EP1887667B2 - Ignition device with two electrodes for a spark gap and corresponding methods - Google Patents

Abstract

The component has two main electrodes (2, 3) arranged so as to form a spark-gap (4), and trigger elements (10, 11) distinct from the main electrodes. The trigger elements are arranged such that a disruptive discharge (12) appears between the trigger elements to cause a sparkover of an electric arc (6) between the electrodes. The trigger elements are formed by auxiliary electrodes (14, 15). The elements extend in an inter-electrode space (5) that separates the main electrode (2) from the main electrode (3). Independent claims are also included for the following: (1) a method for triggering an electric component (2) a method for manufacturing an electric component.

Description

The present invention relates to the general technical field of devices for protecting installations and electrical equipment against overvoltages, especially against transient overvoltages due to lightning.

The present invention more particularly relates to an electrical component comprising at least a first and a second main electrode forming a spark gap, as known from FR-A-2,880,468 and of CH 486 788 .

The present invention also relates to a device for protecting an electrical installation against overvoltages, said device being provided with a first and a second connection terminal intended to be connected to said electrical installation.

The present invention also relates to a method of triggering an electrical component comprising at least a first and a second main electrode forming a spark gap.

The present invention finally relates to a method of manufacturing an electrical component comprising a step of producing at least a first and a second main electrode forming a spark gap.

It is known to use protective devices of electrical installations in order to preserve them from overvoltages, in particular transient overvoltages caused by lightning atmospheric phenomena or by maneuvering incidents at the level of the networks.

These protection devices, generally designated by the term " surge arrester " or " surge protector " have the essential purpose of grounding fault currents and clipping the overvoltages to values compatible with the behavior of the installation electrical equipment and the equipment to which they are connected.

Known surge arresters may be based on different technologies depending on the nature of the protection component they implement.

In particular, spark gap arresters are known, that is to say using as protection component a device comprising two electrodes placed facing each other, one being electrically connected to the phase to be protected while the the other is electrically connected to the earth. Said electrodes are separated by an insulating zone, formed for example by a gas strip, such as air, or by a dielectric body.

When the voltage between the two electrodes reaches a predetermined level, there is a priming phenomenon leading to the establishment of an electric arc between said electrodes. Said electric arc creates a short circuit that allows the flow of the fault current to earth, which has the effect of protecting the equipment connected downstream of the surge arrester.

Although they provide some protection against lightning strikes, such lightning arresters nevertheless suffer from significant disadvantages related to their initiation.

Indeed, for an electric arc to form between said electrodes, it is necessary to apply between them a significant potential difference in order to create an electric field of sufficient intensity to cause the breakdown of the insulating zone, by example the ionization of the air space.

This ignition voltage, which depends in particular on the distance separating the two electrodes forming the spark gap, is particularly high, generally of the order of several kilovolts.

However, said triggering voltage directly conditions the protection level of the surge arrester. In fact, a spark gap arrester can only trip and discharge the fault current to ground when the overvoltage applied to its terminals exceeds the starting voltage. The existence of such a trip threshold has the consequence that the electrical installation to which the spark gap arrester is connected may be exposed, repeatedly, to overvoltages whose value lies between the nominal voltage of operation and the starting voltage.

In order to reduce the starting voltage of spark gap arresters, which in particular means reducing their response time with respect to transient overvoltages, it is known to provide these arresters with pre-triggering auxiliaries which favor the firing an arc when the spark gap is subjected to a surge.

In particular, it is known to interpose between the main electrodes of the spark gap an auxiliary electrode or " needle " in order to be able to cause a spark between said needle and one of the main electrodes by controlled application of a voltage pulse between said needle and said main electrode.

Experience shows that, for spark gap arresters of the prior art, the voltage necessary to create a certain spark between the needle and the main electrode is about 7 kilovolts if the distance between said needle and said main electrode is 2 millimeters. The time required to establish an electric arc between the two main electrodes is then of the order of 7 to 8 microseconds.

However, to show a spark between the needle and the main electrode, the arresters of the prior art generally use electronic trigger circuits, which often prove to be a weak point of said surge arresters, both technically and on the economic plan. Indeed, the known tripping circuits, which often use a large number of expensive components, are particularly sensitive to the stresses to which they are subjected during the operation of the arrester and age rapidly when they are stressed for the purpose of the flow of fault currents. This relative fragility of the trip circuit tends in practice to prematurely cause the failure of the arrester as a whole, even though the main protective spark gap is still functional.

In addition, despite the presence of an auxiliary electrode, the triggering time of the known spark gap arresters remains relatively high with respect to the characteristic durations of the transient disturbances, so that the level of protection conferred by them remains relatively poor.

This handicap generally results in a limitation of the use of spark gaps to " Type 1 " surge arresters, that is to say to primary arresters whose role is to limit, at the origin of the electrical installation, the currents resulting from direct lightning shocks (modeled by a 10/350 shock wave).

In particular, known spark gap arresters can generally not be used as " Type 2 " surge arresters, that is to say as secondary arresters that offer resistance to indirect lightning currents (modeled by a shock wave 8/20) whose role is to clip surges so that they are not dangerous for sensitive electrical equipment.

