FR2784246A1 - HIGH-VOLTAGE MULTI-FUNCTIONAL MONOBLOCK ELECTRICAL LINK, COMPRISING A FLEXIBLE THROUGHPUT AND WIRE - Google Patents

Abstract

A high voltage electrical link 20 intended for the connection of the power circuit of an electrical apparatus 4 confined in a tank 9 containing a fluid dielectric 16, comprises a feed-through 23 extending outside the tank 9 by a flexible electric wire 22. This compact connection makes it easier to connect the equipment 4. Preferably, the end of the connection inside the tank has a connection 23, which can be a specific connection for plugging in a fuse. 10 integrated into the bushing 23, which reduces the risk of electrical faults in the tank 9 upstream of the fuse 10.

Description

AT

  MULTIFUNCTIONAL HIGH VOLTAGE ELECTRICAL LINK

  MONOBLOCK, COMPRISING A CROSSING AND AN ELECTRIC WIRE

FLEXIBLE

  The invention relates to an electrical connection intended for the transport of electrical energy between a high-voltage switchgear disposed inside a protective tank containing a

  liquid or gaseous dielectric, and an electrical installation outside the tank.

  Commonly, some high voltage electrical equipment is confined in grounded metal tanks and constituting sealed or almost leaktight enclosures filled

  a dielectric fluid, generally oil or a gas such as sulfur hexafluoride.

  The connections of such equipment with the external network are made through high-voltage bushings comprising a rigid conductive core, one end of which is placed inside the tank and the other outside of the tank, this core being wrapped in a molded polymer ensuring electrical insulation and fixing to the tank cover. To connect the switchgear to the network, it is necessary to fix an electric cable on the bushing. The more intense the currents that must flow in the crossing, the more delicate the operation, because the size of the high voltage cables used makes them not very flexible. Constraints

  Mechanics at the crossing are important and can lead to failures.

  In addition, the number of connection interfaces resulting from such an architecture is large, which results in additional cost, excessive bulk and risks of additional failure. An objective of the present invention is to provide an electrical connection reducing the risk of failure at the interface between the bushing and the external connection cable. Another objective is to reduce the number of connection interfaces in a high voltage installation comprising an apparatus confined in a tank. Another objective is to facilitate the electrical connection of a high voltage switchgear confined in a tank. Another objective is to reduce the overall size of an electrical connection device

  a high voltage switchgear confined in a tank.

  These objectives are achieved by means of a one-piece high-voltage electrical connection intended for the transport of electrical energy between an electrical apparatus placed inside a confinement tank containing a liquid or gaseous dielectric and comprising an orifice, and an electrical installation. external to the tank, the connection comprising: At an internal end intended to be disposed inside the tank; * an outer end intended to be disposed outside the tank; * an electrically conductive core extending between the two ends;

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  an electrically insulating envelope enveloping the core and comprising a bushing capable of being inserted into the orifice and of electrically insulating the core from the wall of the tank, this bushing comprising means for closing the orifice and for fixing to the wall of the tank, able to cooperate with complementary fixing means so as to establish the seal between the inside and the outside of the tank at the orifice; connection further comprising, between its outer end and the crossing, a flexible electric wire comprising a deformable metallic conductor constituting a part of the core of the connection and a tubular insulating sheath made of elastomeric material constituting a part

  of the insulating envelope of the connection and enveloping the deformable conductor.

  This link constitutes a multifunctional device making it possible to group together two usually distinct elements, namely an insulated cable and a crossing, and thus to eliminate the

  expensive and bulky connection device usually connecting the cable to the bushing.

  Advantageously, the dimensional and mechanical characteristics of the flexible electric wire are such that it is capable of bending in at least one reference plane of at least 90 on either side of a median reference position. Such flexibility is obtained, for example, by reducing the section of the individual metallic wires of the core, and / or by choosing a braiding or stranding mode allowing great flexibility of the core, and / or by using an elastomeric material. of great elasticity. This flexibility gives

  mounting a great freedom of positioning of the tank in relation to its environment.

  Naturally, it is even more advantageous to allow a bending of the order of 180.

  Preferably, the insulating sheath of the flexible electric wire is molded on the part of the core which it envelops. Molding makes it possible, better than extrusion, to control the interface between the deformable conductor and the sheath. Indeed, it is essential to limit the presence of bubbles in the sheath as much as possible, because these defects, in the presence of high electric fields, on the one hand generate a phenomenon of partial discharges detrimental to the durability of good insulation, and on the other hand constitute areas of weakness due to the reduction of

the thickness of the insulating medium.

