunt switch which, in the charging configuration and in the pre-charging configuration, is in a closed state to connect in series, in the pre-charge circuit, the pre-charge capacitors belonging to the various cut-off modules.

The cut-off switch of a cut-off module may comprise a primary, mechanical switch, and a secondary, mechanical switch, interposed successively in the main circuit between the primary point and the secondary point which correspond to the cut-off module considered. , but on either side of an intermediate point of the main circuit which corresponds to the cut-off module considered, the two mechanical switches each being controlled between an open state and a closed state, and this cut-off module may comprise a primary surge protector arranged in parallel with the primary switch between the primary point and the intermediate point which correspond to the breaking module considered, and a secondary surge protector arranged electrically in parallel with the secondary switch between the intermediate point and the secondary point which correspond to the switching module cut considered, and the cut assistance circuit of this cut module considered little t extend electrically in parallel with the assembly formed by the primary switch and the secondary switch of this switching module considered, and electrically in parallel with the assembly formed by the primary surge arrester and the secondary surge arrester of this switching module cut considered.

The downstream power line may comprise an overhead line, the conductor of the downstream power line being an overhead conductor.

The invention also relates to an electrical installation comprising a DC high voltage source electrically connected to at least one aerial conductor of a downstream electric line comprising an aerial line, characterized in that it comprises, interposed between the source of high voltage direct current and the aerial conductor of the downstream electrical line comprising an overhead line, a current breaking device having any one of the preceding characteristics, the high voltage direct current source being connected to the upstream point of the breaking device, and the aerial conductor being electrically connected by an upstream end to the downstream point of the cut-off device. Such an electrical installation may comprise, at a downstream end of the conductor of the downstream electrical line, another power cut-off device.

[0040] The invention also relates to a method for controlling the closing of such a current cut-off device, the cut-off device being initially in the isolation configuration, characterized in that the control method comprises at least one step pre-charging of the conductor during which the switching device is brought into its pre-charging configuration to energize a conductor of a downstream electric line downstream of the downstream point (38), and in that the method closing control comprises, during or after the conductor pre-charging step, at least one parameter determination step) comprising the determination of at least one current or voltage parameter in the main circuit or in the line electrical outlet, and a decision step, during which it is decided, depending on the at least one parameter determined during the parameter determination step, whether or not to continue the complete closing of the device switching off by switching from the current switching device to the conduction configuration.

The invention also proposes such a control method with the following optional characteristics, taken individually or in combination.

[0042] Thus, in such a method, it is possible to provide that, to reach the conduction configuration, the pre-charge switch is open before the closing of the cut-off switch and the isolation switch.

In such a method, if the decision step is not positive, provision can be made for the method to continue, without going through the conduction configuration of the cut-off device, by a step of recharging the capacitor of pre -charging during which the breaking device is brought into the charging configuration, then successively by a new driver pre-charging step, a new parameter determination step, and a new decision step, according to a cycle of pre-charge.

The pre-charge capacitor recharging step can include:

- the closing of the isolation switch and the closing of the pre-charge switch for charging the pre-charge capacitor, maintaining the cut-off switch in its open state;

- after said closing of the pre-charge switch, the reopening of the isolation switch.

[0045] The number of pre-charge cycles for a given reclosing attempt of the breaking device can be limited.

[0046] After at least one conductor pre-charging step, the complete closing of the current breaking device by passing the breaking device to its conduction configuration can be continued if a voltage value in the main circuit, or in the downstream power line, exceeds a threshold value.

[0047] The invention also proposes a process for evaluating the integrity of an electrical conductor in an electrical power transmission line in an electrical installation comprising a main source of continuous high voltage electrically connected to an upstream end of the conductor. electrical, with an upstream current cut-off device interposed between the main voltage source and with a downstream end of the electrical conductor connected to a downstream electrical cut-off device, the evaluation process being of the type in which, in an initial state, the upstream breaking device and the downstream breaking device are respectively each in an isolation configuration so that, in the initial state, the electrical conductor is, except for an electrical fault affecting the electrical conductor, electrically isolated from the installation and of the environment, characterized in that the evaluation process comprises at least one step of pre-charging the condition uctor in which an auxiliary voltage source, distinct from the main voltage source, is connected to the conductor to energize the electrical conductor while maintaining the conductor insulated from the main voltage source and from the rest of the electrical installation. Such an evaluation process comprises, during or after the conductor pre-charging step, at least one parameter determination step comprising the determination of at least one current or voltage parameter in the downstream electrical line, and a step evaluation during which the integrity of the electrical conductor is evaluated according to the at least one parameter determined during the step of determining the parameter.

Such an evaluation process may comprise or be followed by a decision step, during which it is decided, depending on the at least one parameter determined during the parameter determination step, of the continuation or not of the complete closing of the current breaking device by switching the current breaking device to a conduction configuration.

Brief description of the drawings

[0049] [Fig. 1] Figure 1 is a general schematic view of an electric current transmission and distribution installation comprising a multi-terminal HVDC current network unit in which a device and a method according to the invention can be implemented.

[0050] [Fig. 2] Figure 2 shows a point-to-point HVDC current network unit in which a device and a method according to the invention can be implemented.

[0051] [Fig. 3] Figure 3 shows a slightly more detailed view, while remaining schematic and simplified, of part of the installation 10, illustrating the environment of a cut-off device of an HVDC network unit in accordance with the teachings of the invention.

[0052] [Fig. 4A-4B] Figures 4A and 4B are simplified diagrams of the part of the installation 10 which is illustrated in FIG. 3, illustrating the disconnect device isolation configuration and a preparation configuration.

[0053] [Fig. 5A-5B] Figures 5A and 5B are simplified diagrams of the part of the installation 10 which is illustrated in FIG. 3, illustrating a control sequence of the breaking device including its transition from a preparation configuration to its pre-charge configuration.

[0054] [Fig. 6A-6D] Figures 6A to 6D are simplified diagrams of the part of the installation 10 which is illustrated in FIG. 3, illustrating a piloting sequence of the switching device comprising its passage through a charging configuration of the pre-charging capacitor.

[0055] [Fig. 7A-7C] Figures 7A-7C are simplified diagrams of the part of the installation 10 which is illustrated in FIG. 3, illustrating a control sequence of the switching device including its transition to a conduction configuration.

[0056] [Fig. 8] FIG. 8 is a schematic flowchart of an electrical protection method comprising a method for controlling the closing of a cut-off device 28 according to the invention.

[0057] [Fig. 9A] Figure 9A illustrates another embodiment of a switching device according to the invention.

[0058] [Fig. 9B] FIG. 9B is a table indicating the switching states of the various switches of the FIG. 9A, in different configurations of this cut-off device.

[0059] [Fig. 10A] Figure 10A illustrates another embodiment of a switching device according to the invention.

[0060] [Fig. 10B] Figure 10B is a table similar to that of FIG. 9B for the cut-off device of FIG. 10A.

[0061] [Fig. 11 A] Figure 11 A illustrates another embodiment of a switching device according to the invention.

[0062] [Fig. 11B] FIG. 11B illustrates a variant of the switching device of FIG. 11 A according to the invention.

[0063] [Fig. 11C] Figure 11C is a table similar to that of FIG. 9B for the breaking devices of Figs. 11A and 11B.

[0064] [Fig. 12A] Figure 12A illustrates another embodiment of a switching device according to the invention.

[0065] [Fig. 12B] Figure 12B is a table similar to that of FIG. 9B for the cut-off device of FIG. 12A

[0066] [Fig. 13A] FIG. 13A illustrates another embodiment of a switching device according to the invention. [0067] [Fig. 13B] Figure 13B is a table similar to that of FIG. 9B for the cut-off device of FIG. 13A.

[0068] [Fig. 14A] Figure 14A illustrates another embodiment of a switching device according to the invention.

[0069] [Fig. 14B] Figure 14B is a table similar to that of FIG. 9B for the cut-off device of FIG. 14A.

[0070] [Fig. 15A] Figure 15A illustrates another embodiment of a switching device according to the invention.

[0071] [Fig. 15B] Figure 15B is a table similar to that of FIG. 9B for the cut-off device of FIG. 15A.

[0072] [Fig. 16A] Figure 16A illustrates another embodiment of a switching device according to the invention.

[0073] [Fig. 16B] Figure 16B is a table similar to that of FIG. 9B for the cut-off device of FIG. 16A.

[0074] [Fig. 17A] Figure 17A illustrates another embodiment of a switching device according to the invention.

[0075] [Fig. 17B] Figure 17B is a table similar to that of FIG. 9B for the cut-off device of FIG. 17A.

Description of embodiments

[0076] FIG. 1 shows an example of an electrical current transmission and distribution installation 10 comprising a high voltage direct current electrical current network unit, hereinafter referred to as the HVDC network unit 12. The HVDC network unit 12 operates under a single rated working voltage which is a continuous high voltage, for example with a continuous rated working voltage greater than 75,000 V (75kV).

In an electric network, the transmission of electric power between two given points of the network is done by a power transmission line which generally comprises several conductors, each of which corresponds to an electric pole of the power transmission line. In any case, at meaning of this text, an electrical conductor can be in the form of a single electrical conductor which extends between two distinct points of a network unit considered, or in the form of a set of electrical conductors which extend in parallel electrically between two distinct points of a considered network unit, all the conductors of the assembly being, at all times, at the same electric potential for the same position between the two distinct points along each of these conductors (this in order to take into account a possible voltage drop along each given conductor due to the resistivity of the conductor).

Thus, in an HVDC network unit, the transmission of electrical power between two given points of the network is done by a power transmission line which, in many cases, comprises two electrical poles, each pole comprising an electrical conductor which extends between the two given points of the network. In this case, the power transmission line therefore comprises two electrical conductors of different polarities, with, under load, for example an electrical conductor which is at a positive potential and an electrical conductor which is at a negative or neutral potential. Still in an HVDC network unit, the transmission of electrical power between two given points of the network can also be done by a power transmission path with three electrical poles comprising three electrical conductors, with, under load, an electrical conductor which is at a positive potential, an electrical conductor that is at a negative potential, and an electrical conductor that is at a neutral potential. In some cases, the transmission of electrical power between two given points of the network can be done by a power transmission line with a single electrical pole, with an electrical conductor at line potential and with an electrical return through earth.

[0079] In Figs. 1 and 2, a single line represents a power transmission line between two distinct points of a network unit, in particular in the HVDC network unit 12, in order to clearly show the topology of the network without having to go into technical details. Similarly, where an electric bus has been represented at a given point of the network unit, there will in reality be as many electric buses as the number of poles, therefore as many electrical buses as the number of electrical conductors in the transmission lines starting from the point considered. For example, it can be assumed that only the electrical conductors and the electrical buses corresponding to a positive pole have been represented in the HVDC network unit 12.

[0080] In the example of FIG. 1, the HVDC network unit 12 has 4 terminals, in this case a first terminal 14.1, a second terminal 14.2, a third terminal 14.3 and a fourth terminal 14.4. The HVDC network unit 12 comprises, to electrically connect these 4 terminals, electrical conductors 21, 22, 23, 24, electrical buses 26.1, 26.2, 26.3, 26.4, cut-off devices, etc. which all operate under the rated working voltage of the HVDC 12 network unit.

[0081] FIG. 2 shows another example of an electrical current transmission and distribution installation 10 comprising an HVDC network unit 12. In this second example, the HVDC network unit 12 has 2 terminals, in this case a first terminal 14.1 and a second pair of terminals 14.2. The HVDC network unit 12 comprises, to electrically connect these 2 terminals, a single electrical line comprising an electrical conductor 21 which extends electrically between two electrical power converters 18.1, 18.2, with interposition, at each end of the electrical conductor 21 , switching devices 28.1, 28.2 which operate under the nominal service voltage of the HVDC network unit 12.

At each of its 4 terminals, the HVDC network unit 12 of FIG. 1, is connected to another network unit 16.1, 16.2, 16.3, 16.4. In the example, each of these other network units 16.1, 16.2, 16.3, 16.4 is an alternating voltage network unit, so that each of the 4 terminals 14.1, 14.2, 14.3 and 14.4 is actually connected to the DC side of an AC-DC power converter 18.1, 18.2, 18.3, 18.4. However, one or the other or several of these other network units 16.1, 16.2, 16.3, 16.4, could be of another nature, and could for example be another HVDC network unit. Each of these other network units 16.1, 16.2, 16.3, 16.4 can be an electricity production network unit (for example a wind farm), and/or an electricity transmission and distribution network unit . [0083] In the example illustrated in FIG. 1, the HVDC network unit 12 comprises several link nodes, in this case 3 link nodes, here made in the form of electrical buses 26.1, 26.3 and 26.4, each of which comprises at least three separate links which are electrically connected between them in a continuous manner, that is to say without the possibility of an electrical cut between the links.

[0084] The link node 26.1 illustrated in FIG. 1 is made in the form of an electrical bus and comprises a first connection 26.11 which is electrically connected to a proximal end of a first electrical conductor 21 of a first power transmission line of the electrical network unit considered, with the interposition of a first electrical cut-off device 28.11, associated with the first link 26.11, which has an open state and a closed state. In its closed state, the first electrical cut-off device 28.11 allows the circulation of a first power flow between the connection node considered and the first conductor 21, in the first connection 26.11. This first power flow corresponds, in normal service and in the absence of a fault, to that which circulates in the first conductor 21. In its open state, the first electrical cut-off device 28.11 interrupts the circulation of all electrical power between the node link considered and the first conductor 21, in the first link 26.11.

[0085] In general, an electrical cut-off device may comprise one or more current cut-off devices, in particular of the switch type, arranged in parallel and/or in series between an input point of the device and an output point of the device. In the open state, an electrical cut-off device prevents the flow of current through the device. In a closed state, an electrical cut-off device allows an electrical current to flow through the device. An electrical cut-off device may comprise one or more circuit breaker type devices, optimized to interrupt an established current, and/or one or more disconnector type devices, optimized to maintain electrical insulation between its two terminals when it is in a state open. Such devices can be mechanical, electronic or hybrid devices. However, in the example, the first device of electrical cutoff 28.11 is preferably of the mechanical type, in which the electrical cutoff corresponds to a mechanical separation of two electrodes.

[0086] In FIG. 1, it is seen that the first electrical conductor 21 is connected, via its distal end, to the fourth terminal 14.4 of the HVDC network unit 12, here via a fourth electrical bus 26.4 of the HVDC network unit 12. In this example, an electrical cut-off device 28.41 is interposed between the distal end of the first electrical conductor 21 and a connection 26.41 of the fourth electrical bus 26.4. Preferably, in particular for reasons of reduced cost, the electrical cut-off device 28.41 is an electrical cut-off device of the mechanical type. Thus, the first electrical conductor 21 is capable of being fully insulated, at each of its two ends, by means of an electrical cut-off device of the mechanical type which ensures the interruption of the flow of power between the first electrical conductor 21 and the rest of the infrastructure. In the particular example of Fig. 1, the fourth terminal 14.4 is electrically connected to a fourth other electrical network unit 16.4.

[0087] Although not shown in FIG. 1, it is possible to provide, at the ends of this first conductor 21, for example at each end of this first conductor, a protective inductor which can be produced in the form of a dedicated inductive component, such as a coil. Such protective inductors play the role of inductive-type current limiter, and may be provided in particular if the first conductor 21 itself has a low equivalent inductance. In a manner known per se, other parameters can be taken into account to determine the need for the presence of such a protective inductance, such as for example the type and/or the number of adjacent conductors connected to other connections of the node considered, and/or the number and/or the power of the electrical power converter(s) connected to other links of the node considered.

[0088] The link node 26.1 illustrated in FIG. 1 comprises a second link 26.12 which, in this example, is electrically connected to a second electrical conductor 22, belonging to a second power transmission line of the HVDC network unit 12, via a second power cut 28.12. In the example of FIG. 1 , we see that this second electrical conductor 22 is connected, by its distal end, to the third terminal

14.3 of the HVDC network unit 12, here via a third electrical bus 26.3 of the HVDC network unit 12. In this example, an electrical cut-off device 28.31 is interposed between the distal end of the second electrical conductor 22 and a connection of the third electrical bus 26.3.

The link node 26.1 illustrated in FIG. 1 also includes a third link 26.13. In this example, the third link 26.13 is electrically connected to another electrical network unit. The passage of a third electrical power flow is permitted through the third link 26.13. This third power flow is controlled by at least one third electrical cut-off device 28.13, associated with the third link, which has an open state and a closed state. In the example of Fig. 1, it is noted that a current cut-off device 29.1, which will be called an external cut-off device with respect to the HVDC network unit 12 considered, is electrically arranged between the electric power converter 18.1 towards the first other unit electrical network 16.1 and this same other electrical network unit 16.1 strictly speaking. In the case where the other external unit is an AC voltage network, the external cut-off device 29.1 is an AC voltage cut-off device.