To achieve such secondary surge arresters, it is customary to favor varistor-type protection components, which are particularly expensive and less enduring than spark-gaps vis-à-vis the lightning strikes.

The objects assigned to the invention therefore aim to remedy the various disadvantages listed above and to propose a protection device comprising a new electric spark gap type component which has an improved priming capability.

Another object of the invention is to propose a new protection device comprising a spark gap-type electric component which is particularly simple, compact and has an optimized cost price.

Another object of the invention is to provide a new protection device comprising a spark gap type electric component which simplifies the installation and maintenance operations.

Another object of the invention is to propose a new device for protecting an electrical installation against overvoltages which confers an optimized level of protection to the installation to which it is connected.

Another object of the invention is to provide a new device for protecting an electrical installation against overvoltages that is simple in design and has an optimized cost.

Another object of the invention is to provide a new device for protecting an electrical installation against overvoltages which has an increased longevity.

The objects assigned to the invention are achieved by means of a protection device according to the first claim comprising an electrical component comprising at least a first and a second main electrode forming a spark gap, characterized in that it comprises at least a first trigger element and a second trigger element both separate from said first and second main electrodes, said first and second trigger elements being arranged such that a disruptive discharge can occur between them and the occurrence of said discharge disruptive can cause the initiation of an electric arc between the first and second main electrodes.

The objects assigned to the invention are also achieved by means of a device for protecting an electrical installation against overvoltages, said device being provided with a first and a second connection terminal intended to be connected to said electrical installation, characterized in that it comprises at least one electrical component according to the present invention, the first and the second main electrode of said electrical component being electrically connected to said electrical installation to be protected via said first and second connection terminals.

A method of triggering an electrical component comprising at least a first and a second main electrode forming a spark gap, characterized in that it comprises a step (a) during which there is shown a disruptive discharge between at least a first trigger element and a second trigger element both separate from said first and second main electrodes, so that the occurrence of said disruptive discharge can cause the initiation of an electric arc between the first and second main electrodes of said spark gap.

A method of manufacturing an electrical component comprising a step of producing at least a first and a second main electrode forming a spark gap, characterized in that it comprises a step (E ₁ ) during which one associates at least one first trigger element and a second trigger element both separate from said first and second main electrodes and a step (E ₂ ) in which said first and second trigger elements are arranged in such a way that a disruptive discharge may occur between them and the occurrence of said disruptive discharge may cause the initiation of an electric arc between the first and second main electrodes.

• La figure 1 illustre une représentation schématique d'un composant électrique de type éclateur conforme à l'invention.
• La figure 2 illustre un schéma électrique d'une première variante de réalisation d'un dispositif de protection contre les surtensions conforme à l'invention.
• La figure 3 illustre un schéma électrique d'une seconde variante de réalisation d'un dispositif de protection contre les surtensions conforme à l'invention.
• La figure 4 illustre un schéma électrique d'une troisième variante de réalisation d'un dispositif de protection contre les surtensions conforme à l'invention.
• La figure 5 illustre un schéma électrique d'une quatrième variante de réalisation d'un dispositif de protection contre les surtensions associant en série deux dispositifs conformes à l'invention analogues à ceux représentés sur la figure 3.

Other features and advantages of the invention will appear in more detail on reading the description which follows, and with the aid of the accompanying drawings provided for purely illustrative and non-limiting purposes, among which:

• The figure 1 illustrates a schematic representation of an electric spark gap type component according to the invention.
• The figure 2 illustrates a circuit diagram of a first embodiment of an overvoltage protection device according to the invention.
• The figure 3 illustrates a circuit diagram of a second variant embodiment of an overvoltage protection device according to the invention.
• The figure 4 illustrates a circuit diagram of a third variant embodiment of an overvoltage protection device according to the invention.
• The figure 5 illustrates a circuit diagram of a fourth variant embodiment of a surge protection device associating in series two devices according to the invention similar to those shown in FIG. figure 3 .

The electrical component 1 comprises at least a first main electrode 2 and a second main electrode 3, said main electrodes being arranged to form a spark gap 4.

Said first and second main electrodes, formed for example by metal strips, are separated by an inter-electrode space 5 formed of an insulating material, such as gas, in particular air, or a dielectric solid body.

Thus, when a sufficient voltage is applied between said first and second main electrodes 2, 3, an electric arc 6 is likely to be formed between them by breakdown of the insulator forming the inter-electrode gap 5.

According to an important characteristic of the invention, the electrical component 1 comprises at least a first trigger element 10 and a second trigger element 11, both of which are distinct from said first and second main electrodes 2, 3, and arranged in such a way that a disruptive discharge 12 may appear between them and the appearance of said disruptive discharge 12 may cause the initiation of an electric arc 6 between the first and second main electrodes 2, 3.

In a particularly advantageous manner, as will be explained in more detail in the following description, the use of a pair of trigger elements 10, 11 separate from the main electrodes 2, 3 facilitates the appearance of the arc. electrical 6 by accelerating the ionization of the inter-electrode space 5 and reducing the necessary starting voltage between the first and the second main electrode, compared to what would be observed in a spark gap comprising two main electrodes and a single trigger element. On the other hand, such an arrangement according to the invention is also likely to limit the intensity of the electric current flowing through the triggering elements 10, 11.

