FR2823002A1 - MULTIFUNCTIONAL SWITCH / DISCONNECTOR FOR ELECTRICAL DISTRIBUTION STATION - Google Patents

Abstract

The invention concerns a switch/disconnect (1) comprising for each phase at least three fixed connecting terminals (1A, 1B, 1C), capable of being switched into at least three switching positions including a closing position, an opening position and a grounding position. The closing position consists in electrically connecting a first input terminal (1A) to a second output terminal (1B), and the grounding position consists in electrically connecting the second terminal (1B) to a third terminal (1C) connected to the earth. The switch/disconnect further comprises four each phase a fourth connection terminal (1D) and a mobile contact (6) rotating about an axis (AX) for switching, said fourth terminal (1D) being designed to be connected to the second and third terminals (1B, 1C) via said mobile contact (6) when the switch/disconnect is switched in grounding position. The switch/disconnect is characterised in that the mobile contact (6) comprises two main ends one of which includes a connection element (6C) designed to be connected to said first terminal (1A) then to the second terminal (1B) when the switch is switched respectively from its closing position to its grounding position.

Description

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 Disclosed is a medium or high voltage switch / disconnector for electrical distribution station, with three switching positions including a grounding position and comprising a first input terminal, a second output terminal and a third terminal earthing, said terminals cooperating with a movable contact.

 An electrical distribution station typically comprises one or more incoming electrical cells which are each connected between a set of power bars and a distribution cable as well as one or more outgoing electrical cells, such as on a cable or on a protection cell of a transformer which is connected at the busbar input and at the output to a transformer, for example a medium voltage / low voltage transformer.

 A transformer protection cell includes a fuse circuit breaker which protects the upstream electrical circuit in the event of a fault on the transformer. This fuse circuit breaker is generally fitted with an interchangeable fuse after each melting. Changing a fuse in a transformer protection cell must be done, for personnel safety reasons, when the fuse circuit breaker is connected upstream and downstream to earth. European patent application EP-0924827 describes a transformer protection cell in which the earthing means upstream and downstream of the fuse circuit breaker comprise a head disconnector connected between a busbar and a switch, an upstream earthing switch which can bring the movable contact of the head disconnector to earth potential and a downstream earthing switch connected between earth and the cell output terminal. In this known protection cell, the switch is formed by a vacuum interrupter and a mechanical linkage linkage kinematically connects the two earthing switches and the head disconnector to simultaneously drive the earthing switches to the closed or closed position. opening during operation of the cell control mechanism according to a determined sequence The mechanical linkage linkage between the different disconnectors is a complicated arrangement which increases the size of the cell. Furthermore, a misalignment between the different rods of the control induces a risk of an electric arc appearing on the downstream earthing switch in the event of current return from the transformer.

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 An object of the invention is to provide a medium or high voltage switch / disconnector making it possible to carry out simple grounding upstream and downstream of a fuse circuit breaker in a protection cell of a transformer. Another object of the invention is to propose such a switch / disconnector which is of a compact design.

 To this end, the subject of the invention is a medium or high voltage switch / disconnector with three switching positions including a grounding position, comprising a first input terminal, a second output terminal and a third terminal. earthed, said terminals cooperate with a movable contact, characterized in that it further comprises a fourth terminal cooperating with the movable contact and in that the movable contact is shaped in such a way that in the positioning position earth of the switch / disconnector, the movable contact simultaneously connects the fourth terminal with said second and third terminals. The movable contact can for example form a fork with two teeth.

 In a protection cell of a transformer fitted with a switch / disconnector according to the invention, the fuse cut-out is connected upstream to the second output terminal of the switch / disconnector and downstream to the fourth terminal output of the switch / disconnector. In this way, when the switch / disconnector according to the invention is switched to its earthing position, an earthing upstream and downstream of the fuse circuit breaker is carried out by simple electrical connection without the need for no mechanical connection. Such an arrangement provides a transformer protection cell with better operating reliability and greater safety in use.

 According to the invention, the movable contact in the form of a two-pronged fork is a knife integral with a main rotary control shaft, this knife being able to be arranged with the four terminals of the switch / disconnector in a box of compact shape filled of a dielectric gas.

 The switch / disconnector according to the invention can be mounted in a flow cell or in a flow cell fitted to a public or private electrical distribution station. These cells can be produced in compact or modular form with gas insulation, for example a dielectric gas such as SF6.