The link node 26.1 illustrated in FIG. 1 has a fourth link

26.4 which is electrically connected to a third electrical conductor 23 of a third power transmission line of the HVDC network unit 12, with the interposition of a fourth electrical cut-off device 28.14. In the example, we see that this third electrical conductor 23 is connected, by its distal end, to the second terminal 14.2 of the HVDC network unit 12, with the interposition of an electrical cut-off device 28.22.

[0091] In the example illustrated in FIG. 1, it can be seen that the second terminal 14.2 is connected, within the HVDC network unit 12, only to the first terminal 14.1 of the HVDC network unit 12, here by the third electrical conductor 23. Conversely, in the example illustrated in FIG. 1, the HVDC network unit 12 comprises another electrical conductor 24 which is connected, by a first end, to the third terminal 14.3 of the HVDC network unit 12, here via an electrical cut-off device 28.32 . This other electrical conductor 24 is connected, by its second end, to the fourth terminal 14.4 of the HVDC network unit 12, here via an electrical cut-off device 28.42.

[0092] It is therefore noted that the HVDC network unit 12 of FIG. 1 is a network unit which is meshed, in the sense that it has at least two points, here two terminals, which are electrically connected by two electrical paths which are at least partly distinct. In this way, it is understood that, in the example of FIG. 1, in normal operation of the HVDC network unit 12, electrical power can be transmitted between two terminals, here the first terminal 14.1 and the fourth terminal 14.4 along two electrical paths which are at least partly distinct. However, the HVDC network unit can take other configurations, for example a star network unit, or, as in the example of Fig. 2, take the form of a point-to-point network unit.

In what follows, it will be considered that an electrical fault has appeared in the first electrical conductor 21, leading to the opening of the first electrical cut-off device 28.11. It is noted here that, with respect to FIG. 1, it is by arbitrary choice that one chooses to describe the situation of a fault in the first electrical conductor 21, and that one could similarly describe the situation of a fault in one of the other electrical conductors of the HVDC network unit 12, for example in the second electrical conductor 22.

[0094] There is shown in FIG. 3 a first embodiment of a cut-off device 28 in accordance with the teachings of the invention.

[0095] In this FIG. 3, it has been illustrated that such a cut-off device 28 is intended to be implemented in an electrical installation comprising a DC high voltage source 17 electrically connected to at least one conductor 21 of a downstream electrical line, which may comprise an airline. In the example of FIG. 3, the DC high voltage source 17 comprises for example, as seen above in relation to FIG. 1, an electric power converter 18 which is also supplied by another network unit 16, for example an alternating current network unit. The cut-off device 28 is intended to be interposed between the DC high voltage source 17 and the conductor 21 of the downstream electric line. As part of an installation according to Fig. 1, the cut-off device 28 of FIG. 3 can correspond for example to one or the other of the cut-off devices 28.11, 28.12, 28.14, 28.22, 28.31, 28.32, 28.41, 28.42 of FIG. 1 which are linked to an electrical conductor of a power transmission line without the interposition of another switching device. In the context of an installation according to FIG. 2, The cut-off device 28 of FIG. 3 can correspond for example to one or the other of the switching devices 28.1, 28.2 which are respectively linked to the electrical conductor of the power transmission line.

[0096] The cut-off device 28, designed to cut off an electric current at high DC voltage, comprises a main circuit 34, in which circulates, in a conduction configuration C_COND of the cut-off device, a nominal current which is for example greater than 500 Amps, or even greater than 1000 Amps, under a nominal continuous service voltage which is for example greater than 75,000 volts. The main circuit 34 of the cut-off device 28 extends between an upstream point 36 of the main circuit, which is intended to be electrically connected to the DC high voltage source 17, and a downstream point 38 of the main circuit, which is intended to be electrically connected to the conductor 21 of a downstream power line. In some cases, there will be no interposition of another cut-off device between the downstream point 38 and the conductor 21, or for example at the very least no interposition of another cut-off device playing a role within the framework of a process for evaluating the integrity of an electrical conductor during the closing control of the cut-off device 28.

The cut-off device 28 comprises at least a first cut-off module 40.1 comprising at least one cut-off switch 42.1 which is interposed in the main circuit 34 between a first primary point 44.1 and a first secondary point 46.1 of the main circuit 34. The first breaking module is represented here in a simplified way by a simple switch. In reality, those skilled in the art are well aware that, in the field of direct high voltage, such a cut-off switch can be associated with other elements allowing it to effectively fulfill its primary function of power cut-off. For example, a cut-off switch may have primary contacts and secondary contacts electrically in parallel. A cut-off switch may include arc blowout means. We will illustrate in the figures 9A and following that, within a cut-off module, a cut-off switch can be associated with a cut-off assistance circuit. The following description of the embodiment of FIG. 3 encompasses all these possibilities, which will however not be detailed insofar as the principle of operation which is described is not affected by the possible presence of such additional equipment in the breaking module.

The first primary point 44.1 and the first secondary point 46.1 are located in this order in the main circuit 34 between the upstream point 36 and the downstream point 38. In the example of FIG. 3, the cut-off device is represented with a single cut-off module 40.1, but it will be seen later that the cut-off device 28 may comprise several cut-off modules interposed successively in the main circuit 34 between the upstream point 36 and the downstream point 38 Usually, the cut-off switch 42.1 is capable of being controlled between an open state and a closed state to respectively determine an open state and a closed state of the first cut-off module. Typically, cut-off switch 42.1 acts as a circuit breaker. As will be seen later, the cut-off switch 42.1 of a cut-off module can be formed of several switches arranged in series and/or in parallel to ensure the current cut-off function.

The cut-off device 28 also comprises an isolation switch 48 which is interposed in the main circuit 34 of the cut-off device 28 between the upstream point 36 and the first primary point 44.1, the isolation switch 48 being capable of to be controlled between an open state and a closed state. Typically, the isolation switch 48 acts as a disconnector. Of course, nothing prevents the provision of other switches interposed in the main circuit 34 of the switching device 28 between the upstream point 36 and the first primary point 44.1, whether they are switches playing the role of a disconnector or playing another role.

[0100] As can be seen in FIG. 3, the cut-off device 28 comprises a pre-charge circuit 50 which extends between the first primary point 44.1 and the earth 52 and which comprises at least one pre-charge capacitor 54, at least one pre-charge resistor 56 and a pre-charge switch 58. It will be seen that different arrangements are possible for the pre-charge capacitor 54, the pre-charge resistor 56 and pre-charge switch 58 in pre-charge circuit 50. In the example of FIG. 3, one finds successively in the pre-charge circuit 50, going from the first primary point 44.1 to the ground 52, first the pre-charge switch 58, then the pre-charge resistor 56, then the capacitor pre-charge 54. We will see in other examples that we can also have, successively in the pre-charge circuit 50, going from the first primary point 44.1 to the ground 52, first the pre-charge capacitor 54, then the pre-charge resistor 56, then the pre-charge switch 58. According to other variants, one could have the pre-charge resistor 56 between the pre-charge capacitor 54 and the ground 52. Other variants are still possible, for example by reversing the position of the precharge capacitor 54 and of the precharge resistor 56. The precharge capacitor 54 can for example comprise a single physical component, or be formed of several distinct physical components which are then arranged in series and in parallel under the form of a capacitive system electrically equivalent to capacitor 54 illustrated.

[0101] Depending on the open or closed state of the different switches, the cut-off device 28 has different configurations, which allow the cut-off device 28 to perform different functions vis-à-vis the HVDC network unit 12 In Figures 4A-4B; 5A-5B; 6A-6D; 7A-7D, different switching sequences of the different switches have been illustrated, thus implementing different configurations of the switching device 28.

[0102] First of all, the breaking device 28 has a CJSOL isolation configuration in which the first primary point 44.1 is isolated from the upstream point 36, with the isolation switch 48 in its open state, and is isolated from the downstream point 38, with the cut-off switch 42.1 in its open state. In this configuration, which is that illustrated in FIG. 3, the downstream point 38 is therefore electrically isolated from the upstream point 36. In this way, the electrical conductor 21 of the power transmission line, which is connected to the downstream point 38, is electrically isolated from the voltage source 17 which is connected to the upstream point 36. In the embodiments comprising several cut-off modules, it will preferably be provided that, in the CJSOL isolation configuration, all the cut-off modules are in their open state. Similarly, when a breaking module comprises a switch formed by several successive cut-off switches in the main circuit 34 (see the examples described later with reference to Figs. 9A, 9B, 13 and 14A), all the cut-off switches of the module are preferably in their open state when the switchgear is in its CJSOL isolation configuration.

[0103] Preferably, when the cut-off device 28 is in its CJSOL isolation configuration, the pre-charge switch 58 is in its open state. However, it is understood that, at least in the embodiment of FIG. 4B, the pre-charge switch 58 could be in its closed state, without this calling into question the fact that the first primary point 44.1 is electrically isolated from the upstream point 36 and from the downstream point 38, nor consequently the fact that the electrical conductor 21 of the power transmission line, which is connected to the downstream point 38, is electrically isolated from the voltage source which is connected to the upstream point 36.

In a C_COND conduction configuration, the cut-off device 28 allows the nominal electric current to flow through the cut-off device 28, from the upstream point 36 to the downstream point 38, therefore from the voltage source 17, 18 towards the electrical conductor 21 of the power transmission line. The principle of this conduction configuration C_COND is, for the switching device of FIG. 3, shown in FIG. 7C. For this, the isolation switch 48, and the cut-off switch 42.1 are both in their closed state. Of course, in the embodiments comprising several cut-off modules, in the conduction configuration C_COND, all the cut-off modules 40.1, 40.2, ..., 40.n, are in their closed state. Similarly, when a cut-off module comprises a switch formed by several successive cut-off switches in the main circuit 34, all the cut-off switches of the module are in their closed state when the cut-off device 28 is in its conduction configuration C_COND . In contrast, in the C_COND conduction configuration, the pre-charge switch 58 is open to isolate the first primary point from ground.

The breaking device 28 can also be configured in a C_CH charging configuration which aims to electrically charge the pre-charge capacitor 54 of the pre-charge circuit 50. The principle of this configuration loading C_CH is, for the breaking device of FIG. 3, shown in Figure 6C. In the C_CH charging configuration, precharge switch 58 is in a closed state such that precharge capacitor 54, precharge resistor 56, and precharge switch 58 are all electrically in series. in the pre-charging circuit 50 between the first primary point 44.1 and the ground 52, while the first primary point 44.1 is electrically isolated from the downstream point 38 of the cut-off device 28 but electrically connected to the upstream point 36 to allow the charging of the pre-charge capacitor. Indeed, in this configuration, the electrical energy coming from the voltage source 17 to which the upstream point 36 is connected is capable of charging the pre-charge capacitor 54. For this, the isolation switch 48 is in its closed state and the cut-off switch 42.1 is in its open state. Of course, in the embodiments comprising several cut-off modules interposed successively in the main circuit 34 of the cut-off device 28, it will be provided that, in the loading configuration C_CH, at least one cut-off module is in an open state. Provision may be made for several cut-off modules, or even all of the cut-off modules 40.1, 40.2, ..., 40.n, to be in their open state. Similarly, when a cut-off module comprises 40.1, 40.2, ..., 4O.n, a switch formed by several successive cut-off switches in the main circuit 34, at least one cut-off switch, or even all the cut-off switches of the module are in their open state when the cut-off device 28 is in its C_CH loading configuration. Similarly, in the event of the presence of another switch between the first primary point 44.1 and the voltage source 17, these will be in their closed state.

The cut-off device 28 can also be configured in a C_PCH pre-charge configuration to allow discharge of the pre-charge capacitor in the conductor 21 of the downstream power line. In the C_PCH pre-charge configuration of the interrupter 28, the pre-charge switch 58 is in its closed state so that the pre-charge capacitor 54, the pre-charge resistor 56 and the pre-charge 58 are all electrically in series in the pre-charge circuit 50 between the first primary point 44.1 and ground 52, while the first point primary 44.1 is electrically isolated from the upstream point 36 of the cut-off device 28 but electrically connected to the downstream point 38. For this, the isolation switch 48 is in its open state and the cut-off switch 42.1 is in its closed state. Of course, in the embodiments comprising several cut-off modules, in the pre-charge configuration, all the cut-off modules 40.1, 40.2, ..., 40.n, are in their closed state. Similarly, when a cut-off module comprises a switch formed by several successive cut-off switches in the main circuit 34, all the cut-off switches of the module are in their closed state when the cut-off device 28 is in its pre-configuration. load C_PCH. The pre-charge configuration C_PCH is, for the breaking device of FIG. 3, shown in FIG. 5B.

[0107] This is in fact the case where the electrical conductor, arbitrarily the first electrical conductor 21 of FIG. 1 or Fig.2, has previously been the site of an electrical fault which resulted in its electrical isolation, by opening of the breaking devices at its two ends.

[0108] In the following, the upstream cut-off device is referred to as the one of these two cut-off devices which is located at the upstream end of the electrical conductor 21, therefore between the conductor 21 which was the subject of the electrical fault and the source voltage 17. Consequently, the downstream cut-off device is the one of these two cut-off devices which is located at the downstream end of the electrical conductor 21. In the example of FIG. 1, it can be assumed that the upstream cut-off device is, for the first electrical conductor 21, the cut-off device 28.11, the state downstream cut-off device then, for this first electrical conductor 21, the cut-off device 28.41. For a given electrical conductor, the notion of two upstream and downstream therefore depends on which end of this conductor is connected to what can be considered as a high voltage direct current voltage source. In some installations, for a given electrical conductor of a power transmission line, it will always be the same end of the conductor which can be considered as the upstream end. For example, in an installation of the type of that of FIG. 2, a first end of the electrical conductor 21 can be connected for example to a wind farm, while the other end can for example be connected to a distribution network and/or to an electricity consumer. In In this case, the end connected to the wind farm will be the upstream end. In other cases, which of the ends of the electrical conductor will be the upstream end may depend on the instantaneous state of the installation. For example, in an installation of the type illustrated in FIG. 1, which of the two ends of the first electrical conductor 21 is the upstream end may depend on the state, for example, of the other network units 16.1, 16.4 which are respectively connected respectively to each of the two ends of this first electrical conductor 21.

[0109] In FIG. 3, the upstream end of the electrical conductor 21 of the power transmission line has been illustrated as being connected to what, at least at the instant of re-closure of the line, is considered to be a voltage source DC high voltage 17. The cut-off device 28 illustrated in FIG.

3 is therefore considered, vis-à-vis the method which will be described below, as an upstream cut-off device.

Such a cut-off device can be used to implement a process for evaluating the integrity of an electrical conductor 21 in an electrical power transmission line in an electrical installation 10 comprising a main high voltage source. 17 electrically connected to the electrical conductor 21 with an upstream current cut-off device 28 interposed between the main voltage source 17 and the electrical conductor 21.

In an initial state, when the electrical conductor 21 is electrically insulated from the installation, the upstream cut-off device 28 is in a CJSOL insulation configuration. Furthermore, the electrical conductor 21 is, at a distal end, connected to a downstream electrical cut-off device which, in the initial state, is in a CJSOL insulation configuration so that, in the initial state, the conductor electrical is, except for a possible electrical fault affecting the electrical conductor 21, electrically isolated from the installation 10 and the environment.

The evaluation process envisaged comprises at least one step of precharging the electrical conductor 21 during which an auxiliary auxiliary voltage source, separate from the main voltage source 17, is connected to the electrical conductor of the electrical power transmission line, to energize the electrical conductor 21 while maintaining the electrical conductor isolated from the main voltage source 17 and from the rest of the electrical installation 10.

It will be seen that, with a cut-off device 28 according to the invention, for example that illustrated schematically in FIG. 3, the auxiliary voltage source is formed by the at least one pre-charge capacitor 54 of the pre-charge circuit 50 such that the step of pre-charging the electrical conductor 21 is carried out by bringing the charging device upstream cut in its C_PCH pre-charge configuration. Of course, care is then taken to maintain the downstream breaking device in its CJSOL isolation configuration. However, in other embodiments of an evaluation process, the auxiliary source could comprise another electrical network, or a generator, possibly with a power converter, but in any case separate from the voltage source. main 17 which delivers the nominal service voltage to the HVDC network unit 12.

The evaluation process envisaged comprises, during or after the driver pre-charging step, at least one parameter determination step comprising the determination of at least one current or voltage parameter in the electrical line. downstream, and an evaluation step during which the integrity of the electrical conductor 21 is evaluated as a function of the at least one parameter determined during the parameter determination step.