Preferably, the first trigger element 10 is formed by a first auxiliary electrode 14. Similarly, the second trigger element 11 is preferably formed by a second auxiliary electrode 15.

Preferably, the first and second triggering elements 10, 11 extend, at least in part, into the inter-electrode space 5 which separates the first main electrode 2 from the second main electrode 3.

Thus, if a potential difference is applied between the first and the second auxiliary electrode 14, 15, the electrical environment between said auxiliary electrodes 2, 3 can be modified, in particular by ionizing the corresponding part of the internal space. electrodes 5, and thus create, in the vicinity of the main electrodes 2, 3, conditions conducive to the initiation of an electric arc 6.

According to a preferred embodiment illustrated at figure 1 the first and second main electrodes 2, 3 delimit a flared, preferably substantially V-shaped, inter-electrode gap 5, said inter-electrode gap 5 extending between a narrow section 5A and a wide section 5B.

Thus, it will be possible to cause the blowing of the electric arc 6 formed at the narrow section 5A towards the wide section 5B, and consequently to promote the extinction of said arc 6.

This variant embodiment of the electrical component 1 according to the invention is therefore particularly suitable for the production of a device of the lightning arrestor type intended firstly to rapidly discharge the fault current caused by the arc 6 to the ground. by an overvoltage affecting an electrical installation to be protected and on the other hand to extinguish the electric arc just after the flow of said fault current to cut the current away and ensure continuity of service.

However, it is conceivable, without departing from the scope of the present invention, to use the electrical component 1 according to the invention for purposes other than that of overvoltage protection component.

As this is illustrated on the figure 1 the first and second trigger elements 10, 11 are preferably located at the narrow section 5A of the inter-electrode space 5.

In fact, the shorter the distance separating the main electrodes 2, 3, the lower the corresponding priming voltage. In other words, do the disruptive discharge 12 appears in the vicinity of said narrow section 5A, in particular at the base of the V formed by the main electrodes 2, 3 advantageously makes it possible to exploit the area of the spark gap 4 that is most favorable for the appearance of the electric arc 6.

Of course, the electrical component 1 according to the invention is in no way limited to a particular geometry of the main electrodes 2, 3, nor to any particular arrangement of the auxiliary electrodes 14, 15. In particular, the first and the second second trigger element 10, 11 can be recessed, flush or project into the inter-electrode space 5.

According to a preferred embodiment illustrated on the figure 1 , the assembly formed by the first and the second trigger element 10, 11 is substantially centered between the first and the second main electrode 2, 3. In other words, considering a substantially equidistant mean plane P of the two main electrodes 2, 3, the first and the second auxiliary electrode 14, 15 are preferably arranged substantially symmetrically with respect to said plane P.

In a particularly preferred manner, the main electrodes 2, 3 consist of substantially flat conductive strips arranged opposite one another so as to form a V whose sagittal plane also corresponds to the sagittal plane of the pair. of auxiliary electrodes 14, 15.

According to the invention, the smallest functional distance d ₁ which separates the first trigger element 10 from the second trigger element 11 is substantially smaller than the smallest functional distance d ₂ which separates the first main electrode 2 from the second main electrode 3 .

By " functional distance ", the distance separating two conductive portions belonging to two distinct conducting elements (first and second trigger elements for example) and between which a disruptive discharge (or an arc) is intended to be formed during operation is considered. normal component 1.

More specifically, as illustrated in the figure 1 the minimum functional distance d _{1 will} preferably correspond to the gap between the active tip 14A of the first auxiliary electrode 14 and the active tip 15A of the second auxiliary electrode 15, that is to say between the ends of said electrodes auxiliaries between which it is sought to show the disruptive discharge 12 (shown in dashed lines).

According to an alternative embodiment, the auxiliary electrodes 14, 15 may be coated or surrounded by an insulating sheath outside their active tips 14A, 15A which remain exposed, so that the disruptive discharge 12 can appear only in a predetermined functional zone, located substantially at said active points 14A, 15A.

According to another alternative embodiment (not shown), the auxiliary electrodes 14, 15 may be generally parallel and present locally a zone of approach, such as a constriction constituted by two conductive protuberances projecting towards each other from said auxiliary electrodes, so that the disruptive discharge 12 will appear preferentially at said approach zone.

Similarly, the functional distance separating the main electrodes 2, 3 in the variant embodiment shown in FIG. figure 1 will correspond to the spacing (variable) of the branches of the V, the minimum functional distance d ₂ being measured at the narrow section 5A of said V.

Thus, the voltage required to cause the occurrence of a disruptive discharge 12 between the first and the second trigger element 10, 11 distant from d ₁ is advantageously lower than that required for the initiation of an electric arc 6 between the main electrodes 2, 3 distant from d ₂ .