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It is known to perform so-called cable test operations on the supply cells distribution cables in an electrical distribution station. These operations are so far quite complicated because they require disassembly and reassembly of the earthing circuit of the incoming cell. This problem can be solved more simply and with greater security using a switch / disconnector according to the invention comprising a third earthing terminal which is movable relative to the other terminals of the switch / disconnector in such a way that it can be disconnected from the moving contact or reconnected to the moving contact when the switch is switched to its earthing position. The third movable earthing terminal of the switch / disconnector according to the invention can for example be a pivoting finger secured to a secondary rotary control shaft extending parallel to the main control shaft of the switch / switch. With this arrangement, to carry out a cable test operation on a distribution cable of an inlet cell comprising the switch / disconnector according to the invention connected by its second output terminal to the distribution cable to be tested, the procedure is to as follows: the switch / disconnector is switched to its earthing position and a generator is connected to the fourth terminal of the switch / disconnector under earth protection; the third earthing terminal of the switch / disconnector is disconnected from the movable contact so that a voltage can be injected into the cable from the generator to carry out the test; at the end of the cable test operation, the third earthing terminal of the switch / disconnector is reconnected to the movable contact so that the generator can be disconnected from the fourth terminal of the switch / disconnector under protection of the earth.

 The switch / disconnector according to the invention is multifunctional. It makes it possible to carry out an upstream and downstream earthing in a starting cell of an electrical substation. It also makes it possible to carry out a cable test in an inlet cell of a substation.

 The invention is described in more detail below and illustrated in the drawings.

 Figures 1 to 3 are electrical diagrams of a protection cell of a transformer according to the invention.

 Figures 4 to 6 are electrical diagrams of an inlet cell according to the invention.

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Figures 7 to 10 show a first embodiment of the multifunctional switch / disconnector according to the invention.

 Figures 11 to 14 show a second embodiment of the multifunctional switch / disconnector according to the invention.

 As shown in Figures 1 to 3, a protection cell of a transformer 5 according to the invention comprises a multifunctional switch / disconnector 1 having a first input terminal 1A connected to a busbar 2, a second output terminal 1B connected upstream of a fuse circuit breaker 3. The fuse circuit breaker 3 is connected downstream to the transformer 5 through the output terminal 4 of the cell.

The switch / disconnector 1 comprises a third grounding terminal 1C connected to the ground and a fourth terminal 1D connected to the output terminal 4 of the cell by a flexible connection for example. The switch 1 finally comprises a movable contact 6 which is arranged to cooperate in a determined sequence with the four terminals 1A to 1D. According to the invention, this movable contact 6 is shaped to simultaneously connect three terminals of the switch. It is for example in the form of a two-pronged fork for simultaneously connecting the terminals 1B, 1C and 1D when the switch / disconnector 1 is switched to its earthing position.

 In FIG. 1, the switch / disconnector 1 is closed and the movable contact 6 connects only the terminals 1A and 1B so that the transformer 5 is supplied by the busbar 2.

 In FIG. 2, the switch / disconnector 1 is open and the movable contact 6 isolates between them the terminals 1A and 1B with a sufficient dielectric withstand isolation preventing any formation of an electric arc between them during application. standardized dielectric containers.

 In FIG. 3, the switch is switched to its earthing position according to which the movable contact 6 connects the terminals 1B, 1C and 1D at the same time. In this position of the switch / disconnector 1, the two terminals of the fuse 3 are brought to earth potential while the transformer 5 is electrically isolated from the busbar 2.

 Figures 4 to 6 show an incoming or outgoing electrical cell comprising a switch / disconnector 1 according to the invention having a third earthing terminal 1C which is movable relative to the other terminals 1A, 1 B, 1 D which allows a so-called cable test operation to be carried out. In this cell, the output terminal 4 of the

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cellule est raccordée en amont à la borne 1C de l'interrupteur/sectionneur et en aval à un câble de distribution 5'.

cubicle is connected upstream to terminal 1C of the switch / disconnector and downstream to a 5 'distribution cable.

 In FIG. 4, the switch / disconnector 1 is closed and the movable contact in the form of a fork with two teeth connects the terminals 1A and 1B so that the cable 5 is connected to the busbar 2.

l'interrupteur/sectionneur, les bornes 1B et 1D ainsi que la tête du câble 5'sont portées au potentiel de la terre. In FIG. 5, the switch / disconnector 1 is in its earthing position according to which the movable contact 6 simultaneously connects the terminals 1 B, 1 C and 1 D. In this position of

the switch / disconnector, terminals 1B and 1D and the head of cable 5 'are brought to ground potential.