[0115] It is indeed understood that, in the event of an electrical fault affecting the electrical conductor 21, the current or voltage parameter in the line will be significantly different from that which could be found in the line in the absence of this fault. . Typically, the electrical potential of the electrical conductor 21 will be different depending on whether or not, during the implementation of the evaluation process, an electrical fault affecting the electrical conductor 21 is present. For example, with a cut-off device upstream 28 in accordance with the teachings of the invention, and provided that, before the pre-charging step, the pre-charging capacitor 54 belonging to the upstream breaking device has been charged beforehand, the pre-charging step of the conductor results in a discharge of the electrical energy contained in the capacitor of pre- load 54 to the electrical conductor 21. In the event, unless there is an electrical fault affecting the electrical conductor 21, the electrical conductor 21 is located, on the side of its downstream end, electrically isolated from the installation 10 and from the 'environment. Therefore, the electrical potential of the electrical conductor 21, which results from this discharging of the pre-charge capacitor in the electrical conductor whose state of health, and therefore the integrity, is to be assessed, will be different depending on the presence or no electrical fault affecting this electrical conductor. Also, by evaluating the electrical potential of the electrical conductor 21, an indication of the integrity of this electrical conductor 21 can be deduced therefrom.

Preferably, the evaluation process is carried out by bringing the electrical conductor 21 whose integrity is to be evaluated to a test potential level whose value is for example greater than or equal to at least 50%, preferably greater than or equal to 70% of the value of its nominal electrical potential in service, when the power line is subjected to the nominal service voltage of the HVDC network unit 12. Indeed, it appeared that for potential levels lower, an electrical fault is not necessarily detectable. For example, in the event of only partial rupture of an electrical insulator surrounding the electrical conductor, it is possible that the electrical fault only appears for a potential in the electrical conductor 21 which reaches at least the level of test potential described above. -above.

For this, it will be seen that, in the context of the use of a cut-off device 28 according to the invention, for example one of those illustrated in the figures, comprising at least one pre-charge capacitor 54, it is possible, depending in particular on the capacitance value of the pre-charge capacitor 54 with respect to the characteristic impedance, in particular the equivalent capacitance, of the electrical conductor 21, that a single pre-charge step of the conductor does not allow to reach the desired level of potential. In this case, the evaluation process can then comprise several successive pre-charging steps, separated by steps of recharging the pre-charging capacitor 54, preferably by maintaining the electrical conductor 21 electrically isolated from the main voltage source 17 , as will be described below, in order not to disturb the latter in the event of a persistent electrical fault in the electrical conductor 21. In this way, in the event that a precharging step does not make it possible to reach the desired test potential level, the evaluation process continues, without going through the conduction configuration C_COND of the power cut, that is to say without connecting the electrical conductor 21 whose integrity is to be assessed with the main voltage source 17, by a step of recharging the precharging capacitor during which the device is brought into the charging configuration C_CH, then successively, still without connecting the electrical conductor 21 whose integrity is to be assessed with the main voltage source 17, by a new electrical conductor pre-charging step and a new parameter determination step , according to a pre-charge cycle. It is noted that the step of determining the current and/or voltage parameter in the line, implemented to make it possible to evaluate the integrity of the line, can be carried out after each pre-charging step, or possibly after a predetermined number of successive pre-charge steps.

Of course, we will try not to multiply the number of precharging cycles necessary to achieve the possibility of evaluating the integrity of the conductor. To do this, it is understood that it is necessary to dimension the pre-charge capacitor 54 so that the energy which it is capable of accumulating allows, in a reasonable number of pre-charge cycles, to reach , in the electrical conductor 21 , the desired test potential level, which will for example be greater than or equal to at least 50%, preferably greater than or equal to 70% of the value of the nominal electrical potential in service in the electrical conductor 21 , when the power line is subjected to the rated service voltage of the HVDC network unit 12.

[0119] For example, one can choose to size the precharge capacitor 54 so that the energy that it is capable of accumulating makes it possible to reach, in the electrical conductor 21, and in the event that the conductor electrical is not affected by an electrical fault, the desired test potential level in a single pre-charge, or in a number of pre-charge cycles in the range from 1 to 10, preferably from 1 to 4. Of course, this sizing will depend on the equivalent capacitance of electrical conductor 21. For example, the equivalent capacitance of pre-charge capacitor 54 may be at least 10% of the equivalent capacitance of electrical conductor 21 (the capacitance equivalent of a conductor being the linear capacity of the conductor multiplied by the length of this conductor). In practice, the equivalent capacitance of the pre-charge capacitor 54 may thus be greater than 1 microfarad (pF), or even greater than 5 microfarads

By providing the possibility of having several pre-charge cycles to reach the desired test potential level, it is possible to reduce the equivalent capacitance of the pre-charge capacitor 54, and therefore its bulk and its cost. Thus, it will generally be possible to make do with a pre-charge capacitor 54 having an equivalent capacitance of less than 20 microfarads (pF), or even in certain cases an equivalent capacitance of less than 10 microfarads (pF).

The equivalent capacitance of pre-charge capacitor 54 may thus be within the range from 1 microfarad (pF) to 20 microfarads (pF), or even within the range from 5 microfarads (pF) to 20 microfarads (pF ).

For example, in a single-conductor line, the following relationship can be used to determine the dimensioning of the equivalent capacitance C ₅ 4 of the pre-charge capacitor 54:

With :

C21: the equivalent capacity of conductor 21

V ₂ itest: the desired test potential level in conductor 21

V ₁₂ : the nominal operating voltage in the HVDC network unit 12 n : a maximum number of pre-charge cycles which are authorized to reach, in the electrical conductor 21 , the desired test potential level. In all cases, the equivalent capacitance of the pre-charge capacitor 54 can be determined and/or refined empirically, for example by digital simulation or by a few experimental tests.

[0125] In certain embodiments, the pre-charge capacitor 54 must be able to withstand a voltage across its terminals which is at least equal to the nominal operating voltage in the HVDC network unit 12, for example be able to withstand a voltage at its terminals which is in the range of 1 to 2 times the nominal operating voltage in the HVDC array unit 12. disconnection in parallel with a surge protector. In such cases the pre-charge capacitor 54 must be able to hold a voltage across its terminals which is equal to the protection voltage of the surge protector, which is for example included in a range ranging from 1.5 and 1.7 times the voltage rated service in the HVDC network unit 12.

A description will now be given of a method for controlling the closing of an electrical power cut-off device in accordance with the teachings of the invention. This closing control method includes a process for evaluating the integrity of the electrical conductor. This closing control method of a cut-off device 28 is part of the general framework of an electrical protection method 100, a schematic flowchart of which is illustrated in FIG. 8.

[0127] Different steps of the closing control method will be described with reference to FIGS. 4A, 4B, 5A, 5B, 6A-6D and 7A-7D which schematically describe the different successive states of the cut-off device during such a method. piloting.

[0128] As indicated previously, FIG. 4A describes the configuration of the switching device of FIG. 3, just after a preliminary step 120 of electrical insulation of the electrical conductor 21 considered, for example following the detection 110 of an electrical fault in this electrical conductor 21. It is noted that, in FIG. 4A, the pre-charge switch 58 is in its open state. However, as shown in Fig. 4B, it could be expected to be in its closed state. In this example, the case will be described in which, just after the preliminary step 120 of electrical insulation of the electrical conductor considered, the capacitor 54 of the pre-charging circuit is in a charged state. It is then considered that the voltage across the terminals of the pre-charge capacitor 54 is equal to or of the same order of magnitude as the voltage between the electrical conductor 21 in question and the earth when the power transmission line is under its nominal service voltage. If such is not the case, the first step of the closing control method can be a step similar to the step of recharging the pre-charge capacitor 54 which will be described below. Furthermore, before initiating step 141 of pre-charging the driver, it is possible, depending on the embodiments, to provide a preparation process 130, an example of which will be described below.

In all cases, assuming that the capacitor 54 of the pre-charge circuit is in its charged state, at least one step of precharging the conductor 141 is carried out, comprising switching the cut-off device 28 to its pre-charge configuration C_PCH, described above and illustrated in FIG. 5B, to energize the electric conductor of the electric power transmission line which is arranged downstream of the downstream point 38 of the cut-off device 28. preferably, as illustrated by the succession of Figs. 5A and 5B, the driver pre-charging step 141 first includes the closing of the pre-charging switch 58, and then the closing of the cut-off module(s) 40.1, 42.1.

[0131] During or after the conductor 141 pre-charging step, in any case once the pre-charging capacitor 54 has been placed in electrical communication with the power line, the evaluation process 140 comprises at least a parameter determination step 143 comprising the determination of at least one current or voltage parameter in the main circuit 34 or in the downstream electrical line. The at least parameter to be determined can for example comprise or be selected from:

- the intensity of the current in the main circuit 34 or in the downstream electrical line, in particular in the first conductor 21,

- the derivative with respect to time of the intensity of the current in the main circuit 34 or in the downstream electric line, in particular in the first driver 21,

- the electrical potential of the first conductor 21, and/or

- the derivative with respect to time of the electric potential of the first conductor 21, or among their logical and/or arithmetic combinations.

The electric potential of the first conductor 21 can typically be determined by means of the voltage between this first conductor 21 and the earth, or by means of the voltage between this first conductor 21 and another conductor, in particular another conductor of the same electric power transmission line.

Typically, the parameter to be determined is measured, or determined from a measurement. Thus, as shown in Fig. 2, the first electrical conductor 21 and/or the main circuit 34 of the switching device 28 is preferably equipped with a measuring device 32.1, 32.2 delivering a measurement result used for determining the parameter. The measuring device may include in particular a voltmeter and/or an ammeter. It will be noted that, in certain cases, the parameter can be measured or be determined from a measurement in the link of a link node to which the electrical conductor 21 is connected via the switching device 28.

[0134] As illustrated in the example shown in FIG. 8, it is possible to provide within the evaluation process 140, a delay step 142 between the passage 141 of the switching device 28 to its pre-charge configuration and the step 143 of parameter determination. This delay step 142 can be provided for example to wait for the stabilization of the electrical conditions in the electrical conductor 21. This can for example be advantageous when the parameter to be determined is a parameter linked to the final electrical potential in the electrical conductor, resulting from the pre-charging of the conductor by passage of the cut-off device 28 to its pre-charging configuration C_PCH. Such a delay step 142 can for example have a duration of between 1 ms and 20 ms milliseconds. However, in other embodiments, for example embodiments in which the parameter to be determined relates to a variation of current or electrical potential in the electrical conductor 21 , it may be advantageous to avoid such a delay and to carrying out the parameter determination step 143 immediately after switching of the switching device 28 to its pre-charge configuration C_PCH, for example to monitor the derivative of the current or of the electrical potential in the electrical conductor 21 at the time of establishment of the current, including by the analysis of transient or oscillatory phenomena during the step 141 of pre-charging the conductor.

As indicated above, on the basis of this parameter, the evaluation process 140 can include a step 144 of evaluating the integrity of the electrical conductor 21. Typically, this evaluation step 144 can include a comparison between the parameter that has been determined and a threshold value, which may be predetermined, or may be calculated according to the conditions under which the evaluation step takes place. This threshold value may be the desired test potential level described above, or may be another value. Indeed, if the threshold value of the parameter is reached or exceeded, it can be deduced that the electrical conductor is not, or is no longer, affected by an electrical fault, thus resulting in a positive evaluation of the integrity of the electrical conductor 21. In some cases, the value determined for the parameter will make it possible to deduce that the electrical conductor remains affected by an electrical fault, thus resulting in a negative evaluation of the integrity of the electrical conductor 21. In some cases, the value determined for the parameter will make it possible to deduce that the electrical conductor remains affected by an electrical fault, thus leading to a negative evaluation of the integrity of the electrical conductor 21 , even after a single pre-charging step of the electrical conductor. However, in some cases, the value determined for the parameter does not make it possible to conclude as to the integrity of the electrical conductor. For example, this situation may be one in which the determined parameter does not make it possible to conclude that a fault is present, but that the electrical potential reached in the electrical conductor 21 following the precharging step has not reached the test electric potential value.

Thus, typically, after at least one step 141 of pre-charging the conductor, the complete closing of the current breaking device by passing the current breaking device to its conduction configuration C_COND is continued if a voltage value in the main circuit 34 of the cut-off device 28, or in the downstream electrical line, exceeds a threshold value.

[0137] In general, the method for controlling the switching device may include a decision step, during which it is decided, depending on the at least one parameter determined during the parameter determination step, to the continuation or not of the complete closing of the current breaking device by passage of the current breaking device to the conduction configuration C_COND. Typically, this complete closing continuation decision step therefore results in a positive continuation decision, if the evaluation of the integrity of the electrical conductor could be carried out and is positive. On the other hand, this step of deciding to continue with full closure therefore results in a negative continuation decision, if the evaluation of the integrity of the electrical conductor could not be carried out or is negative.

In the example illustrated, the evaluation step and the decision step are one and the same step 144. For example, this step can include a comparison between an electrical potential value of the first conductor 21, determined in determining step 143, and a threshold value, for example the desired test potential level described above.

Of course, one and/or the other of the evaluation step and the decision step can be based on the determination of several parameters. Furthermore, provision can be made for the evaluation step and the decision step to be based on the determination of different parameters, or on the basis of partly different sets of parameters.

[0140] If the continuation decision is positive, then the method triggers a continuation 160 of the complete closing of the cut-off device 28.

An example of a process 160 for continuing the complete closing of the breaking device 28 is illustrated by the succession of Figs. 7A to 7C. According to this example, the cut-off device 28 passes for example from the state of FIG. 7A, corresponding to the breaking device 28 in its C_PCH precharge configuration, in the state of FIG. 7C corresponding to cut-off device 28 in its conduction configuration C_COND. Preferably, as illustrated in FIG. 7B, this can be done in particular by first providing the opening 161 of the pre-charge switch 58 before proceeding with the closing 163 of the isolation switch 48 of the cut-off device 28 which makes it possible to bring the device into its conduction configuration C_COND. It will be noted that, in the example illustrated, the isolation switch 48 is the one which is closed last to reach the conduction configuration C_COND.

[0142] In FIG. 8, the process 160 of continuing the complete closing of the breaking device 28 ends with the step 163 of switching the breaking device 28 to its conduction configuration C_COND. As described above, the process 160 of continuing the complete closing of the breaking device 28 may include additional steps, in particular steps prior to step 163 of switching the breaking device 28 to its conduction configuration C_COND. These additional steps 162 can for example allow a reconfiguration of the cut-off device 28, in particular with a view to enabling it to be ready for a new power cut in the event of detection of an electrical fault affecting the electrical conductor 21.

[0143] As indicated above, provision can be made for the decision to continue complete closing of the cut-off device 28 to be conditional on the step 144 of evaluating the integrity of the electrical conductor 21 having been able to be carried out in satisfactory conditions, in particular vis-à-vis the electrical potential reached in the electrical conductor 21 following the pre-charging step. If this electrical potential is insufficient to be able to decide positively as to the integrity of the electrical conductor, provision can be made for the decision step to remain negative, without this necessarily leading to the conclusion that the electrical conductor 21 would necessarily be affected by a electrical fault.

If the decision step 144 is negative, the method can continue, without going through the conduction configuration C_COND of the current breaking device, with a step 180 of recharging the pre-charge capacitor during which the device is brought into the charging configuration C_CH, then successively by a new driver pre-charging step 141 , a new parameter determination step 143 , and a new evaluation and/or decision step 144 , according to a new pre-charge cycle. Provision can be made for this new pre-charging cycle to be implemented only if the evaluation step has not previously resulted in a negative evaluation of the integrity of the electrical conductor.

It is understood that this pre-charge cycle may repeat itself several times in succession as long as the evaluation and/or decision step is not positive, therefore as long as the method does not continue with a process 160 of complete closing of the breaking device 28.

Preferably, the number of pre-charge cycles will be limited for a given attempt to re-close the cut-off device 28.

[0147] This has been represented in FIG. 8 by a verification step 170 of the number of pre-charges performed. For example, each time the evaluation and/or decision step 144 is not positive, it is possible to increment a counter by one unit, and verify, during the verification step 170, that the value of this counter does not exceed a maximum value.

If the verification step 170 of the number of pre-charges performed reveals that a maximum number has been exceeded, the control process can be terminated 190, without having resulted in complete re-closing of the cut-off device. Thus, if, after several pre-charge cycles, the decision step is negative, the closing control process is interrupted. In this case, it is preferable to bring the cut-off device 28 into its CJSOL isolation configuration. Generally, this hypothesis materializes in the event of the presence of a persistent fault affecting the electrical conductor 21 , requiring intervention.

If the verification step 170 of the number of pre-charges performed reveals that a maximum number has not been exceeded, the control method can restart a new pre-charge step 141 of the driver 21, but after having carried out a recharging step 180 of the pre-charge capacitor 54.

Typically, the recharging step 180 of the pre-charge capacitor 54 includes:

- the closure of the isolation switch 48 and the closure of the pre-charge switch 58, maintaining the cut-off switch 40.1, 42.1 in its open state, to charge the pre-charge capacitor 54, this which is illustrated in Fig. 6C; - after said closing of the pre-charge switch, the reopening of the isolation switch 48, which is illustrated in FIG. 6D.