According to a preferred feature of the invention, the triggering elements 10, 11, and more particularly the active tips 14A, 15A of the auxiliary electrodes, are sufficiently distant from the main electrodes 2, 3 to avoid any parasitic electric arc formation, c that is, a short-circuit between a trigger element 10, 11 and a main electrode 2, 3, in the normal operation of the component 1. In other words, the preferential spatial arrangement of the elements 10, 11 and main electrodes 2, 3 prevents the main electric arc 6 " catches " one of the auxiliary electrodes 14, 15 and is established between a main electrode and an auxiliary electrode . Thus, in a particularly advantageous manner, the component 1 according to the invention makes it possible to dissociate substantially the control circuit, serving to stimulate the initiation by means of an ephemeral disruptive discharge, of the power circuit by which flow strong currents.

More generally, component 1 may advantageously make it possible to separate the tripping and flow functions by dedicating each to a separate circuit.

It is remarkable that within the meaning of the invention, the triggering elements 10, 11, and more particularly the auxiliary electrodes 14, 15, can then advantageously be designed to cause and support " only " a disruptive discharge 12 of moderate power and short duration (spark), while the main electrodes 2, 3 are designed to be able to discharge a high intensity electric current in the form of a relatively more durable electric arc 6, in particular caused by a transient surge due to lightning .

Preferably, the distance d ₁ is less than 30% of the distance d ₂ , and even more preferably between 10% and 20% of the distance d ₂ .

According to a particularly preferred embodiment variant, the minimum functional distance d ₁ separating the first trigger element 10 from the second trigger element 11, and more particularly the first auxiliary electrode 14 from the second auxiliary electrode 15, is between 0.4 mm and 1 mm, while the smallest functional distance d ₂ separating the main electrodes 2, 3 is about 3.5 mm.

Tests have shown that such an arrangement makes it possible to obtain, during the application of a transient overvoltage between the main electrodes 2, 3, an arcing time 6 (" response time "). of the order of 2 microseconds, which corresponds to a starting voltage of the order of 1.5 kV.

This represents a particularly appreciable gain compared to devices of the prior art in which the ignition is triggered by a disruptive discharge occurring between a single auxiliary electrode and one of the main electrodes of the spark gap. Indeed, under similar bias conditions, the establishment of an electric arc within said prior art devices requires 5 to 8 microseconds, depending on the distance between said auxiliary electrode and said main electrode, which corresponds to a starting voltage of between 2 kV and 4 kV.

An electrical component 1 can therefore advantageously be used for the production of Type 2 surge arresters. Indeed, since such a component allows the early initiation of an electric arc 6 between its main electrodes 2, 3 when it is subject to a surge caused by lightning, that is to say, it has a relatively low boot voltage, it offers a level of protection perfectly compatible with the holding of relatively sensitive electrical equipment.

According to a preferred embodiment, the main electrodes 2, 3 and the triggering elements 10, 11 are integrated in the same insulating casing having at least four electrical connection poles, for example pins projecting from a face of said casing, of which two are respectively connected to the first and second main electrodes 2, 3 and two are respectively connected to the first and second trigger elements 10, 11. The component 1 can therefore advantageously be in the form of a removable cartridge intended for example to be plugged onto a fixed base.

Such an arrangement confers an interchangeability component 1 and therefore facilitates its implementation or its replacement during installation or maintenance of the electrical equipment in which it is used.

In particular, the electrical component 1 may constitute an encapsulated spark gap closed at atmospheric pressure or a sealed spark gap GDT (Gas Discharge Tube).

It can also be associated with a breaking chamber 16 for splitting the electric arc 6 to facilitate its extinction after the disappearance of the overvoltage.

In the foregoing, a preferential geometry of spark gap 4 and trigger elements 10, 11 has mainly been described. However, the shape, the dimensions and the arrangement of electrical component 1, and in particular those of main electrodes 2 , 3 and release elements 10, 11, may be subject to modifications or adaptation without departing from the scope of the present invention.

The present invention also relates to the particular use of an electrical component 1 as described above within a protection device 20 of an electrical installation against overvoltages, especially against transient overvoltages due for example to lightning.

The term " electrical installation " refers to any type of device or network powered electrically and likely to experience voltage disturbances, including transient overvoltages due to lightning.

The protective device 20 according to the invention may therefore in particular constitute a surge arrester.

More particularly, the device 20 may advantageously constitute a Type 2 surge arrester in the sense of the IEC 61643-1 standard.

The use, by means of the present invention, of a spark gap 4 as a protection component in this type of arrester advantageously makes it possible to reconcile increased endurance and lower cost of the device 20 with respect to the Type 2 surge arresters of the prior art which resorts to varistors to form the power circuit.

The protection device 20 according to the invention is in particular intended to be connected bypass (" in parallel ") on the electrical installation to be protected, and more particularly to be arranged between a phase of the installation to be protected and the earth . It is also conceivable, without departing from the scope of the invention, that the device 1 is connected between the neutral and the earth, between the phase and the neutral, or between two phases to achieve a differential protection.

In order to allow the electrical connection of said device 20 to said electrical installation, it is provided with a first connection terminal 21 and a second connection terminal 22.