 In FIG. 6, the third earthing terminal 1C has been moved and is disconnected from the movable contact 6 of the switch / disconnector.

 To test that the 5 'supply cable, which is generally a long underground cable, does not have a conduction defect, the procedure is as follows. When the switch 1 is switched to its earthing position as shown in FIG. 5, a generator GC is connected to the fourth terminal 1D of the switch / disconnector under earth protection. This generator GC is a generator for injecting an electrical voltage into the 5 'cable. To carry out the cable test operation, the third grounding terminal 1C is moved so as to disconnect it from the movable contact 6. A voltage can then be injected into the cable 5 'from the generator GC as illustrated in the figure 6. At the end of the cable test operation, the third earthing terminal 1C of the switch / disconnector is moved again to be reconnected to the movable contact 6 so that the generator GC can be disconnected from the terminal 1D under earth protection.

 Figures 7 to 10 show in a cross-sectional view a first embodiment of the multifunctional switch / disconnector 1. It comprises a cylindrical housing 7 of longitudinal axis AX closed to be filled with a dielectric gas. The housing 7 is here formed of two semi-cylindrical shells 7A, 7B produced for example, by molding an electrically insulating material such as an epoxy resin. The terminals 1A to 1D of the switch / disconnector 1 are arranged with the movable contact 6 inside the housing 7. The movable contact 6 is a substantially straight knife having one end provided with two teeth 6A, 6B. The knife 6

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 is fixed to a main rotary control shaft 8A which crosses the housing 7 along the longitudinal axis AX. As can be seen in FIGS. 7 to 10, the knife 6 is fixed at its central part on the shaft 8A while being offset from the latter. The control shaft 8A is made of an electrically insulating material. A polyphase switch / disconnector 1 may comprise several knives 6 fixed to the shaft 8A and arranged in the same cut-off volume inside the housing 7.

 Figure 7 shows the switch / disconnector 1 in the closed position. In this position of the switch / disconnector, the knife 6 extends vertically between the first input terminal 1A arranged in the upper part of the housing 7 and the second output terminal 1B disposed in the lower part of the housing 7. The two teeth 6A and 6B of the knife are arranged at the lower end of the knife 6, the tooth 6A connecting the terminal 1 B.

 The third earthing terminal 1C and the fourth terminal 1 D of the switch / disconnector are also arranged in the upper part of the housing 7, the earthing terminal 1C being disposed between terminal 1A and terminal 1D . The terminals 1A to 1D are distributed over the inner circular periphery of the housing 7 in the plane of rotation of the knife 6.

 The third earthing terminal 1C of the switch / disconnector is a finger secured to a secondary rotary control shaft 8B passing through the housing 7 parallel to the main control shaft 8A. The control shaft 8B is electrically conductive and several pivoting fingers such as 1C can be mounted on the secondary control shaft 8B by being arranged in the same cut-off volume inside the housing 7.

 The conductive terminals 1A, 1B and 1D distributed over the inner circular periphery of the housing 7 are arranged in bushings of the housing 7. Each of the different conductive terminals is dielectrically isolated from the others, so as not to generate ignition under normalized dielectric stress . For example, the dielectric strength between terminals 1A and 1C is reinforced by an insulating fin 9 extending vertically inside the housing 7 from its upper part to near the main control shaft 8A.

The main control shaft 8A also forms an insulating sheath 10 partially surrounding the knife 6 in order to reinforce the dielectric strength between the conductive parts inside the housing 7.

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In FIG. 8, the switch / disconnector 1 is switched, by a rotation of the main control shaft 8A, from its closed position to an open and isolated position of the terminals 1A and 18. In the figure 9, the switch / disconnector 1 is switched, by rotation of the main control shaft 8A, from its open position to a grounding position and the knife 6 simultaneously connects the terminals 1B, 1 C and 1D. More particularly, the tooth 6B of the knife 6 is connected to the terminal 1C and the tooth 6A of the knife 6 is connected to the terminal 1D. In FIG. 10, the earthing terminal 1C in the form of a pivoting finger is moved, by rotation of the secondary control shaft 8B, to be disconnected from the tooth 6B of the knife.

 If the switch / disconnector is used in a transformer fused circuit-breaker protection cell, it is not useful for the earthing terminal 1C to be left movable in the housing. It may be of fixed design in the housing. Alternatively, the blocking of the rotary movement of the earthing terminal 1C can be obtained simply by blocking the control acting on the secondary control shaft 8B.