[0151] As a preliminary, starting from the pre-charge configuration C_PCH as illustrated in FIG. 6A, the at least one breaking module 40.1 will have been opened, which is illustrated in FIG. 6B, therefore before switching the cut-off device into its recharging configuration illustrated in FIG. 6C.

Above, we considered the case in which, just after the preliminary step 120 of electrical insulation of the electrical conductor considered, the capacitor 54 of the pre-charging circuit 50 is in a charged state. However, in certain embodiments, the implementation of the cut-off device 28 will cause that, just after the preliminary step 120 of electrical insulation of the electrical conductor considered, the capacitor 54 of the pre-charging circuit is in a discharged state. , or insufficiently charged. In this case, provision will advantageously be made for the control method to include, after the preliminary step 120 of electrical insulation of the electrical conductor in question but before a first step of pre-charging the conductor 141 , a preliminary step 132 of recharging the capacitor of pre-load, for example within the preparation process 130. The preparation process 130 can also include other preparation steps 131.

[0153] FIG. 3 illustrates a particularly simple embodiment of a switching device according to the invention.

We will now describe embodiments of a switching device according to the invention which are more complex, while presenting the same general architecture as that of FIG. 3.

As will be seen in what follows, some of these embodiments of a cut-off device 28 will comprise a single cut-off module 40.1 between the first primary point 44.1 and the downstream point 38. Other embodiments will comprise, downstream of the first cut-off module 40.1 in the main circuit 34 of the cut-off device 28, at least one last cut-off module 40.n comprising at least one cut-off switch 42.n interposed in the main circuit 34 between a last primary point 44.n, downstream of the first secondary point 46.1, and a last secondary point 46.n of the circuit main 34. The cut-off switch 42.n of the last cut-off module 4O.n is capable of being controlled between an open state and a closed state to respectively determine an open state and a closed state of the last cut-off module 4O. not. Among these embodiments comprising at least two successive cutoff modules in the main circuit 34 between the first primary point 44.1 and the downstream point 38, certain cutoff devices 28 will have only two cutoff modules, between the first primary point 44.1 and the downstream point 38, namely therefore a first cut-off module 40.1 and a last cut-off module 40.n, the last cut-off module then also being the second cut-off module. On the contrary, some cut-off devices 28 will include, in the main circuit 34 of the cut-off device 28, between the first cut-off module 40.1 and the last cut-off module 40.n, at least one additional cut-off module 40.2,... , comprising at least one cut-off switch 42.2, ..., interposed in the main circuit 34 between an additional primary point 44.2, ..., downstream of the first secondary point 46.1, and an additional secondary point 46.2, ..., of the main circuit 34, upstream of the last primary point 44.n, and the cut-off switch 42.2, ..., of the additional module 40.2, ..., being able to be controlled between an open state and a closed state to respectively determine an open state and a closed state of the additional breaking module 40.2, ...,. Thus, such a cut-off device 28 may comprise a single additional cut-off module interposed in the main circuit between the first cut-off module and the last cut-off module, or several additional cut-off modules successively interposed, in the main circuit, between the first break module and the last break module.

It will be seen that, for two successive cut-off modules 4O.i, 4O.i+1 in the upstream-downstream direction in the main circuit 34, the primary point 44.i+1 of the one downstream may be electrically merged with the secondary point 46.i of that which is upstream, in the sense that the two points are always at the same electric potential.

We will also describe embodiments in which the cut-off device 28 comprises at least one cut-off module 4O.i (i=1, 2, ..,) comprising a cut-off assistance circuit 7O. i (i=1, 2, ..,) which extends electrically in derivation from the cut-off switch 42.i (i=1, 2, ..,) and from the main circuit 34 between the first primary point 44.i (i=1, 2, and a secondary point 46.i (i=1, 2, of the main circuit 34.

[0158] Such a cut-off assistance circuit 7O.i is a device which, when the cut-off module passes from its closed state to its open state, will promote the cut-off of the electric current through the switch of cutoff 42.i of the cutoff module 4O.i considered. Typically, such a cut-off assistance circuit 70.i will make it possible to transiently reduce the intensity of the electric current in the cut-off switch 42.i with which it is electrically associated in parallel, or even will allow, in a transient way , to tend to the cancellation, or the inversion of the direction of circulation, of the electric current in the cut-off switch 42.i with which it is electrically associated in parallel. In such embodiments, it will be particularly advantageous if, in a C_C cutoff configuration, the cutoff device 28 is configured such that at least one pre-charge capacitor 54.i (i=1, 2, . .,) of the pre-charge circuit is also part of the cut-off assistance circuit 7O.i. Indeed, in this C_C cutoff configuration, the pre-charge capacitor 54.i will advantageously also be used to ensure the function of facilitating the cutoff. In this way, the same electrical component, the pre-charge capacitor 54.i will be used for two different functions, which will be a source of cost and bulk reduction for a cut-off device 28 having both a circuit of cut-off assistance and a pre-charge circuit as described above.

In general, this can be implemented as follows. In each of the embodiments, for at least one cut-off module 4O.i, a cut-off assistance circuit 7O.i comprises, successively and in this order from the primary point 44.i associated with the module considered, the at least one pre-charge capacitor 54.i and an activation switch 72.i, with a tapping point 76 between the two in the cut-off assistance circuit 7O.i. Thus, it can be defined that the pre-charge circuit comprises a first section, which is common with the cut-off assistance circuit 70.i, which extends between the first primary point 44.1 and the tapping point 76 and which comprises the at least one pre-charge capacitor 54.i, and a second section, distinct from the circuit cut-off assistance 7O.i, which extends between the tapping point 76 and the earth 52 and in which the pre-charge switch 58 is interposed.

[0160] In the embodiments which will be described, the preparation process 130 within the control method may include a preparation step during which all current flow is cut off in the cut-off assistance circuit between the tapping point and the secondary point, for example using a switch placed between these two points.

[0161] Illustrated in FIG. 9A a first embodiment of a cut-off device 28 whose cut-off module 40.1 comprises both a cut-off assistance circuit 70.1 and a pre-charge circuit 50 as described above. This embodiment comprises a single cut-off module 40.1 between the first primary point 44.1 and the downstream point 38. This embodiment of a cut-off device 28 extends between an upstream point 36 and a downstream point 38 and can therefore be used instead of the embodiment illustrated in FIG. 3. Such a breaking module is described in more detail in document WO 2020/136340 to which reference may be made for a detailed description.

[0162] This single cut-off module 40.1 comprises a cut-off switch

42.1 having a primary switch 60.1, mechanical, and a secondary switch 62.1, mechanical, interposed successively in the main circuit 34 between the first primary point 44.1 and the first secondary point 46.1 associated with this single cut-off module 40.1, but on both sides another from a first intermediate point 64.1 of the main circuit 34 which corresponds to the cut-off module 40.1. The two mechanical switches primary 60.1 and secondary

62.1 can each be controlled between an open state and a closed state. As the breaking module 40.1 is here unique in the breaking device 28, the first secondary point 46.1 of the breaking module 40.1 can be considered as electrically coincident with the downstream point 38 of the breaking device 28, in the sense that the two points are always at the same electrical potential.

In this embodiment, the cut-off switch 42.1 comprises: - a primary surge protector 66.1 arranged in parallel with the primary switch 60.1 between the first primary point 44.1 and the first intermediate point 64.1,

- A secondary surge protector 68.1 arranged electrically in parallel with the secondary switch 62.1 between the first intermediate point 64.1 and the first secondary point 46.1.

Such surge protectors make it possible to limit the amplitude of the potential difference across the terminals of the switch in parallel with which they are arranged. Among surge arresters, surge arresters are known in particular, which may in particular comprise varistors (or varistors) and “TVS” (Transient Voltage Suppressor) diodes, such as “Transil™” diodes. In particular, the primary surge arrester 66.1 and/or the secondary surge protector 68.1 can each comprise a metal oxide varistor (or MOV, meaning “metal oxide varistor”).

In this embodiment, the cut-off assistance circuit 70.1 of the cut-off switch 42.1 extends between the first primary point 44.1 and the first secondary point 46.1 in the form of a capacitive buffer circuit which extends electrically in parallel with the assembly formed by the primary switch 60.1 and the secondary switch 62.1, and electrically in parallel with the assembly formed by the primary surge protector 66.1 and the secondary surge protector 68.1, and which comprises a switch of activation 72.1 and a buffer capacitor which is here formed by the pre-charge capacitor 54.1. Preferably, in this embodiment, the capacitive buffer circuit forming a cut-off assistance circuit 70.1 does not include a dedicated inductive component. The capacitive buffer circuit forming a cut-off assistance circuit 70.1 may comprise a tertiary surge protector 74.1 arranged in parallel with the activation switch 72.1, for example directly across the terminals of the activation switch 72.1.

It can be seen that the cut-off assistance circuit 70.1 comprises, successively and in this order from the first primary point 44.1, the at least one pre-charge capacitor 54.1 and an activation switch 72.1, with a tapping point 76 between the two in the cut-off assistance circuit 70.1. The pre-charge circuit 50 comprises a first section, which is common with the cut-off assistance circuit, which extends between the first primary point 44.1 and the tapping point 76 and which comprises the at least one pre-charge capacitor 54.1 . The pre-charge circuit 50 comprises a second section, separate from the cut-off assistance circuit 70.1, which extends between the tapping point 76 and the earth 52 and in which the pre-charge switch 58 is interposed. Note that the pre-charge resistor 56 of the pre-charge circuit 50 is arranged in the second section, separate from the cut-off assistance circuit 70.1, which extends between the tapping point 76 and the ground 52 , therefore outside of the cut-off assistance circuit 70.1. It is understood that, in this second section which extends between the tapping point 76 and the earth 52, the pre-charge resistor 56 of the pre-charge circuit 50 could be arranged on one side or the other of the pre-charge switch.

Note that, in this embodiment, which includes a tertiary surge protector 74.1 across the terminals of the activation switch 72.1, a configuration switch 78.1 is provided in the section of the cut-off assistance circuit which is separate from the pre-charge circuit 50. The configuration switch 78.1 is arranged between the tertiary surge protector 74.1 and the downstream point 38. This configuration switch 78.1 is closed in a cut-off configuration C_C of the cut-off device 28, during which the cut-off assistance circuit 70.1 is active to interrupt the flow of current in the cut-off switch 42.1 during opening. This configuration switch 78.1 is in its open state in the C_CH charging and C_PCH pre-charging configurations of the cut-off device 28, to prevent the electrical conductor 21, connected to the downstream point 38, from being able to discharge through the circuit cut-off assistance 70.1, in particular through the tertiary surge protector 74.1. Preferably, this configuration switch 78.1 is in its closed state in conduction configuration C_COND to anticipate a possible need to re-open the cut-off device 28.

[0168] In this embodiment, it is necessary that, to perform the cut-off, the pre-charge capacitor 54 is in a discharged state at the moment when it is desired that it operates in the context of the assistance. at the cut. It is therefore necessary to provide a discharge circuit for the pre-charge capacitor 54.1. Such a discharge circuit (not shown in the figures) can be a passive discharge circuit, comprising no active component, for example comprising a discharge resistor arranged in parallel with the pre-charge capacitor 54. Preferably, such a discharge resistor has a high electrical resistance value so that the dipole which consists of the pre-charge capacitor 54 and the discharge resistor arranged in parallel, has a significant time constant with respect to an electrical cut-off delay in the secondary switch 62.1, for example a time constant greater than 50 milliseconds, preferably greater than 100 milliseconds. Another type of discharge circuit may include at least one active component, such as a controlled switch. Thus, a discharge circuit could comprise a controlled switch which would be arranged directly in electrical series with the discharge resistor mentioned above, all of these two components being in parallel with the pre-charge capacitor 54.1. When the controlled switch would be switched to a closed state letting the current flow, a discharge circuit would form between the two plates of the pre-charge capacitor 54.

In a method for controlling a switching device 28 according to FIG. 9A, in order to bring the device from its closed state to its open state, a step is provided comprising the mechanical opening of the primary switch 60.1 and of the secondary switch 66.1. The two switches can be opened mechanically simultaneously, or successively in any order. Such a step of opening the two switches can be triggered in the presence of an electrical fault in the electrical installation, in particular in the electrical conductor of the downstream line which is connected to the downstream point 38. It is possible that the mechanical opening of the two switches 60.1, 66.1 of the cut-off switch 42.1 does not allow, on its own, the electrical opening in the sense of interrupting the passage of current through the cut-off device 10, by the fault of the establishment of an electric arc through each of two switches 60.1, 66.1. In this hypothesis, the method provides for cutting off the current in the open primary switch 60.1 to cause the appearance, at the terminals of the primary switch 60.1, of a voltage greater than the transition voltage of the primary surge protector 66.1 specific to the switch to a current-conducting mode. To break the current in the open primary switch 60.1, use can be made of an oscillation circuit as described in one or other of documents WO-2020/136340, WO-2015/103857, EP-3,091,626, CN-103,296,636 and WO-2012/100831, combining in series a capacitor and a dedicated inductive component , to create an oscillating current to impose a zero crossing of the current in the open primary switch 60.1. The current cut in the open primary switch 60.1 can be obtained by other means, in particular by suitable sizing of the primary switch 60.1, even if this sizing leads to a bulkier and/or more expensive primary switch. than that which can be used if an oscillation circuit is present. Once obtained, this breaking of the current through the primary switch 60.1 forces the current through the breaking device 28 to charge the pre-charging capacitor 54.1, causing a voltage rise across its terminals, which results in the appearance of this same voltage at the terminals of the primary surge protector 66.1, and therefore of the same voltage at the terminals of the primary switch 60.1. In the event of a high fault current, this voltage reaches the transition voltage of the primary surge protector 66.1, which then sees its resistance vary to limit the increase in voltage, which reaches a plateau. At this stage, it is considered that the primary surge protector 66.1 becomes conductive for the current. Thus, it can be considered that, from this moment, the current through the cut-off device 28 passes through the primary surge protector 66.1 but continues to circulate through the secondary switch 62.1 due to the presence of an arc electric between the contacts of the latter. To cause the breaking of the electric arc in the secondary switch 62.1, the cut-off assistance circuit is activated by closing the activation switch 72.1. It will be assumed that the configuration switch will have been previously brought into its closed state, otherwise it can be done at this instant. This allows, in the cut-off assistance circuit 70.1, the passage of a clean current to charge the pre-charge capacitor 54.1 and to shed the current in the secondary switch 62.1. In the initial state, the pre-charge capacitor 54.1 is discharged, for example by the presence of the discharge circuit. In other words, the cut-off device 28 is configured so that, in the initial state, that is to say on the switching of the activation switch 72.1 to allow passage, in the cut-off assistance circuit 70.1, of a current capable of charging the pre-charge capacitor 54.1, the pre-charge capacitor 54.1 is discharged. Because of this, and because of the presence of a potential difference across the terminals of the primary surge protector 66.1, the current through the device 28 switches to the cut-off assistance circuit 70.1 to charge the pre-charge capacitor 54.1 . During the charging time of the pre-charging capacitor 54.1, the current through the cut-off device 28 is essentially conducted by the cut-off assistance circuit 70.1, which has the consequence of lowering or even d cancel the current which circulated through the secondary switch 62.1, which it should be remembered is in a state of mechanical cut-off, with its contacts separated from each other. This reduction, or even cancellation, of the current through the secondary switch 62.1 will advantageously cause the extinction of the electric arc in the secondary switch 62.1. It is then considered that the secondary switch 62.1 is electrically open and that a voltage can appear at its terminals without risk of re-ignition of the electric arc. This voltage is reflected across the terminals of the secondary surge protector 68.1, which can then play its role of limiting the voltage across the terminals of the secondary switch. It can then be considered that the cut-off device 28 is open, since only a leakage current can flow through the device 28 passing through the primary surge protector 60.1 and through the secondary surge protector 62.1. For this, it is therefore judicious to choose the primary surge protector 60.1 and the secondary surge protector 62.1 so that the sum of their transition voltage is greater than the nominal voltage of the installation.

In the example, the pre-charge capacitor 54.1 is the only capacitor of the cut-off assistance circuit 70.1, in the sense that there is no capacitor in the section of the cut-off assistance circuit. cutoff 70.1 which is separate from pre-charge circuit 50, here between tapping point 76 and secondary point 46.1. However, depending on the capacitive needs for on the one hand the precharge operation and on the other hand the cut-off assistance operation, it is possible to have, in addition to the precharge capacitor 54.1 which is arranged in the section of the pre-charge circuit 50 which is common with the cut-off assistance circuit 70.1, at least one other capacitor, this other capacitor being arranged in the section of the cut-off assistance circuit 70.1 which is separate from circuit pre-load 50, here between the tapping point 76 and the secondary point 46.1. In any case, the pre-charge capacitor 54.1 can take the form of a single physical component, or be formed of several physical components which can be arranged electrically in series and/or in parallel so as to form an equivalent capacitive system. electrically to capacitor 54.1 shown.