According to an important characteristic of the invention, the protective device 20 comprises at least one electrical component 1 according to the invention, the first and the second main electrode 2, 3 of said electrical component 1 being electrically connected to said electrical installation to be protected. via said connection terminals 21, 22.

According to an alternative embodiment not shown, one and / or the other of said connection terminals 21, 22 may be doubled to allow for example the simultaneous electrical connection to each of said terminals 21, 22 of two separate conductive elements, such as that cables, especially from the installation to be protected.

Of course, the electrical connection between a connection terminal 21, 22 and the corresponding main electrode 2, 3 may be direct or indirect. In particular, it is conceivable to associate other components in series with the electrical component 1 according to the invention.

Preferably, as illustrated in the Figures 2 and 3 , the protection device 20 comprises an activation means 23 connected to the first and second triggering elements 10, 11 for generating a disruptive discharge 12 between said first and second triggering elements 10, 11 so as to be able to cause the triggering an electric arc 6 between the first and second main electrodes 2, 3.

In a particularly preferred manner, said activation means 23 is sensitive to the voltage applied to the connection terminals 21, 22 of the device 20 and designed to generate a disruptive discharge 12 between the first and second triggering elements 10, 11 when said voltage passes a predetermined threshold.

Preferably, the activation means 23 is designed to create a potential difference between the first and the second trigger element 10, 11 and more particularly between the first and the second auxiliary electrode 14, 15.

For this purpose, the first or the second trigger element 10, 11 may be electrically connected to the secondary circuit of a transformer TX1 so that it is possible to vary the potential of said trigger element by circulating an electric current. in the primary circuit of said first transformer TX1.

According to a particularly preferred embodiment variant illustrated in FIG. figure 2 , the activation means 23 comprises an electronic circuit in parallel associating a gas spark gap 24 and a capacitor C ₁ so that, when said gas spark gap 24 is triggered, it bypasses said capacitor C ₁ which discharges into the primary circuit of the transformer TX1.

Of course, the protection device 20 according to the present invention is not limited to a particular embodiment of the activation means 23, other schemes that can be envisaged to generate an electric field, and in particular a voltage pulse, between the auxiliary electrodes 14, 15.

In a particularly advantageous manner, the protection device 20 according to the invention makes it possible to separate the control circuit comprising the activation means 23 and the trip elements 10, 11 of the power circuit formed by the main electrodes 2, 3.

This separation takes place first of all thanks to a constructive arrangement linked to a preferential spatial arrangement of the constituent elements of the device 20. In fact, the mutual proximity of the auxiliary electrodes 14, 15 and their arrangement with respect to the main electrodes 2, 3 makes it possible to confine substantially in a controlled space the disruptive discharge 12 which closes the control circuit 10, 11, 23, while maintaining an isolation distance between said control circuit 10, 11, 23 and the power circuit 2, 3 which is sufficient to substantially limit any risk of short circuit interference between them.

The separation can also be carried out or supplemented by separation means, for example electronic means, capable of limiting the intensity of the current flowing in the control circuit, and thus avoiding in particular that said control circuit does not spontaneously tend to short circuit all or part of the power circuit. For this purpose, as shown on the Figures 2, 3 and 4 it is preferable to interpose separating varistors V ₁ , V ₂ , V ₃ , V ₄ , V ₅ , V ₆ in series with the triggering elements 10, 11, respectively with the activation means 23, so as to that the latter are not directly electrically connected to the connection terminals 21, 22.

It will be noted in this respect that the variant embodiment of a protection device 20 illustrated in FIG. figure 3 does not differ from that illustrated in figure 2 by the arrangement of the varistors V ₁ , V ₂ , V ₄ which makes it possible to define the limits and the distribution of the electric current likely to flow in the first auxiliary electrode 14 and in the gas spark gap 24.

Moreover, it is particularly remarkable that the fact of accelerating the initiation of the electric arc 6 between the main electrodes 2, 3 by effectively and rapidly ionizing the inter-electrode space 5 thanks to the control circuit according to the The invention further contributes to " relieving " said control circuit in a very short time, by switching the electrical energy flow from said control circuit to the power circuit during the flow of fault currents.

Therefore, the control circuit 10, 11, 23 according to the invention is not stressed at each boot cycle of the spark gap 4, both in power and duration.

It is therefore advantageously possible to minimize its size by reducing the size of its various components, while preserving or even increasing its longevity compared to known devices.

According to an embodiment variant illustrated on the figure 4 and which can constitute an invention in its own right, the activation means 23 is formed by a first varistor V ₅ which preferably directly connects the first connection terminal 21 to the first trigger element 10 and a second varistor V ₆ which connects, preferably directly, the second connection terminal 22 to the second trigger element 11.

Such an activation means, unlike those capable of being implemented on the basis of the variants represented on the Figures 2 and 3 , does not have a TX1 voltage amplifier, and simply exploits the " natural " booting phenomenon that allows the occurrence of a disruptive discharge 12 between the auxiliary electrodes 14, 15 when an overvoltage is applied to the connection terminals 21, 22. However, the rapidity of appearance of said disruptive discharge 12 due to the proximity of said auxiliary electrodes, and the effectiveness of the ionization of the inter-electrode space 5 which results, gives this variant of the device 20 performance in terms of response time significantly greater than that of a spark gap 4 alone.