 Figures 11 to 14 show in a cross-sectional view, a second embodiment of the multifunctional switch / disconnector 1. The switch / disconnector shown in Figures 11 to 14 differs from that shown in Figures 7 to 10 in that the movable contact 6 is a V-shaped knife and in this the terminals 1A and 1C are arranged in the upper part of the housing 7 while the terminals 1 B and 1 D are arranged in the lower part of the housing. Furthermore, the main control shaft 8A is disposed in the central part of the knife without being offset from the latter.

In FIG. 11, the switch / disconnector 1 is closed and the knife 6 connects only the terminals 1A and 1B. In FIG. 12, the switch / disconnector 1 is open. In Figure 13, the switch / disconnector is in a grounding position for terminals 1B and 1D. In this position of the switch / disconnector, the tooth 6A of the knife 6 is connected to the terminal 1D and the tooth 6B of the knife is connected to the terminal 1C. In FIG. 14, the switch / disconnector 1 is in a position for connection to the cable test generator, the earthing terminal 1C being disconnected from the knife 6. This earthing terminal 8 is still a pivoting finger in the housing 7 which is rotated by a secondary rotary control shaft 8B.

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 The switch / disconnector 1 according to the invention can be provided with one or more voltage sensors 12 each mounted to detect the presence of an electrical voltage on one of the terminals 1A, 1B or 1D of the switch / disconnector. The voltage sensor 12 can advantageously be a capacitive divider of annular shape which is placed around a crossing of one of the terminals 1A, 1B or 1D as illustrated in FIGS. 7 and 11.

 A feeder or protection cell of a transformer incorporating a multifunctional switch / disconnector 1 as described above can be part of a medium-voltage distribution station insulated in atmospheric air or gas at controlled pressure such as than SF6 or nitrogen. If it is an insulation with an insulating gas such as SF6, this requires a small volume. The construction of the switch / disconnector according to the invention is suitable for prefabricated distribution stations having a small volume.

Claims (9)

 1 / Medium or high voltage switch / disconnector (1) with three switching positions including a grounding position, comprising a first input terminal (1A), a second output terminal (1B) and a third terminal ( 1C) for earthing, said terminals cooperating with a movable contact (6), characterized in that it further comprises a fourth terminal (1D) cooperating with the movable contact and in that the movable contact is shaped in such a way so that in the earthing position of the switch / disconnector, the movable contact simultaneously connects the fourth terminal (1 D) with said second and third terminals (1 B, 1 C). 2 / switch / disconnector according to claim 1, wherein the movable contact (6) forms a fork with two teeth (6A, 6B). 3 / switch / disconnector according to claim 1 or 2, wherein the movable contact (6) is a knife secured to a main rotary drive shaft (8A) and wherein said terminals (1A-1 D) and the knife ( 6) are arranged in a housing (12) through which said main control shaft. 4 / switch / disconnector according to one of claims 1 to 3, wherein said third grounding terminal (1 C) is movable relative to the other terminals (1A, 1B, 1D) to be disconnected from the movable contact ( 6) or reconnected to the movable contact (6) when the switch / disconnector is switched to a grounding position.  5 / switch / disconnector according to claim 4, wherein said third grounding terminal (1C) is a pivoting finger secured to a secondary rotary control shaft (8B). 6 / Switch according to claims 3 and 5, wherein said main (8A) and secondary (8B) rotary control shafts are parallel to each other. <Desc / Clms Page number 10>  7 / switch / disconnector according to one of claims 1 to 6, comprising at least one voltage sensor (12) mounted to detect the presence of a voltage on one of said first, second or fourth terminal of the switch / switch. 8 / electrical cell comprising a switch / disconnector (1) according to one of claims 1 to 7 and a fuse circuit breaker (3) connected upstream to the second terminal (1B) of the switch / disconnector and downstream to the fourth terminal (1 D) of the switch / disconnector. 9 / Method for carrying out a cable test on a distribution cable (5 ') connected to the second output terminal (1B) of a switch / disconnector (1) according to claim 4 or 5, consisting of the following steps: l the switch / disconnector (1) is switched to its earthing position and a generator (GC) is connected to the fourth terminal (1D) of the switch / disconnector under earth protection; the third earthing terminal (1C) of the switch / disconnector is disconnected from the movable contact (6) so that a voltage can be injected into the cable (5 ') from the generator to carry out the test; at the end of the cable test operation, the third earthing terminal (1 C) of the switch / disconnector is reconnected to the movable contact (6) so that the generator (GC) can be disconnected from the fourth terminal (1D) of the switch / disconnector under earth protection.