For this embodiment of a cut-off device 28 illustrated in FIG. 9A, there is illustrated in FIG. 9B a table in which there is represented, for each of the configurations described above of a switching device 28 according to the invention, the state of the various switches in the configuration represented. Each line of the table corresponds to one of these configurations, and the columns of the table correspond to the switches of the breaking device 28, designated by the corresponding references used in the figures and in the text above. The open state is represented by the number 0, and the closed state is represented by the number 1. In the absence of any indication, the switch can be in one or the other of its states, with the possibility that there is a preferential state depending on the installation considered.

Thus, for this embodiment of a switching device 28 illustrated in FIG. 9A, the conduction configuration C_COND is obtained by bringing the isolation switch 48 and the cut-off switch 42.1, the latter being here formed by the primary switch 60.1 and the secondary switch 60.2, in their closed state. The pre-charge switch 58 can for example be in its open state. Preferably, enable switch 72.1 is in its open state and configuration switch 78.1 is in its closed state.

In this embodiment, the cutoff configuration C_C involves bringing the pre-charge switch 58 into its open state, then the configuration switch 78.1 into its closed state. We saw above that the cut-off switch 42.1, namely here the primary switch 60.1 and the secondary switch 60.2, is brought into its open state, and the activation switch 72.1 is brought into its closed state by so that the cut-off assistance circuit 70.1, which includes the pre-charge capacitor 54.1, can play its cut-off assistance function. Preferably, for example once the break has been obtained, the isolation switch 48 is brought into its open state. For this embodiment of a switching device 28 illustrated in FIG. 9A, the CJSOL isolation configuration is obtained by bringing the isolation switch 48, and the cut-off switch 42.1, namely here the primary interior

60.1 and the secondary switch 60.2, in their open state. At least one of enable switch 72.1 and configuration switch 78.1 is in its open state. For example, the pre-charge switch 58 is in its open state.

The charging configuration C_CH which aims to electrically charge the pre-charge capacitor 54 of the pre-charge circuit 50 is obtained by bringing the isolation switch 48 and the pre-charge switch 58 to their state closed, the cut-off switch 42.1, namely here the primary interior 60.1 and the secondary switch 60.2, being brought into their open state just as the configuration switch 78.1 is also in its open state. Preferably, the activation switch 72.1 is also in its open state.

The pre-charge configuration C_PCH to allow discharge of the pre-charge capacitor 54.1 in the conductor of the downstream electric line is obtained by bringing the isolation switch 48 into its open state, and by bringing the pre-charge switch 58 and cut-off switch 42.1, namely here the primary interior 60.1 and the secondary switch 60.2, in their closed state. Preferably, to anticipate a possible need to re-open the cut-off device 28, provision can be made to bring the configuration switch

78.1 in its closed state, but the activation switch 72.1 then being in its open state.

It is understood that, to ensure the pre-charging of the electrical conductor 21 of the downstream line which is electrically connected to the downstream point 38, this embodiment of the cut-off device illustrated in FIG. 9A is driven in the manner described with reference to FIG. 3.

[0178] It is noted that it is possible to provide, before a first step of pre-charging the electrical conductor 21, a preparation step during which all current flow is cut off in the cut-off assistance circuit 70.1 between the stitching point 76 and the secondary point 46.1. This can be done for example by opening the activation switch 72.1. [0179] Illustrated in FIG. 10A a variant embodiment of the switching device 28 of FIG. 9A. The alternative embodiment of FIG. 10A is identical to that of FIG. 9A, except for the presence of a bypass circuit 80 which extends, electrically in parallel with the main circuit 34, between the first primary point 44.1 and a bypass point 82 arranged between the last secondary point, here the first secondary point 46.1 since this embodiment comprises only a single cut-off module 40.1, and the downstream point 38. In this bypass circuit is interposed a bypass switch 84 which is in a closed state in the C_PCH precharge configuration and in an open state in the C_CH charging, CJSOL isolation, C_C cutoff, and also in the C_COND conduction configuration. The bypass circuit 80 makes it possible to ensure, for the pre-charge configuration C_PCH, the pre-charge of the electrical conductor 21 of the downstream power transmission line, through a circuit having the most parasitic inductance possible low. The presence of the bypass circuit 80 makes it possible to move the configuration switch 78 to put it in the main line 34 between the first secondary point 46.1 and the bypass point 82. In this position in the breaking device, the configuration switch 78 is closed in the conduction configuration C_COND, and in the breaking configuration C_C of the breaking device 28. In this position in the breaking device, the configuration switch 78 is open in the loading configurations C_CH and pre-charge C_PCH of the cut-off device 28, to prevent the electrical conductor 21, connected to the downstream point 38, from being able to discharge through the cut-off assistance circuit 70.1. This embodiment, which makes it possible to move the configuration switch 78 outside the cut-off assistance circuit 70.1, makes it possible to have a cut-off assistance circuit 70.1 having the lowest possible parasitic inductance.

[0180] As can be seen in FIG. 10B, the state of the other switches in the different configurations is the same as for the previous variant.

[0181] Illustrated in Figs. 11 A and 11 B two variants of a switching device according to the invention which are derived from a switching device architecture which is described in particular in the documents WO-2016/003357 and WO-201 7/116296, to which will refer in more detail to the operation of the cut-off assistance circuit 70.1. In the switching devices 28 of Figs. 11 A and 11 B, there is therefore a main circuit 34, in which a nominal direct current flows in a conduction configuration C_COND of the breaking device, the main circuit 34 extending between an upstream point 36 intended to be electrically connected to a DC high voltage source 17 and a downstream point 38 intended to be electrically connected to a conductor 21 of a downstream electric power transmission line. These two embodiments here comprise a single cut-off module 40.1 comprising at least one cut-off switch 42.1 interposed in the main circuit 34 between a first primary point 44.1 and a first secondary point 46.1 of the main circuit 34. The first primary point 44.1 and the first secondary point 46.1 are located in this order in the main circuit 34 between the upstream point 36 and the downstream point 38. These two variant embodiments comprise an isolation switch 48, interposed in the main circuit 34 between the upstream point 36 and the first primary point 44.1. In this architecture, there is provided, in parallel with the cut-off module 40.1, a cut-off assistance circuit 70.1 which extends between the primary point 44.1 and the secondary point 46.1 which correspond to the cut-off module considered. In a C_C cut-off configuration, the cut-off assistance circuit 70.1 is provided to promote the extinction of an electric arc which may form between the terminals of the cut-off switch 42.1 when it opens. For this, the cut-off assistance circuit 70.1 comprises, between the primary point 44.1 and the secondary point 46.1 which correspond to the cut-off module considered, at least one dedicated inductive component 90.1, a controlled voltage source 92.1 and a capacitor 54.1. In this architecture, the cut-off assistance circuit 70.1 therefore forms an LC circuit in which current oscillations can be forced. The controlled voltage source 92.1 is controlled to create current alternations of increasing intensity in the cut-off assistance circuit 70.1, until these current oscillations exceed in intensity the fault current in the circuit breaker. cut 42.1. Thanks to such an oscillation, the cut-off assistance circuit 70.1 ends up injecting into the main circuit 34, through the cut-off switch, a counter-current in the opposite direction to the fault current, and d intensity greater than the fault current, causing the current to pass through zero in the cut-off switch 42.1, which leads to the extinction of the electric arc. It is further noted that the cut-off module 40.1 of the embodiment of FIG. 11 A comprises a surge protector 73.1 which is arranged electrically in parallel with the assembly comprising the capacitor 54.1, the controlled voltage source 92.1, and a configuration switch 78.1 which will be detailed later, to limit the voltage across this assembly. For its part, the breaking module 40.1 of the embodiment of FIG. 11B includes a surge protector 75.1 which is electrically arranged in parallel with capacitor 54.1 to limit the voltage across capacitor 54.1.

[0182] Unlike the basic architecture described in particular in documents WO-201 6/003357 and WO-2017/116296, the switching devices 28 of Figs.

11 A and 11 B include a pre-charge circuit 50 which extends between the first primary point 44.1 and ground 52 and which includes at least one pre-charge capacitor 54.1 at least one pre-charge resistor 56 and a pre-charge switch 58. As seen in the figures, in a C_C cut-off configuration, the cut-off device 28 is configured such that the pre-charge capacitor 54.1 of the pre-charge circuit 50 forms part of the cut-off assistance circuit 70.1, in which it acts as the capacitor of the LC circuit intended to generate the oscillations.

The pre-charge circuit 50 comprises a first section, which is common with the cut-off assistance circuit 70.1, which extends between the first primary point 44.1 and a tapping point 76 and which comprises the at least one pre-charge capacitor 54.1. The pre-charge circuit 50 comprises a second section, distinct from the cut-off assistance circuit 70.1, which extends between the tapping point 76 and the earth 52 and in which the pre-charge switch 58 is interposed. Note that the pre-charge resistor 56 of the pre-charge circuit 50 is, in these two variants, arranged in the second section of the pre-charge circuit 50 which extends between the tapping point 76 and the earth. 52, therefore outside the cut-off assistance circuit 70.1.

[0184] In the variant of FIG. 11 A, the controlled voltage source 92.1, which comprises for example a point of controlled thyristors and capacitors, is arranged in the part of the cut-off assistance circuit 70.1 which is common with pre-charge circuit 50, here between at least one pre-charge capacitor 54.1 and tapping point 76. In the variant of FIG. 11B, the controlled voltage source 92.1, is arranged in the part of the cut-off assistance circuit 70.1 which is separate from the pre-charge circuit 50, here between the tapping point 76 and the secondary point 46.1.

[0185] Unlike the basic architecture described in particular in documents WO-201 6/003357 and WO-2017/116296, the switching devices 28 of Figs. 11 A and 11 B comprise a configuration switch 78.1 in the section of the cut-off assistance circuit 70.1 which is separate from the pre-charge circuit 50. The configuration switch 78.1 is arranged between the tapping point 76 and the downstream point 38. This configuration switch 78.1 is closed in a C_C cut-off configuration of the cut-off device 28, during which the cut-off assistance circuit 70.1 is active to interrupt the flow of current in the 42.1 cut being opened. This configuration switch 78.1 is open in the C_CH charging and C_PCH pre-charging configurations of the cut-off device 28, to prevent the electrical conductor 21, connected to the downstream point 38, from being able to discharge through the assistance circuit at cutoff 70.1.

[0186] Illustrated in FIG. 11 C a table which reads in the same way as that of FIG. 9B, in which there is shown, for each of the configurations described above, a switching device 28 according to one or other of the variants of Figs. 11 A and 11 B, the state of the various switches in the configuration. In addition to the C_COND conduction, CJSOL isolation and C_C cutoff configurations, there is therefore a C_CH charging configuration in which the pre-charge switch 58 is in a closed state so that the pre-charge capacitor 54.1 , pre-charge resistor 56 and pre-charge switch 58 are all electrically in series in pre-charge circuit 50 between first primary point 44.1 and ground 52, while first primary point 44.1 is electrically isolated from the downstream point 38 of the cut-off device 28, in particular by the opening of the cut-off switch 42.1, but electrically connected to the upstream point 36, by the closing of the isolation switch 48 to allow the charging of the capacitor of pre-load 54.1. We find a pre-charge configuration C_PCH in which the pre-charge switch 58 is in its closed state so that the pre-charge capacitor 54.1, the pre-charge resistor 56 and the pre-charge switch 58 are all electrically in series in the pre-charge circuit -load 50 between the first primary point 44.1 and the ground 52, while the first primary point 44.1 is electrically isolated from the upstream point 36 of the cut-off device, by the opening of the isolation switch 48, but electrically connected to the downstream point 38, by closing cut-off switch 42.1 to allow discharge of pre-charge capacitor 54.1 into conductor 21 of the downstream power line.

[0187] Illustrated in FIG. 12A a switching device according to the invention which is derived from a switching device architecture which is described in particular in the document K. TAKATA et. para. " HVDC Circuit Breakers for HVDC Grid Applications”, CIGRE AORC 2014, to which reference will be made in more detail for the operation of the breaking assistance device. In the breaking device 28 of Figs. 12A, there is therefore a circuit main circuit 34, in which a nominal direct current flows in a conduction configuration of the breaking device, the main circuit 34 extending between an upstream point 36 intended to be electrically connected to a direct high voltage source 17 and a downstream point 38 intended to be electrically connected to a conductor 21 of a downstream electric power transmission line.This embodiment here comprises a single cut-off module 40.1 comprising at least one cut-off switch 42.1 interposed in the main circuit 34 between a first primary point 44.1 and a first secondary point 46.1 of the main circuit 34. The first primary point 44.1 and the first secondary point 46.1 are located in this o rdre in the main circuit 34 between the upstream point 36 and the downstream point 38. This variant embodiment comprises an isolation switch 48, interposed in the main circuit 34 between the upstream point 36 and the first primary point 44.1. In this architecture, there is provided, in parallel with the cut-off module 40.1, a cut-off assistance circuit 70.1 which extends between the primary point 44.1 and the secondary point 46.1 which correspond to the cut-off module considered. In a C_C cut-off configuration, the cut-off assistance circuit 70.1 is provided to promote the extinction of an electric arc which may form between the terminals of the cut-off switch 42.1 when it is opened. For this, the cut-off assistance circuit 70.1 comprises, between the primary point 44.1 and the secondary point 46.1 which correspond to the cut-off module considered, at least one dedicated inductive component 90.1, a capacitor 54.1 and an activation switch 72.1. In this architecture, cut-off assistance circuit 70.1 therefore forms an LC circuit in which current oscillations can be forced, here by discharging capacitor 54.1. Indeed, starting from a charged capacitor 54.1, the closing of the activation switch causes the discharge of the capacitor in the cut-off assistance circuit 70.1 which forms an LC circuit. This discharge takes the form of an oscillatory current. In a known manner, this LC-type cut-off assistance circuit 70.1 is dimensioned, in particular in terms of capacitance and inductance, such that the current oscillations exceed in intensity the fault current in the cut-off switch 42.1. Thanks to such an oscillation, the cut-off assistance circuit 70.1 injects into the main circuit 34, through the cut-off switch 42.1, a counter-current in the opposite direction to the fault current, and intensity greater than the fault current, causing the current to pass through zero in the cut-off switch 42.1, which leads to the extinction of the electric arc. It is also noted that the cut-off module includes a surge protector 75.1 which is arranged electrically in parallel with capacitor 54.1 to limit the voltage across the terminals of capacitor 54.1.

Contrary to the basic architecture described in particular in the document K. TAKATA et. para. "HVDC Circuit Breakers for HVDC Grid Applications", Cl G RE AORC 2014, the breaking device 28 of FIG. 12A comprises a pre-charge circuit 50 which extends between the first primary point 44.1 and ground 52 and which comprises at least one pre-charge capacitor 54.1, at least one pre-charge resistor 56 and a pre-charge switch -load 58. As seen in the figure, in a C_C cutoff configuration, the cutoff device 28 is configured such that the pre-charge capacitor 54.1 of the pre-charge circuit 50 forms part of the circuit of cut-off assistance 70.1, in which it plays the role of the capacitor of the LC circuit intended to generate the oscillations. In the example, the pre-charge capacitor 54.1 is the only capacitor in the cut-off assistance circuit 70.1, in the sense that there is no capacitor in the section of the cut-off assistance circuit 70.1 which is distinct from the pre-charge circuit 50, here between the tapping point 76 and the secondary point 46.1. However, depending on the capacitive needs for on the one hand the precharge operation and on the other hand the cut-off assistance operation, it is possible to have, in addition to the precharge capacitor 54.1 which is arranged in the section of the pre-charge circuit 50 which is common with the cut-off assistance circuit 70.1, at least one other capacitor, this other capacitor being arranged in the section of the cut-off assistance circuit 70.1 which is separate from the pre-charge circuit 50, here between the tapping point 76 and the secondary point 46.1.

The pre-charge circuit 50 comprises a first section, which is common with the cut-off assistance circuit 70.1, which extends between the first primary point 44.1 and a tapping point 76 and which comprises the at least one pre-charge capacitor 54.1. The pre-charge circuit 50 comprises a second section, distinct from the cut-off assistance circuit 70.1, which extends between the tapping point 76 and the earth 52 and in which the pre-charge switch 58 is interposed. Note that the pre-charge resistor 56 of the pre-charge circuit 50 is, in this variant, arranged in the second section of the pre-charge circuit 50 which extends between the tapping point 76 and the ground 52 , therefore outside of the cut-off assistance circuit 70.1.

[0190] In the embodiment of FIG. 12A, the dedicated inductive component 90.1 of the cut-off assistance circuit 70.1 is arranged in the part of the cut-off assistance circuit 70.1 which is separate from the pre-charge circuit 50, here between the tapping point 76 and the secondary point 46.1.