Advantageously, the first and the second varistor V ₅ , V ₆ simultaneously fulfill the roles of activation means 23 and separation means with respect to the power circuit.

The main advantage of such an alternative embodiment lies in the extreme simplification of the control circuit which considerably reduces both the size and the cost price of the device 20.

Finally, the protection device 20 according to the invention may comprise operating indicators 26, as well as safety fusible bridges 25 intended to open the power circuit and / or the control circuit in the event that it flows through a circuit. abnormally high current or abnormally high intensity, for example when the spark gap 4 reaches the end of its life under the effect of a conductive pollution.

Corresponding to the scheme of the figure 5 , the device 20 according to the invention comprises a first and a second branch 20A, 20B, each branch containing a component 1, 1 'as described above respectively associated with a corresponding activation means 23, 23'.

Said first and second branches 20A, 20B are preferably associated in series to connect together the connection terminals 21, 22 and thus form a power circuit comprising two successive spark gaps 4, 4 '.

For convenience of description, the elements of the second branch 20B repeat the references of their counterparts of the first branch 20A, with a symbol "'" (prime).

Preferably, the device 20 thus obtained corresponds to the " mirror " association of two identical " simple " devices, for example similar to that illustrated in FIG. figure 3 .

For this purpose, the gaps 4, 4 'can be electrically connected to each other by means of a " comb " 30 forming the midpoint of the power circuit.

Moreover, the common of the transformer TX1 of the activation circuit 23 of the first branch 20A will preferably be electrically connected to the second connection terminal 22 by a first connecting element 31, while the common of the transformer TX1 'of the circuit d activation 23 'of the second branch 20B will preferably be electrically connected to the first connection terminal 21 by a second connecting element 32.

It is in this respect remarkable that the respective activation means 23, 23 'are preferably arranged to cooperate in order to cause the simultaneous appearance, between the first and second triggering elements 10, 11, 10', 11 'of each two gaps 4, 4 ', a disruptive discharge 12, 12', so as to place substantially simultaneously said spark gaps in conditions conducive to their respective priming.

Thus, the assembly formed by the two branches 20A, 20B can advantageously switch quickly to its on state to discharge the fault current, the device 1 having more particularly a global response time, between the occurrence of a surge at its connection terminals 21, 22 and the flow of the fault current through the gaps 4, 4 'between said terminals 21, 22, substantially equal to the response time of a single branch considered separately.

In other words, the starting voltage of the assembly formed by the two branches 20A, 20B in series will be substantially equal to the ignition voltage of only one of said branches, and not randomly between the voltage of initiation of a branch and the sum of the respective starting voltages of each of the two branches.

Such an arrangement therefore makes it possible either to increase the nominal voltage (operating voltage) at the terminals 21, 22 of the device 20 without increasing the starting voltage of the latter or reducing its breaking capacity of the current (after the flow of the defect), or, conversely, to improve the breaking capacity of the device 20 for a given operating voltage.

The operation of an alternative embodiment of an overvoltage protection device will now be briefly described with reference to FIG. figure 2 .

When the device 20 is electrically connected to an electrical installation to be protected by means of its connection terminals 21, 22, the protection component 1 can be traversed by a discharge current.

As long as the voltage applied between the connection terminals 21, 22, which corresponds to the variant illustrated in FIG. figure 2 at the voltage between the first and the second main electrode 2, 3 does not substantially exceed the nominal operating voltage of the installation, the protection component 1, and more particularly the spark gap 4, is in its state blocker.

When an overvoltage appears at the connection terminals 21, 22, for example following a lightning strike, the voltage rise across the capacitor C ₁ causes the starting voltage of the spark gap 24 to be exceeded. By becoming on, the latter bypasses the capacitor C ₁ which discharges by creating a pulse of current through the primary circuit of the transformer TX1.

The transformer TX1 converts, and preferably amplifies, this current pulse into a voltage pulse applied to the second auxiliary electrode 15, so that a potential difference appears between the first and the second auxiliary electrode 14, 15.

The application of this potential difference, even if it may be moderate compared to that required for the direct priming of an electric arc between the main electrodes 2, 3, creates an intense electric field due to the proximity between the auxiliary electrodes 14, 15. This electric field generates a local ionization of the inter-electrode space 5, which is likely to lead to the appearance of a spark discharge 12, in the form of a spark, between said auxiliary electrodes 14 , 15.

In a particularly advantageous manner, the electrical power and more particularly the intensity of the current flowing through the trip elements 10, 11 during their activation remains moderate thanks to the separation varistors V ₁ , V ₂ , V ₃ . This avoids, in particular, the formation of a high-power arc between the auxiliary electrodes 14, 15, which would have the double negative consequence of disrupting the operation of the installation to be protected because of the difficulty it It would have to be extinguished because of the mutual proximity of said auxiliary electrodes 14, 15, and secondly to cause accelerated aging, or even destruction, of the control circuit.

This ionization of the inter-electrode space 5 facilitates the switching of the spark gap 4 in its conducting state. It indeed leads to the initiation of an electric arc 6 between the main electrodes 2, 3 for a priming voltage applied between said main electrodes 2, 3 much lower than that which would be necessary for the breakdown of the insulation filling the inter-electrode gap 5 in the absence of the trigger elements 10, 11 (or in the absence of activation thereof). Thus, the response time of the device 20 is considerably shortened.

It is remarkable that by centering the auxiliary electrodes 14, 15 between the main electrodes 2, 3, a substantially homogeneous ionization of the inter-electrode space 5 is obtained which makes it possible to optimize the initiation speed of the electric arc. 6, and to lower as much as possible the threshold that must be crossed voltage applied to the main electrodes 2, 3 to cause said priming.

When the arc 6 is initiated, the spark gap 4 is able to discharge the high intensity fault current caused by the overvoltage.

It is remarkable that in such an embodiment, the maintenance of the arc 6 after its initiation is independent of the activation of the first and second triggering elements 10, 11. Thus, after a small portion of the power conveyed by the overvoltage has been assigned to the triggering of the device 20, most of said power can be discharged freely through the power circuit formed by the main electrodes 2, 3 while the control circuit is deactivated.

As such, it is also remarkable that the control circuit according to the invention is solicited for a very short time due to the rapidity of the priming of the arc 6 and therefore the transfer of the energy flow of said control circuit to said power circuit.

As is well known to those skilled in the art, the electric arc 6 formed between the main electrodes 2, 3 tends to be blown towards the interrupting chamber 16 which facilitates its extinction after the flow of the fault current.

There is also described a method for tripping an electrical component 1 comprising at least a first and a second main electrode 2, 3 forming a spark gap 4.

Said triggering method comprises a step (a) in which a disruptive discharge 12 is shown between at least a first trigger element 10 and a second trigger element 11, both of which are distinct from said first and second main electrodes 2, 3 , the occurrence of said disruptive discharge 12 can cause the initiation of an electric arc between the first and second main electrodes 2, 3 of said spark gap 4.

Particularly preferably, step (a) comprises a substep (a ₁ ) during which a potential difference is applied between a first auxiliary electrode 14 and a second auxiliary electrode 15 which extend, at least in part, in the inter-electrode space 5 which separates the first main electrode 2 from the second main electrode 3.

Advantageously, said triggering method, when applied to an electrical component 1 within an overvoltage protection device 20 as described above, can constitute a method of protecting an electrical installation against overvoltages.

In this case, said method may comprise a step (b) in which the voltage applied to the connection terminals 21, 22 is evaluated and it is decided to implement step (a) if said voltage exceeds a value predetermined threshold. Advantageously, the steps (a) and (b) can be intimately linked by the use of an activation means 23 sensitive to the voltage applied to the connection terminals 21, 22, as described above, in order to stimulate the initiation of an electric arc 6 concomitantly with the appearance of an overvoltage audites terminals 21, 22.

There is described a method of manufacturing an electrical component 1 comprising a step of producing at least a first and a second main electrode 2, 3 forming a spark gap 4, said manufacturing method comprising a step (E ₁ ) during of which is associated with said spark gap 4 at least a first trigger element 10 and a second trigger element 11, both distinct from said first and second main electrodes 2, 3, and a step (E ₂ ) in which one arranging said first and second triggering elements 10, 11 such that a disruptive discharge can occur between them and that the occurrence of said disruptive discharge can cause the initiation of an electric arc 6 between the first and second main electrodes 2, 3.

Of course, the steps (E ₁ ) and (E ₂ ) can advantageously be simultaneous and merged.

According to an alternative embodiment of said manufacturing method, the step (E ₁ ) may comprise a substep during which the spark gap 4 formed by said first and second main electrodes 2 3 prefabricated subassembly comprising the first and the second triggering element 10, 11.

Advantageously, it will therefore be possible to apply the manufacturing method according to the invention to retrofit existing or installed spark gaps by providing the latter with a new trigger subassembly comprising for example two auxiliary electrodes 14, 15 held in a base insulating of appropriate dimensions, said base being connectable between the main electrodes 2, 3 of the existing spark gap.

In addition, the aforementioned manufacturing method can be implemented for the production of an overvoltage protection device 20 according to the invention, and constitute for example a lightning arrester manufacturing method.

Preferably, such a method of manufacturing an overvoltage protection device 20 further comprises a step (E ₃ ) in which the auxiliary electrodes 14, 15 are electrically connected to an activation means 23 as described. previously.

Thus, the electrical component 1 according to the invention advantageously makes it possible to provide particularly effective overvoltage protection devices which make it possible to reconcile the good resistance of spark gaps with respect to lightning currents with a low starting voltage.

Particularly advantageously, the excellent level of protection afforded by the electrical component according to the invention allows in particular its use in Type 2 surge arresters according to the IEC 61643-1 standard. Such surge arresters in accordance with the invention combine robustness and simplicity, and therefore have increased durability and reduced manufacturing cost, particularly with respect to prior art devices which employ varistors as protection components.