The activation switch 72.1 is arranged in the section of the cut-off assistance circuit 70.1 which is separate from the pre-charge circuit 50, here between the tapping point 76 and the secondary point 46.1. This activation switch 72.1 is in its closed state in a C_C cut-off configuration of the cut-off device 28, during which the cut-off assistance circuit 70.1 is active to interrupt the flow of current in the switch cut-off 42.1 during opening. This activation switch 72.1 is open in the C_CH charging and C_PCH pre-charging configurations of the cut-off device 28, to prevent the electrical conductor 21, connected to the downstream point 38, cannot be discharged through the cut-off assistance circuit 70.1.

[0192] Illustrated in FIG. 12B a table which reads in the same way as that of FIG. 9B, in which there is represented, for each of the configurations described above, of a switching device 28 according to FIG. 12A, the state of the various switches in the configuration. In addition to the C_COND conduction, CJSOL isolation and C_C cutoff configurations, there is therefore a C_CH charging configuration in which the precharge switch 58 is in a closed state, so that the precharge capacitor 54.1, pre-charge resistor 56 and pre-charge switch 58 are all electrically in series in pre-charge circuit 50 between first primary point 44.1 and ground 52, while first primary point 44.1 is electrically isolated from the downstream point 38 of the cut-off device 28, in particular by the opening of the cut-off switch 42.1, but electrically connected to the upstream point 36, by the closing of the isolation switch 48 to allow the charging of the capacitor of pre -load 54.1. In this loading configuration C_CH, the activation switch 72.1 of the cut-off assistance circuit 70.1 is also open to isolate the tapping point 76 from the first secondary point 46.1 and therefore from the downstream point 38. There is also a pre-charge configuration C_PCH in which the pre-charge switch 58 is in its closed state so that the pre-charge capacitor 54.1, the pre-charge resistor 56 and the pre-charge switch 58 are all electrically in series in the pre-charge circuit 50 between the first primary point 44.1 and the ground 52, while the first primary point 44.1 is electrically isolated from the upstream point 36 of the cut-off device 28, by the opening of the isolation switch 48, but electrically connected to the downstream point 38, by the closing of the cut-off switch 42.1 to allow discharge of the pre-charge capacitor 54.1 in the conductor 21 of the electrical line av L. In this pre-charge configuration C_PCH, the activation switch 72.1 of the cut-off assistance circuit 70.1 is open to isolate the tapping point 76 from the first secondary point 46.1 and therefore from the downstream point 38. [0193] It is noted that, in the embodiment of FIG. 12A, when the cut-off switch 42.1 opens and the cut-off assistance is triggered, the capacitor 54.1 which is shared by the cut-off assistance circuit 70.1 and by the pre-charge circuit 50 unloads. Thus, when the current has been interrupted, the capacitor 54.1 can be discharged to a voltage different from that of the voltage source 17, or even lower than that of the voltage source 17. Also, in the context of a re-closing , it will be necessary, if one wants to carry out a pre-charging step of the electrical conductor 21, to first proceed to a step of recharging the capacitor 54.1 to recharge it, before being able to carry out the first pre-charging step. charged.

[0194] Illustrated in Figs. 13A to 17A different embodiments of a cut-off device which comprises several cut-off modules 40.1, 40.2, 40.3 which are interposed successively in the main circuit 34 between the first primary point 44.1 and the downstream point 38. In each of the modes of realization of Figs. 13A to 17A, the cut-off device 28 described can be used instead of those described above, with the same possible configurations, and with the same possible control mode during re-closing as described above, to implement a process for evaluating the integrity of an electrical conductor with at least one step of pre-charging the conductor during which an auxiliary auxiliary voltage source, distinct from the main voltage source 17, is connected to the electrical conductor 21 to turn it on while maintaining it isolated from the main voltage source 17 and from the rest of the electrical installation 10 as described above. These embodiments also make it possible to implement a step of recharging the pre-charge capacitor during which the cut-off device is brought into the charging configuration C_CH.

It is understood that the multiplication of cut-off devices arranged successively in the main circuit 34 makes it possible to reduce, at the time of opening, the voltage across the terminals of each of the cut-off modules. This makes it possible either to increase the breaking capacity of the breaking device 28, for a given performance of each module, or, to obtain a breaking capacity given the breaking device, to implement breaking modules having a significantly lower breaking capacity.

Thus, in each of these embodiments, the cut-off device 28 comprises, downstream of the first cut-off module 40.1 in the main circuit 34 of the cut-off device 28, at least one last cut-off module. A cut-off device comprising several cut-off modules could comprise only two cut-off modules, namely a first cut-off module and a last cut-off module interposed successively in the main circuit 34 between the first primary point 44.1 and the downstream point 38.

However, in the examples illustrated, the cut-off device 28 comprises more than two cut-off modules, namely, interposed successively in the main circuit 34 between the first primary point 44.1 and the downstream point 38, a first cut-off module , at least one additional cut-off module and a last cut-off module. Thus, in the examples illustrated, the cut-off device 28 comprises three cut-off modules, namely, interposed successively in the main circuit 34 between the first primary point 44.1 and the downstream point 38, a first cut-off module 40.1, a second module cutoff 40.2 forming an additional cutoff module, and a third cutoff module forming the last cutoff module. A cut-off device 28 according to the invention may comprise several additional cut-off modules interposed successively, in the main circuit 34, between the first cut-off module 40.1 and the last cut-off module 40.n.

The last cut-off module 40.3, here the third, comprises at least one cut-off switch 42.3, 60.3, 62.3 interposed in the main circuit 34 between a last primary point 44.3, downstream of the first secondary point 46.1, and a last secondary point 46.3 of the main circuit 34. Of course, the cut-off switch 42.3, 60.3, 62.3 of the last cut-off module 40.3 is capable of being controlled between an open state and a closed state to respectively determine an open state and a state closed of the last breaking module 40.3.

[0199] Between the first breaking module 40.1 and the last breaking module

40.3 in the main circuit of the breaking device 28, the breaking module additional also comprises at least one cut-off switch 42.2, 60.2, 62.2, interposed in the main circuit 34 between an additional primary point, here therefore the second primary point 44.2 downstream of the first secondary point 46.1, and an additional secondary point of the circuit main, here therefore the second secondary point 46.2 upstream of the last primary point 44.3. Of course, the cut-off switch 42.2, 60.2, 62.2 of the additional module 40.2 can be controlled between an open state and a closed state to respectively determine an open state and a closed state of the additional cut-off module.

[0200] In a breaking device comprising several breaking modules, there could be a pre-charging circuit which would be a dedicated circuit, as illustrated in FIG. 3, with a pre-charge circuit extending between the first primary point 44.1 and ground and comprising at least one pre-charge capacitor, at least one pre-charge resistor and a pre-charge switch.

[0201] However, in the case where at least one of the cut-off modules comprises a cut-off assistance circuit 70.1 implementing a capacitor, provision will preferably be made for at least one pre-charge capacitor of the circuit pre-charge 50 is also part of the cut-off assistance circuit of at least one of the cut-off modules. If several of the cut-off modules, or even all of them, each comprise a cut-off assistance circuit implementing a capacitor, provision will preferably be made for the pre-charge circuit 50 to comprise several pre-charge capacitors, and that at the at least one precharge capacitor of the precharge circuit is also part of the cut-off assistance circuit of a cut-off module while at least one other precharge capacitor of the precharge circuit is part of the cut-off assistance circuit of another cut-off module. For example, the pre-charge circuit 50 comprises several pre-charge capacitors, and each cut-off assistance circuit comprises at least one pre-charge capacitor of the pre-charge circuit. In other words, at least one of the cut-off assistance circuits, preferably several, more preferably all of the cut-off assistance circuits, comprising at least one capacitor which has a function in the cut-off assistance, shares this at least one capacitor with the pre-charge circuit 50. [0202] In the examples illustrated, the last cut-off module 40.3 comprises a cut-off assistance circuit 70.3 which extends electrically in derivation from the cut-off switch 42.3 of the last cut-off module 40.3 and from the main circuit 34 , between the last primary point 44.3 and the last secondary point 46.3 of the main circuit 34. part of the cut-off assistance circuit 70.3 of the last cut-off module 40.3. Similarly, in the examples illustrated, the additional cut-off module, for example the second additional cut-off module 40.2 comprises a cut-off assistance circuit 70.2 which extends electrically in derivation from the cut-off switch 42.2 of the additional cutoff 40.2 and of the main circuit 34, between the primary point 44.2 and the secondary point 46.2 of the main circuit 34 which are associated with this cutoff module, here the second 40.2. In a C_C cut-off configuration, the cut-off device 28 is configured such that at least one pre-charge capacitor 54.2 of the pre-charge circuit forms part of the cut-off assistance circuit 70.2 of the additional cut-off module, for example the second cut-off module 40.2.

[0203] Preferably, in the C_C cutoff configuration of the cutoff device, the cutoff assistance circuits of at least one upstream cutoff module, for example the first cutoff module 40.1, and of a downstream cutoff, for example the last cutoff module 40.3, are arranged electrically in series. In certain embodiments, this series connection is obtained by correctly configuring certain configuration switches 78.1 and/or isolation switches 77.1 and/or even shunt switches 79.1. In this context, it will be seen that, preferably, the cut-off assistance circuit of the downstream cut-off module, for example the cut-off assistance circuit 70.3 of the last cut-off module 40.3, comprises, successively and in this order from the primary point of this downstream module, for example the last primary point 44.3, at least one pre-charge capacitor 54.3 and an activation switch 72.3, with a tapping point 76 between the two in this power assistance circuit cut 70.3. Thus, the pre-charge circuit 50 comprises a first section which extends between the primary point of the upstream module, for example the first primary point 44.1, and the tapping point 76. This first section of the pre-charge circuit 50 is common with the cut-off assistance circuit, and comprises the at least one pre-charge capacitor of each of the cut-off assistance circuits modules whose assistance circuits are in series, for example those of the first cut-off module and of the last cut-off module. The pre-charging circuit comprises a second section, distinct from the cut-off assistance circuit, which extends between the tapping point 76 and the earth 52, and in which the pre-charging switch 58 is interposed.

[0204] It is therefore understood that, in a cut-off device 28 comprising several cut-off modules having a cut-off assistance circuit, it suffices that one of them has a tapping point from which the second section is detached of the pre-charge circuit, distinct from the cut-off assistance circuit, which extends between the tapping point 76 and the earth 52, and in which the pre-charge switch 58 is interposed. Indeed, in In this case, it suffices that, in the C_PCH pre-charging configuration and/or in the C_CH charging configuration, the cut-off assistance circuits of these modules, or at least the parts of these cut-off assistance circuits comprising the capacitor of these circuits, are placed in series to form the first section of the pre-charge circuit. This first section of the pre-charge circuit, which therefore includes capacitors also belonging to the cut-off assistance circuits, is connected, at the tapping point 76, with the second section of the pre-charge circuit, separate from the cut-off assistance circuit, which includes the pre-charge switch 58.

[0205] We will now detail how the general characteristics above are available in the different embodiments which are illustrated.

In the following description, it will be considered that, in each configuration of the cut-off device 28, all the cut-off modules 40.1, 40.2 and 40.3 which follow one another in the main circuit are in the same state at the same time, including as regards the state of the cut-off assistance circuits of each of the cut-off modules.

[0207] In the embodiment of FIG. 13A, all the cut-off modules 40.1, 40.2 and 40.3 are identical and similar to what has been described in relation to the embodiment of FIG. 9A. The different configurations of the cut-off device of FIG. 13A are deduced from the different states of the switches which are indicated in the table of FIG. 13B, which reads the same as that of Figure 9B.

[0208] In the embodiment of FIG. 13A, shunt switches 79.1, 79.2 have been shown which, for the usual configurations of conduction C_COND, of cutoff C_C, are in an open state. However, with precharge switch 58 in its open state, one could have shunt switches 79.1, 79.2 in their closed state for these configurations.

[0209] For each cut-off module 4O.i, a configuration switch 78.i (here 78.1, 78.2, 78.3) has also been shown in the cut-off assistance circuit 7O.i, between the switch of activation 72.i of the breaking module considered and the secondary point 46.i of the module considered. In each cut-off module 40.i, this configuration switch 78.i therefore has the same location as the counterpart in the embodiment of FIG. 9A.

It has also been shown that the last module 70.3, and each additional cut-off module, therefore here the second cut-off module 70.2, comprise an isolation switch 77.2, 77.3 in the cut-off assistance circuit considered, between the primary point 44.2, 44.3 of the cut-off module considered and respectively the capacitor 54.2, 54.3 of the cut-off assistance circuit of the cut-off module considered. Thus, the isolation switch 77.2, 77.3 and the configuration switch 78.2, 78.3 of a cut-off module considered delimit between them a segment of the cut-off assistance circuit which comprises the following elements of this circuit of cut-off assistance: the capacitor 54.2, 54.3, the activation switch 72.2, 72.3 and any tertiary surge protector 74.2, 74.3 which can be arranged across the terminals of the activation switch 72.2, 72.3. In the C_C breaking configuration, the isolating switch 77.2, 77.3 and the configuration switch 78.1 of a breaking module considered are in their closed state, so that the elements included in the segment can play their role of cutting assistance. It is further noted that, in the cut-off configuration C_C, the cut-off assistance circuits of at least the first cut-off module 40.1 and the last cut-off module 40.3, but preferably also those of the additional cut-off modules 40.2 are arranged electrically in series. For example, in the C_C cut-off configuration of the cut-off device 28, the cut-off assistance circuit 70.2 of the additional cut-off module 40.2 is arranged electrically in series between and with the cut-off assistance circuits 70.1, 70.3 of the first and last cutoff modules 40.1, 40.3.

However, in the cut-off configuration C_C, each cut-off assistance circuit, at least of the first cut-off module 40.1 and of the last cut-off module 40.3, but preferably also that or those of the cut-off module(s) additional 40.2 remains, considered individually, arranged in parallel with the cut-off switch 42.i of the cut-off module to which it belongs.

[0212] In the C_CH charging and C_PCH pre-charging configurations, the isolation switch 77.2, 77.3 and the configuration switch 78.1, 78.2,

78.3 of a cut-off module considered are in their open state, to isolate the elements included in the segment with respect to the main line 34. In addition, in the C_CH charging and C_PCH pre-charging configurations, the switch d activation 72.i is open and the shunt switches 79.1, 79.2 are closed. By this combination, we notice that, in the C_CH charging and C_PCH pre-charging configurations, the capacitors 54.1, 54.2 and

54.3 which, in the cut-off configuration C_C, are in the cut-off assistance circuit, then find themselves arranged directly in series with each other in the pre-charge circuit 50, between the first primary point 44.1 and earth. In this embodiment, and by this combination, only the capacitors 54.i of the cut-off assistance circuits are found in series in the pre-charge circuit. This series arrangement makes it possible to increase the voltage withstand of the assembly formed by these capacitors in the pre-charge circuit 50, which, in the C_C cut-off configuration, are each associated with a cut-off module. The presence of the shunt switches 79.1, 79.2, in their closed state, makes it possible to have, for the C_CH charging and C_PCH pre-charging configurations, the most direct possible path of the current in the pre-charging circuit 50.

[0213] On the other hand, it is understood that in this embodiment of FIG. 13A, for the C_PCH pre-charge configuration, the current generated by the discharge capacitors must pass through all cut-off switches that are in their closed state.

[0214] Also, it has been illustrated in FIG. 14A an embodiment in which all the switching modules 40.1, 40.2 and 40.3 are identical to each other, and are similar to what has been described in relation to the embodiment of FIG. 10A, the various configurations of the breaking device of FIG. 14A are deduced from the various states of the switches which are indicated in the table of FIG. 14B, which reads the same as that of Figure 10B.

The cut-off device 28 comprises, interposed successively in the main circuit 34 between the first primary point 44.1 and the downstream point 38, a first cut-off module 40.1, an additional cut-off module 40.2, also called here second cut-off module 40.2, and a last cut-off module 40.3. Each cut-off module 4O.i comprises a cut-off switch 42.i, here made in the form of two successive switches 6O.i, 62.i interposed in the main circuit 34 between a primary point 44.i and a secondary point 46 .i of the main circuit 34 which are associated with the cut-off module 4O.i. It is understood that each module is arranged in such a way that the primary point of an additional module or of the last module is directly connected, and preferably electrically merged, with the secondary point of the module which precedes it in the upstream-downstream direction in the main circuit 34.

[0216] Each cut-off module 4O.i includes a cut-off assistance circuit 7O.i implementing a capacitor, and it will be seen that the cut-off device 28 includes a pre-charge circuit 50 having at least as many pre-charge capacitors 54.i than the number of modules, and that each cut-off assistance circuit 7O.i comprises at least one pre-charge capacitor 54.i of the pre-charge circuit.