Claims (17)

1. A protection device (20) for an electrical installation against overvoltage, said device (20) being provided with a first and a second connection terminal (21, 22) intended to be connected to said electrical installation, the device comprising a first and a second branch (20A, 20B), each branch (20A, 20B) including an electrical component (1) comprising:

   - a first main electrode (2, 2') and a second main electrode (3, 3') forming a spark gap (4, 4'), the branches (20A, 20B) being associated in series for mutually connecting the connection terminals (21, 22) and forming a power circuit comprising, successively, the two spark gaps (4, 4'), the first and the second main electrodes (2, 3; 2', 3') of said electrical component (1) of each branch being electrically connected to said electrical installation to be protected, via said connection terminals (21, 22); and

   - at least a first tripping element (10, 10') and a second tripping element (11, 11'), both different from said first and second main electrodes (2, 3; 2', 3'), said first and second tripping elements (10, 11, 10', 11') being arranged so that a disruptive discharge (12) may appear between them and that the appearance of said disruptive discharge (12) may cause the ignition of an electric arc (6) between the first and second main electrodes (2, 3, 2' 3'),
   characterized in that the protection device includes means of activation (23, 23') arranged to cause the simultaneous appearance of a disruptive discharge between the first and second tripping elements (10, 11, 10', 11') respectively of the two spark gaps (4, 4'), and whereby the ignition voltage of the complete assembly formed by the two branches (20A, 20B) is substantially equal to the firing voltage of one of said branches alone.
2. The protection device according to claim 1, characterised in that, for at least one branch, the first and second tripping elements (10, 11) are formed by a first auxiliary electrode (14) and a second auxiliary electrode (15) respectively.
3. The protection device according to one of claims 1 or 2, characterised in that, for at least one branch, the first and second tripping element (10, 11) extend, at least partly, into the space between the electrodes (5), which separates the first main electrode (2) from the second main electrode (3).
4. The protection device according to claim 3, characterised in that, for at least one branch, the assembly formed by the first and the second tripping element (10, 11) is substantially centred between the first and second main electrode (2, 3).
5. The protection device according to one of the previous claims, characterised in that, for at least one branch, the smallest functional distance (d1) separating the first tripping element (10) from the second tripping element (11) is substantially smaller than the smallest functional distance (d2,) which separates the first main electrode (2) from the second main electrode (3).
6. The protection device according to claim 5, characterised in that, for at least one branch, the distance (d1) separating the first tripping element (10) from the second tripping element (11) is less than 30% of the distance (d2), which separates the first main electrode (2) from the second main electrode (3), and preferably is between 10% and 20% of this distance (d2).
7. The protection device according to one of the previous claims, characterised in that, for at least one branch, the minimum functional distance (d1) separating the first tripping element (10) from the second tripping element (11) is between 0.4 mm and 1 mm.
8. The protection device according to one of the previous claims, characterised in that the first and second main electrodes (2, 3) delimit a space between the electrodes (5), which opens out, preferably substantially in the shape of a V, said space between the electrodes (5) extending between a narrow section (5A) and a wide section (5B).
9. The protection device according to claim 8, characterised in that the first and second tripping element (10, 11) are located at the level of the narrow section (5A) of the space between the electrodes (5).
10. The protection device according to one of the previous claims, characterised in that, for at least one branch, the main electrodes (2, 3) and tripping elements (10, 11) are incorporated into a same insulating case with at least four poles for electrical connection, two of which are connected to the first and second main electrodes (2, 3) respectively and two of which are connected to the first and second tripping elements (10, 11) respectively.
11. Device according to one of claims 1 to 10, characterised in that the means of activation (23) are sensitive to the voltage applied to the terminals (21, 22) of said device (20) and designed to generate a disruptive discharge (12) between the first and second tripping elements (10, 11) of each branch when said voltage crosses a predetermined threshold.
12. Device according to one of claims 1 or 11, characterised in that, for at least one branch, the means of activation (23) are designed to create a difference in potential between the first and second tripping element (10, 11).
13. Device according to claim 12, characterised in that, for at least one branch, the first or second tripping element (10, 11) is electrically connected to the secondary circuit of a transformer (TX1), so that it is possible to make the potential of said tripping element (10, 11) vary by making an electric current circulate in the primary circuit of said transformer (TX1).
14. Device according to one of claims 1 to 13, characterised in that the means of activation (23) comprise an electronic circuit connecting in parallel a gas spark gap (24) and a capacitor (C1), so that, when said gas spark gap (24) is tripped, it short circuits said capacitor (C1), which is discharged into the primary circuit of the transformer (TX1).
15. Device according to one of claims 1 to 12, characterised in that the means of activation (23) are formed by a first varistor (V1, V4, V4', V5), which connect, preferably directly, the first connection terminal (21) to the first tripping element (10) of at least one branch, and a second varistor (V3, V3', V6), which connects, preferably directly, the second connection terminal (22) to the second tripping element (11) of at least one branch.
16. Device according to one of claims 1 to 15, characterised in that it constitutes a lightning arrester.
17. Device according to one of claims 1 to 16, characterised in that it constitutes a type 2 lightning arrester in the sense of standard IEC 61643-1.

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