In the C_C cut-off configuration of the cut-off device, the cut-off assistance circuits 70.i are arranged electrically in series between the first primary point 44.1 and the last secondary point 46.3. This stems from the fact that each module is arranged in such a way that the primary point of an additional module or of the last module is directly connected, and preferably electrically coincident, with the secondary point of the module which precedes it in the upstream-downstream direction in the main circuit 34, and that the cut-off assistance circuit 70.i of each cut-off module extends electrically in derivation of the cut-off switch 42.i of the cut-off module 4O.i and of the main circuit 34, between the primary point 44.i and the secondary point 46.i of the main circuit 34 which are associated with this module.

Each cut-off assistance circuit 70.i comprises at least one capacitor, which can be seen to be advantageously a precharging capacitor 54.i in the sense that it also belongs to the precharging circuit 50 , and an activation switch 72.i.

The cut-off assistance circuit 70.3 of the last cut-off module 40.3 comprises, successively and in this order from the last primary point 44.3, at least one pre-charge capacitor 54.3 and an activation switch 72.3, with a tapping point 76 between the two in this last cut-off assistance circuit 70.3.

The pre-charge circuit 50 comprises a first section which extends between the first primary point 44.1 and the tapping point 76, which is common with the succession of series cut-off assistance circuits, and which comprises the at least one pre-charge capacitor of each of the cut-off assistance circuits of each of the cut-off modules. The pre-charge circuit 50 comprises a second section, distinct from the various cut-off assistance circuits, which extends between the tapping point 76 and the earth 52 and in which is interposed the pre-charge switch 58 .

In this embodiment, the breaking modules do not need to incorporate a configuration switch in each reference breaking assistance circuit as was provided in the embodiment of FIG. 10A.

[0222] Illustrated in FIG. 14A the presence of a bypass circuit 80 which extends, electrically parallel to the main circuit 34 between the first primary point 44.1 and a bypass point 82 arranged between the last secondary point 46.3 and the downstream point 38 In this bypass circuit 80 is interposed a bypass switch 84 which is in a closed state in the configuration of C_PCH pre-charge and in an open state in the C_CH charging, CJSOL isolation, C_C cut-off, and also in the C_COND conduction configurations. The bypass circuit 80 makes it possible to carry out, for the pre-charging configuration C_PCH, the pre-charging of the electrical conductor 21 of the downstream power transmission line, while maintaining cut-off assistance circuits 70. i with the lowest possible parasitic inductance. The presence of the bypass circuit 80 makes it possible to move the configuration switch 78 to place it in the main line 34 between the last secondary point 46.3 and the bypass point 82. The configuration switch 78 is closed in the conduction configuration C_COND, and in the cut-off configuration C_C of the cut-off device 28. The configuration switch 78 is open in the C_CH charging and C_PCH pre-charge configurations of the cut-off device 28, to prevent the conductor electric 21, connected to the downstream point 38, can not be discharged in particular through the cut-off assistance circuit 70.3. Preferably, configuration switch 78 is open in the CJSOL isolation configuration.

[0223] In the cut-off device 28 of FIG. 14A, only one cut-off module, the last one, has a tapping point 76 from which the second section of the pre-charge circuit is detached. In the C_PCH pre-charging configuration and/or in the C_CH charging configuration, all of each breaking module assistance circuit is placed in series to form the first section of the pre-charging circuit.

[0224] It is noted that it is possible to provide, before a first step of pre-charging the electrical conductor 21, a preparation step during which all current flow is cut in the cut-off assistance circuits 7O .i between the stitching point 76 and the last secondary point 46.3. This can be done for example by opening the configuration switch 78.

[0225] Illustrated in FIG. 15A an embodiment in which all the switching modules 40.1, 40.2 and 40.3 are identical to each other, and are similar to what has been described in relation to the embodiment of FIG. 11 A, with the difference that the configuration switch is no longer in the breaking modules, as has just been described with reference to FIG. 14A. The cut-off device 28 comprises, successively interposed in the main circuit 34 between the first primary point 44.1 and the downstream point 38, a first cut-off module 40.1, an additional cut-off module 40.2, also called here second cut-off module 40.2, and a last breaking module

40.3. Each cut-off module 4O.i comprises a cut-off switch 42.i interposed in the main circuit 34 between a primary point 44.i and a secondary point 46.i of the main circuit 34 which are associated with the cut-off module 4O.i. It is understood that each cutoff module 4O.i is arranged such that the primary point of an additional cutoff module or of the last cutoff module is directly connected, and preferably electrically merged, with the secondary point of the module which precedes in the upstream-downstream direction in the main circuit 34.

Each breaking module 4O.i comprises a breaking assistance circuit 7O.i implementing a capacitor, an inductor 9O.i and a controlled voltage source 92.i. The cut-off device 28 includes a pre-charge circuit 50 having at least as many pre-charge capacitors 54.i as the number of modules, and each cut-off assistance circuit 70.i includes at least one pre-charge capacitor 54.i charge of the pre-charge circuit.

[0228] In the embodiment of FIG. 15A, shunt switches 79.1, 79.2 have been shown which, for the usual configurations of conduction C_COND, cut-off C_C and insulation CJSOL, are in an open state. Thus, in the C_C cut-off configuration of the cut-off device, the cut-off assistance circuits 7O.i are arranged electrically in series, successively between the first primary point 44.1 and the last secondary point 46.3.

[0229] The cut-off assistance circuit 70.3 of the last cut-off module 40.3 comprises, successively and in this order from the last primary point

44.3, at least one pre-charge capacitor 54.3 and a controlled voltage source 92.3, with a tapping point 76 between the two in this last cut-off assistance circuit 70.3.

The pre-charge circuit 50 comprises a first section which extends between the first primary point 44.1 and the tapping point 76, which is common with the succession of series cut-off assistance circuits, and which includes the au at least one pre-charge capacitor of each of the cut-off assistance circuits of each of the cut-off modules. The pre-charge circuit 50 comprises a second section, distinct from the various cut-off assistance circuits, which extends between the tapping point 76 and the earth 52 and in which is interposed the pre-charge switch 58 In the example, the precharging resistor 56 is also in this second section which is distinct from the various cut-off assistance circuits.

It can advantageously be provided that, in the C_CH charging and C_PCH pre-charging configurations, the shunt switches 79.1, 79.2 are closed. Thus, the capacitors 54.1, 54.2 and 54.3 which, in the C_C cutoff configuration, are in the cutoff assistance circuit, are found, in the C_CH charging and C_PCH precharging configurations, then arranged directly in series l to each other in the pre-charge circuit 50, between the first primary point 44.1 and the ground 52. More specifically, in the C_PCH pre-charge configuration and/or in the C_CH charging configuration, only part of each cut-off module assistance circuit, comprising at least one capacitor 54.1 of the capacitance of each cut-off assistance circuit, is placed in series to form the first section of the pre-charge circuit. This series arrangement makes it possible to increase the voltage withstand of the assembly formed by the capacitors in the pre-charge circuit 50, which, in the C_C cut-off configuration, are each associated with a cut-off module. The presence of the shunt switches 79.1, 79.2, in their closed state, makes it possible to have, for the C_CH charging and C_PCH pre-charging configurations, the most direct possible path of the current in the pre-charging circuit. In particular, it is noted that the precharging circuit thus formed with the shunt switches 79.1, 79.2, in their closed state avoid the inductors 90.2 and 90.3 of at least some of the cut-off assistance circuits 70.2, 70.3.

In this embodiment, the 40.i breaking modules do not need to incorporate a configuration switch in each breaking assistance circuit. Indeed, it has been illustrated in FIG. 15A the presence of a bypass circuit 80 identical to that of the embodiment of FIG. 14A. The bypass circuit 80 extends electrically in parallel with the main circuit 34 between the first primary point 44.1 and a bypass point 82 arranged between the last secondary point 46.3 and the downstream point 38. In this bypass circuit 80 is interposed a bypass switch 84 which is in a closed state in the configuration C_PCH pre-charge and in an open state in the C_CH charging, CJSOL isolation, C_C cut-off, and also in the C_COND conduction configurations. The bypass circuit 80 makes it possible to carry out, for the pre-charging configuration C_PCH, the pre-charging of the electrical conductor 21 of the downstream power transmission line, while maintaining cut-off assistance circuits 70. i with the lowest possible inductance. The presence of the bypass circuit 80 makes it possible to move the configuration switch 78 to place it in the main line 34 between the last secondary point 46.3 and the bypass point 82. The configuration switch 78 is closed in the conduction configuration C_COND, and in the cut-off configuration C_C of the cut-off device 28. The configuration switch 78 is open in the C_CH charging and C_PCH pre-charge configurations of the cut-off device 28, to prevent the conductor electric 21, connected to the downstream point 38, can not be discharged in particular through the cut-off assistance circuit 70.3. Preferably, configuration switch 78 is open in the CJSOL isolation configuration.

[0233] The different configurations of the breaking device of FIG. 15A are deduced from the various states of the switches which are indicated in the table of FIG. 15B, which reads the same as that of Figure 9B.

[0234] Illustrated in FIG. 16A an embodiment comprising several successive cut-off modules in the main circuit, all the cut-off modules 40.1, 40.2 and 40.3 being identical to each other, and being similar to what has been described in relation to the embodiment of FIG. 11B, but the breaking modules being assembled in a manner analogous to what has been described in relation to FIG. 13A. Thus, in the C_C breaking configuration of the breaking device 28 of FIG. 16A, all of the 7O.i cut-off assistance circuits are electrically arranged in series by correctly configuring certain configuration 78.i, isolation 77.i and shunt 79.i switches.

There has thus been represented for each cut-off module 40.i, a configuration switch 78.i (here 78.1, 78.2, 78.3) in the circuit for assistance with cutoff 7O.i, between the controlled voltage source 921 of the cutoff module considered and the secondary point 46.i of the module considered. In each cut-off module 40.i, this configuration switch 78.ia therefore has the same location as the counterpart in the embodiment of FIG. 11 B.

There is also, for the last module 70.3, and for each additional cut-off module, therefore here for the second cut-off module 70.2, an isolation switch 77.2, 77.3 in the cut-off assistance circuit considered, between the primary point 44.2, 44.3 of the cut-off module considered and respectively the capacitor 54.2, 54.3 of the cut-off assistance circuit of the cut-off module considered. Thus, the isolating switch 77.2, 77.3 and the configuration switch 78.2, 78.3 of a cut-off module considered delimit between them a segment of the cut-off assistance circuit which comprises the following elements of this circuit of cut-off assistance: the capacitor 54.2, 54.3, the controlled voltage run 92i and the possible surge protector 75.2, 75.3 which can be arranged at the terminals of the capacitor

54.2, 54.3. In the C_C breaking configuration, the isolating switch 77.2, 77.3 and the configuration switch 78.i of a considered breaking module are in their closed state, so that the elements included in the segment can play their role. cutting assistance.

[0237] In this embodiment of FIG. 16A, shunt switches 79.1, 79.2 have been shown which, for the usual C_COND conduction, C_C cutoff and CJSOL insulation configurations, are in an open state and arranged such that, in the C_C cutoff configuration of the cut-off device, the cut-off assistance circuits 7O.i are, in their entirety, arranged electrically in series, successively between the first primary point 44.1 and the last secondary point 46.3. while remaining, considered individually, arranged in parallel with cut-off switch 42.i of the cut-off module to which they belong.

The cut-off assistance circuit 70.3 of the last cut-off module 40.3 comprises, successively and in this order from the last primary point

44.3, at least one pre-charge capacitor 54.3, a controlled voltage source 92.3, and a configuration switch 78.3, with a tapping point 76 between the two in this last cut-off assistance circuit 70.3. In the C_CH charging and C_PCH pre-charging configurations, the isolation switch n 77.2, 77.3 and the configuration switch 78.1, 78.2,

78.3 of a cut-off module considered are in their open state, to isolate the elements comprised in the segment with respect to the main line 34. In addition, in the C_CH charging and C_PCH pre-charging configurations, the shunt switches 79.1, 79.2 are closed. Thus, the capacitors 54.1, 54.2 and 54.3 which, in the cut-off configuration C_C, are each located in a cut-off assistance circuit 7O.i, are found, in the C_CH charging and C_PCH pre-charging configurations, arranged in series in the pre-charge circuit 50, between the first primary point 44.1 and the earth 52. The presence of the shunt switches, in their closed state, makes it possible to have, for the C_CH charging and pre-charge configurations C_PCH charge, a more direct current path in the pre-charge circuit, avoiding 90.2 inductors and

90.3 of the second and last breaking modules.

In the C_CH charging and C_PCH pre-charging configuration, the pre-charging circuit 50 comprises a first section which extends between the first primary point 44.1 and the tapping point 76, which comprises the at least one pre-charge capacitor of each of the cut-off assistance circuits of each of the cut-off modules. In this embodiment of FIG. 16A, it can be seen that, in the C_CH charging and C_PCH pre-charging configurations, the first section of the pre-charging circuit 50 also comprises the controlled voltage source 92.1 of each of the cut-off assistance circuits of each of the breaking modules. In doing so, the pre-charging step of the conductor 21 can be used to also charge capacitors in the controlled voltage source, which is then operational for a following cut-off step.

[0241] The pre-charge circuit 50 comprises a second section, distinct from the various cut-off assistance circuits, which extends between the tapping point 76 and the earth 52 and in which the pre-charge switch is interposed. -charge 58. In the example, the pre-charge resistor 56 is also in this second section which is separate from the various cut-off assistance circuits.

[0242] The different configurations of the breaking device of FIG. 16A are deduced from the different states of the switches which are indicated in the table of Fig. 16B, which reads the same as that of Figure 9B.

[0243] Illustrated in FIG. 17A an embodiment comprising several successive cut-off modules in the main circuit, all the cut-off modules 40.1, 40.2 and 40.3 being identical to each other, and being similar to what has been described in relation to the embodiment of FIG. 12A, but the breaking modules being assembled in a manner analogous to what has been described in relation to FIG. 14A.

The cut-off device 28 comprises, interposed successively in the main circuit 34 between the first primary point 44.1 and the downstream point 38, a first cut-off module 40.1, an additional cut-off module 40.2, also called here second cut-off module 40.2, and a last cut-off module 40.3. Each cut-off module 4O.i comprises a cut-off switch 42.i, interposed in the main circuit 34 between a primary point 44.i and a secondary point 46.i of the main circuit 34 which are associated with the cut-off module 4O.i . It is understood that each module is arranged in such a way that the primary point of an additional module or of the last module is directly connected, and preferably electrically merged, with the secondary point of the module which precedes it in the upstream-downstream direction in the main circuit 34.

Each breaking module 40.i comprises a breaking assistance circuit 70.1 implementing a capacitor 54.i and an inductance 90.i, and it will be seen that the breaking device 28 comprises a pre- load 50 having at least as many pre-charge capacitors 54.i as the number of modules, and that each cut-off assistance circuit 7O.i comprises at least one pre-charge capacitor 54.i of the pre-charge circuit -charged.

[0246] As in the embodiment of FIG. 14A, the cut-off assistance circuits are, in the cut-off configuration C_C of the cut-off device, arranged electrically in series, in their entirety, between the first primary point 44.1 and the last secondary point 46.3. Each assistance circuit comprises at least one pre-charge capacitor 54.i, which can be seen to be advantageously a pre-charge capacitor and in the sense that it also belongs to the pre-charge circuit 50, and a activation switch 72.i. In the example shown, each assistance circuit comprises an inductance 9O.i between the activation switch 72.i and the secondary point of the cut-off module 4O.i considered.

The pre-charge circuit 50 comprises a first section which extends between the first primary point 44.1 and the tapping point 41, which is common with the succession of series cut-off assistance circuits, and which comprises the at least one pre-charge capacitor of each of the cut-off assistance circuits of each of the cut-off modules. The pre-charge circuit 50 comprises a second section, distinct from the various cut-off assistance circuits, which extends between the tapping point 76 and the earth 52 and in which is interposed the pre-charge switch 58 .

In this embodiment, the breaking modules do not need to incorporate a configuration switch in each reference breaking assistance circuit as was provided in the embodiment of FIG. 10A. In fact, the presence of a bypass circuit 80 and of a configuration switch 78 in the main line 34 has been illustrated, for the description of which reference will be made to the passage above with reference to FIG. 14A.

[0250] Depending on the embodiments, it may be provided that, after the complete closing of the current cut-off device 28 by passing the current cut-off device to a conduction state, the discharge of the pre-capacitor(s) is caused. -charged. This could for example be implemented in particular within the framework of the embodiments of FIGS. 9A, 10A, 13A and 14A where the pre-charge capacitor must be discharged to ensure its role in the cut-off assistance function.

In the embodiments described above with reference to FIGS. 9A et seq., each of the cutoff modules of the embodiment considered comprises a capacitor which is implemented within the framework of the method of pre- charging of the electrical conductor of the power transmission line by being inserted, at least for the charging and pre-charging configurations, in the pre-charging circuit. However, the invention also covers the case of a breaking device which, in addition to a breaking module comprising a capacitance which is thus exploited, can comprise one or more additional switches in the main circuit 34 between the first primary point 44.1 and the downstream point 38, which are not associated with a capacity. Such switches may for example not include cut-off assistance circuits. Similarly, the invention also covers the case of a cut-off device which, in addition to a cut-off module comprising a capacitance which is thus exploited, may comprise one or more additional switches in the main circuit 34 between the first point primary 44.1 and the downstream point 38, which are associated with a capacitance, for example a capacitor, but whose capacitance is not inserted in the pre-charge circuit for the charge and pre-charge configurations. In both cases, such switches will preferably be controlled between their open and closed states, for each of the respective embodiments, in the same way as the cut-off switches as described with reference to FIGS. 9A et seq. It is thus noted that one or more such switches can be found in the main circuit 34 between the first primary point 44.1 and the downstream point 38, upstream of the first cut-off module 44.1, downstream of the last cut-off module 44.3, or between the first cut-off module 44.1 and the last cut-off module 44.3. Thus, in the context of the invention, it is appropriate to interpret the last breaking module as being the last breaking module associated with a capacitor which is inserted in the pre-charging circuit for the charging and pre-charging configurations. charged. Likewise, in the context of the invention, the first cut-off module should be interpreted as being the first cut-off module associated with a capacitor which is inserted in the pre-charging circuit for the charging and pre-charging configurations. -charged.

[0252] In general, each of the embodiments described above makes it possible to implement a control method to ensure the re-closure of the cut-off device by which the overhead line is supplied before reconnecting it to the network under high DC voltage by using the internal energy of the capacitor integrated in a switching device, in particular of mechanical type, without placing the line directly in electrical connection with the DC high voltage source 17, in order to limit the disturbances induced in the HVCD network unit 12, and more generally, in order to limit the disturbances imposed on the source of high direct voltage 17. The pre-charge of the line is carried out using an auxiliary circuit, referred to above as the pre-charge circuit. The solution enables multiple retries through controlled capacitor recharging and enables pre-charging of very long transmission lines.

Claims

[Claim 1] Switching device (28) for electric current under high direct voltage comprising:

- a main circuit (34), in which a nominal direct current flows in a conduction configuration (C_COND) of the breaking device, the main circuit extending between an upstream point (36) intended to be electrically connected to a source of direct high voltage (17) and a downstream point (38) intended to be electrically connected to a conductor (21) of a downstream electric line;

- at least a first cut-off module (40.1) comprising at least one cut-off switch (42.1) interposed in the main circuit between a first primary point (44.1) and a first secondary point (46.1) of the main circuit, the first primary point and the first secondary point being located in this order in the main circuit between the upstream point and the downstream point, and the cut-off switch being able to be controlled between an open state and a closed state to respectively determine an open state and a closed state of the first breaking module,

- an isolation switch (48), interposed in the main circuit between the upstream point and the first primary point, the isolation switch being capable of being controlled between an open state and a closed state; characterized in that the switching device (28) comprises a pre-charge circuit (50) which extends between the first primary point (44.1) and the ground (52) and which comprises at least one pre-charge capacitor (54, 54.1), at least one pre-charge resistor (56) and a pre-charge switch (58), in that the cut-off device has at least:

- a charging configuration (C_CH) in which the pre-charging switch (58) is in a closed state such that the pre-charging capacitor (54, 54.1), the pre-charging resistor (56) and the pre-charge switch (58) are all electrically in series in the pre-charge circuit load (50) between the first primary point (44.1) and the earth, while the first primary point (44.1) is electrically isolated from the downstream point (38) of the breaking device but electrically connected to the upstream point (36) to allow the charging the pre-charge capacitor;

- a pre-charge configuration (C_PCH) in which the pre-charge switch (58) is in its closed state such that the pre-charge capacitor (54, 54.1), the pre-charge resistor (56 ) and the pre-charge switch (58) are all electrically in series in the pre-charge circuit (50) between the first primary point (44.1) and ground (52), while the first primary point (44.1) is electrically isolated from the upstream point (36) of the cut-off device (28) but electrically connected to the downstream point (38) to allow discharge of the pre-charge capacitor (54, 54.1) in the conductor (21) of the downstream electric line ;

- an isolation configuration (C_ISOL) in which the first primary point (44.1) is isolated from the upstream point (36), with the isolation switch (48) in its open state, and is isolated from the downstream point (38 ), with the cut-off switch (42.1) in its open state, and in that, in the conduction configuration (C_COND), the pre-charge switch (58) is open to isolate the first primary point (44.1 ) with respect to the earth, and the upstream point (36) is electrically connected to the downstream point by the main circuit (34) comprising the cut-off switch (42.1) and the isolation switch (48) both in their closed state.

[Claim 2] Current cut-off device according to Claim 1, characterized in that the first cut-off module (40.1) comprises a cut-off assistance circuit (70.1) which extends electrically as a branch of the cutoff (42.1) and of the main circuit (34) between the first primary point (44.1) and the first secondary point (46.1) of the main circuit (34), and in that, in a cutoff configuration (C_C), the device circuit (28) is configured such that at least one pre-charge capacitor (54.1) of the pre-charge circuit (50) forms part of the cut-off assistance circuit (70.1) of the first cut-off module ( 40.1).

[Claim 3] Current cut-off device according to any one of Claims 1 or 2, characterized in that it comprises, downstream of the first cut-off module (40.1) in the main circuit (34) of the cut-off device ( 28), at least one last cut-off module (4O.n) comprising at least one cut-off switch (42.n) interposed in the main circuit (34) between a last primary point (44.n), downstream of the first secondary point (46.1), and a last secondary point (46.n) of the main circuit, and the cut-off switch (42.n) of the last cut-off module (4O.n) being capable of being controlled between a state open and a closed state to respectively determine an open state and a closed state of the last breaking module (4O.n).

[Claim 4] Current cut-off device according to Claim 3, characterized in that the last cut-off module (4O.n) comprises a cut-off assistance circuit (7O.n) which extends electrically in derivation from the cut-off switch (42.n) of the last cut-off module (4O.n) and of the main circuit, between the last primary point (44.n) and the last secondary point (46.n) of the main circuit, and in that, in a cut-off configuration (C_C), the cut-off device (28) is configured such that at least one pre-charge capacitor (54.n) of the pre-charge circuit (50) forms part of the cut-off assistance circuit (7O.n) of the last cut-off module (4O.n).

[Claim 5] Current interrupting device according to Claim 4, characterized in that the pre-charge circuit (50) comprises at least a first pre-charge capacitor (54.1) and at least a second pre-charge capacitor (54.n), and in that, in the cut-off configuration (C_C), the cut-off device is configured such that the first pre-charge capacitor (54.1) forms part of the cut-off assistance circuit ( 70.1) of the first cut-off module while the second pre-charge capacitor (54.n) forms part of the cut-off assistance circuit (7O.n) of the last cut-off module (4O.n).

[Claim 6] Current cut-off device according to any one of Claims 3 to 5, characterized in that it comprises, in the circuit main (34) of the cut-off device (28), between the first cut-off module (40.1) and the last cut-off module (40.3), at least one additional cut-off module (40.2) comprising at least one cut-off switch (42.2 ) interposed in the main circuit between an additional primary point (44.2), downstream of the first secondary point (46.1), and an additional secondary point (46.2) of the main circuit, upstream of the last primary point (44.3), and the cut-off switch (42.2) of the additional cut-off module (40.2) being capable of being controlled between an open state and a closed state to respectively determine an open state and a closed state of the additional cut-off module (40.2).

[Claim 7] Current cut-off device according to Claim 6, characterized in that an additional cut-off module (40.2) comprises a cut-off assistance circuit (70.2) which extends electrically in branch from the switch (42.2) of the additional breaking module (40.2) considered and of the main circuit (34) between the primary (44.2) and secondary (46.2) additional points of the main circuit which correspond to the additional breaking module (40.2) considered, and in that, in a cut-off configuration (C_C), the cut-off device (28) is configured such that at least one pre-charge capacitor (54.2) of the pre-charge circuit (50) forms part of the circuit cut-off assistance (70.2) of the additional cut-off module (40.2).

[Claim 8] Current cut-off device according to Claim 2, characterized in that the cut-off device comprises a single cut-off module (40.1) whose cut-off assistance circuit (70.1) comprises, successively and in this order from the first primary point (44.1), the at least one pre-charge capacitor (54.1) and an activation switch

(72.1), with a tapping point (76) between the two in the cut-off assistance circuit (70.1), in that the pre-charge circuit (50) comprises a first section, which is common with the cut-off assistance circuit (70.1), which extends between the first primary point (44.1) and the tapping point (76) and which comprises the at least one pre-charging capacitor

(54.1), and in that the pre-charge circuit (50) comprises a second section, distinct from the cut-off assistance circuit (70.1), which extends between the tapping point (76) and the earth (52) and in which the pre-charge switch (58) is interposed.

[Claim 9] Current cut-off device according to any one of Claims 1 to 7 taken in combination with Claims 2 and 4, characterized in that the cut-off device comprises at least one upstream cut-off module (40.1) and a downstream breaking module (40.3) whose breaking assistance circuits (70.1, 70.3) are, in the breaking configuration (C_C) of the breaking device (28), arranged electrically in series, in that the circuit of cut-off assistance (70.3) of the downstream cut-off module (40.3) comprises, successively and in this order from the downstream primary point (44.3), the at least one pre-charge capacitor (54.3) and a switch activation (72.3), with a tapping point between the two in the cut-off assistance circuit, in that the precharging circuit comprises a first section which extends between the upstream primary point (44.1) and the point of tapping (76), which is common with series cut-off assistance circuits, and which comprises the at least one pre-charging capacitor (54.1, 54.3) of each of the series cut-off assistance circuits, and in that the pre-charging circuit (50) comprises a second section, separate cut-off assistance circuit, which extends between the tapping point (76) and the earth (52) and in which the pre-charge switch (58) is interposed.

[Claim 10] Current cut-off device according to any one of the preceding claims, characterized in that it comprises a bypass circuit (80) which extends, electrically in parallel with the main circuit (34), between the first primary point (44.1) and a bypass point (82) arranged between the last secondary point (46.1, 46.n) and the downstream point (38), and in which is interposed a bypass switch ( 84) which is in a closed state in the pre-charge (C_PCH) configuration and in an open state in the charging (C_CH), isolation (C_ISOL) and cut-off (C_C) configurations.

[Claim 11] Current-breaking device according to Claim 10, characterized in that it comprises a configuration switch (78) which is arranged in the main circuit (34) between the last secondary point (46.1, 46.3) and the bypass point (82), and which is in an open state in the pre-charge (C_PCH) and charging (C_CH) configurations, and in a closed state in the conduction (C_COND) and cut-off ( CC).

[Claim 12] Current-breaking device according to any one of Claims 1 to 11 taken in combination with Claims 2 and 4, characterized in that it comprises at least one shunt switch (79.1, 79.2) which, in the charging configuration (C_CH) and in the pre-charging configuration (C_PCH), is in a closed state to connect in series, in the pre-charging circuit (50), the pre-charging capacitors

(54.1) belonging to the various cut-off modules (4O.i).

[Claim 13] Current cut-off device according to any one of the preceding claims, characterized in that the cut-off switch (42.i) of a cut-off module comprises a primary switch

(60.1), mechanical, and a secondary switch (62.i), mechanical, interposed successively in the main circuit (34) between the primary point

(44.1) and the secondary point (46.i) which correspond to the breaking module

(40.1) considered, but on either side of an intermediate point (64.i) of the main circuit (34) which corresponds to the cut-off module (4O.i) considered, the two mechanical switches (6O.i, 62.i) each being controlled between an open state and a closed state, and in that a cut-off module

(4O.i) comprises a primary surge protector (66.i) arranged in parallel with the primary switch (6O.i) between the primary point (44.i) and the intermediate point (64.i) which correspond to the module of cutoff (4O.i) considered, and a secondary surge protector (68.i) arranged electrically in parallel with the secondary switch (62.i) between the intermediate point (64.i) and the secondary point (46.i) which correspond to the cut-off module (4O.i) considered, and in that the cut-off assistance circuit (7O.i) of this cut-off module considered extends electrically in parallel with the assembly formed by the primary switch (6O.i) and the secondary switch (62.i) of this switching module considered, and electrically in parallel with the assembly formed by the primary surge protector (66.i) and the secondary surge protector (68.i) of this cut-off module (4O.i) considered.

[Claim 14] Current interrupting device according to any one of the preceding claims, characterized in that the downstream electric line comprises an overhead line, the conductor (21) of the downstream electric line being an overhead conductor.

[Claim 15] Electrical installation (10) comprising a DC high voltage source (17) electrically connected to at least one aerial conductor (21) of a downstream electric line comprising an aerial line, characterized in that it comprises, interposed between the DC high voltage source (17) and the overhead conductor of the downstream power line comprising an overhead line, a current interrupting device (28) according to any preceding claim, the DC high voltage source (17 ) being connected to the upstream point (36) of the cut-off device (28), and the aerial conductor (21) being electrically connected by an upstream end to the downstream point (38) of the cut-off device (28).

[Claim 16] Electrical installation according to claim 15, characterized in that it comprises, at a downstream end of the conductor (21) of the downstream electrical line, a current cut-off device.

[Claim 17] Method for controlling the closing of a current breaking device according to any one of claims 1 to 14, the breaking device (28) being initially in the isolation configuration (C_ISOL), characterized in that that it comprises at least one conductor precharging step during which the cut-off device (28) is brought into its precharging configuration (C_PCH) to energize a conductor (21) of a downstream electric line downstream of the downstream point (38); and in that the closing control method comprises, during or after the conductor pre-charging step, at least one parameter determination step (143) comprising the determination of at least one current or voltage parameter in the main circuit (34) or in the downstream electric line, and a decision step (144), during which it is decided, depending on the at least one parameter determined during the parameter determination step, whether or not to continue the complete closing (160) of the device of current breaking by switching from the current breaking device to the conduction configuration (C_COND).

[Claim 18] Control method according to Claim 17, characterized in that, to reach the conduction configuration (C_COND), the pre-charge switch (58) is open before the closing of the cut-off switch (42 .i) and the isolation switch (48).

[Claim 19] Control method according to any one of Claims 17 or 18, characterized in that, if the decision step (143) is not positive, the method continues, without going through the conduction configuration (C_COND) of the breaking device (28), by a recharging step (180) of the pre-charging capacitor (54.i) during which the breaking device (28) is brought into the charging configuration (C_CH ), then successively by a new pre-charging step (C_PCH) of the conductor (21), a new parameter determination step (143), and a new decision step (144), according to a precharging cycle.

[Claim 20] Control method according to Claim 19, characterized in that the step of recharging (180) the pre-charge capacitor (54.i) comprises:

- closing the isolation switch (48) and closing the pre-charge switch (58) to charge the pre-charge capacitor (54.i), maintaining the cut-off switch (42 .i) in its open state;

- after said closure of the pre-charge switch (58), the reopening of the isolation switch (48).

[Claim 21] Piloting method according to any one of Claims 19 or 20, characterized in that the number of cycles of pre- load for a given attempt to re-close the breaking device is limited.

[Claim 22] Control method according to any one of Claims 17 to 21, characterized in that, after at least one pre-charging step (141) of the conductor (21), the complete closing (160) of the power cut by passing the cut-off device (28) to its conduction configuration (C_COND) is continued if a voltage value in the main circuit (34), or in the downstream electrical line, exceeds a threshold value.

[Claim 23] Process for evaluating the integrity of an electrical conductor in an electrical power transmission line in an electrical installation comprising a main DC high voltage source electrically connected to an upstream end of the electrical conductor, with a device current cutoff upstream interposed between the main voltage source and the electrical conductor, and with a downstream end of the electrical conductor connected to a downstream electrical cutoff device, the evaluation process being of the type in which, in an initial state, the upstream breaking device and the downstream breaking device are respectively each in an insulation configuration C_ISOL so that, in the initial state, the electrical conductor is, except for an electrical fault affecting the electrical conductor, electrically isolated from the installation and the environment, characterized in that the evaluation process comprises at least one step of pre-charging of the conductor during which an auxiliary auxiliary voltage source, separate from the main voltage source, is connected to the conductor to energize the electrical conductor while maintaining the conductor isolated from the main voltage source and with respect to the rest of the electrical installation; and in that the evaluation process comprises, during or after the driver pre-charging step, at least one parameter determination step comprising the determination of at least one current parameter or voltage in the downstream electrical line, and an evaluation step during which the integrity of the electrical conductor is evaluated as a function of the at least one parameter determined during the parameter determination step. [Claim 24] Evaluation process according to Claim 23, characterized in that the evaluation process comprises or is followed by a decision step, during which it is decided, according to the at least one parameter determined during the parameter determination step, whether or not the complete closing of the current breaking device is continued by passing the current breaking device to a conduction configuration (C_COND).