  Preferably, the part of the core included in the flexible electric wire comprises a braid made up of several strands of metallic wire intertwined or crossed relatively flat in the manner of a mat, which gives the electric wire much greater flexibility than that single-wire or stranded cables of equivalent linear resistance. For less currents

  strands, stranded or single wire may offer an alternative.

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  Preferably, the part of the core included in the flexible electric wire comprises an elastomer coating loaded with conductive particles, coating the deformable conductor or conductors. The interface between metal and elastomer is thus made on a thickness of elastomer brought to the potential of the metal. This arrangement eliminates the drawback of bubbles or detachment from the surface of the metal since these singularities are found in a medium of constant potential. In addition, the coating layer makes it possible to eliminate the effects of points of the strands projecting radially from the metal part of the core, which is particularly useful when the latter consists of a braid. Indeed, it is in practice difficult to give a metallic braid a regular external surface. Some strands

  metal therefore risk entering the elastomeric material of the insulating jacket.

  Such a singularity induces in its vicinity a very high gradient of the electric field, thus constituting a zone of weakness, where the phenomena of aging under dielectric stress will be accelerated until rapidly producing a breakdown of the insulator. In response to this problem, the conductive coating makes it possible to smooth the equipotentials of the electric field in the vicinity of the irregularities of the surface of the braid. In practice, the coating

  conductor can be made of a silicone substrate loaded with conductive carbon black.

  Advantageously, the connection comprises an outer shield, comprising at least one film comprising an elastomer loaded with conductive particles or a tubular braid or a sheath overmolded with elastomer loaded with conductive particles or a combination of the above. The shielding firstly ensures the regularity of the equipotential surfaces, and therefore that of the electric field existing in the insulating material confined between the core and the shielding. Vis-à-vis the external environment, it also allows control of the field, the value of which becomes negligible. It is also possible to ensure that the shielding also makes it possible to drain the earth fault currents. Depending on the applications, the surface conductance of the necessary shielding is then chosen according to the geometry of the device and the level of leakage current expected, itself depending on the type of distribution network and

including the neutral regime.

  Preferably, at least one of the ends of the link, or both, have a connection interface. This arrangement increases the multifunctional nature of the link. Advantageously, the connection interface comprises an insulating envelope in the same elastomeric material as the envelope coating the core, which makes it possible to carry out the

  molding of the electrical wire of the connection interface simultaneously or sequentially.

  According to a particular embodiment, the connection interface constitutes the end of the connection intended to be inside the tank and comprises a sheath for connection of a terminal of a fuse, capable of elastically deforming from so as to wrap around the fuse terminal and to ensure sealing and electrical insulation between the fuse terminal and the interior of the tank. This arrangement allows great control over the quality of the electrical insulation in the part of the circuit located directly upstream of the fuse, and in particular the part internal to the tank located between the bushing and the fuse. This arrangement greatly reduces the risk of an electric arc striking in the tank upstream of the fuse,

  especially in the event of a decrease in the level or quality of the dielectric in the tank.

  Advantageously, the envelope is made of an elastomeric material molded on the core. There is then perfect continuity of the insulation between the two ends of the connection. This

  provision further makes possible, if necessary, a molding in a single injection.

  Alternatively, it may be preferable to provide different elastomers for different parts of the envelope or to use another type of insulating material for a part at

  less of the envelope, especially for the crossing.

  Other advantages and characteristics of the invention will emerge from the description which follows

  follow different embodiments of the invention, given by way of nonlimiting examples and represented in the appended drawings in which: * FIG. 1 represents a sectional view of a medium voltage electrical apparatus supplied by means of an electrical connection according to a first embodiment of the invention; * Figure 2 shows a longitudinal sectional view of an electrical connection according to the first embodiment of the invention, in a reference position; * Figure 3 shows a longitudinal sectional view of a second embodiment

of the invention.

  With reference to FIG. 1, a medium-voltage electrical panel 1, confined in an enclosure 2 filled with a gaseous dielectric, in this case sulfur hexafluoride, comprises

  feeders 3 delivering current from the network to electrical equipment 4 constituting a load.

  This apparatus 4 comprises a three-phase medium / low voltage transformer 5, and a protection device comprising a three-phase circuit breaker 6 and fuses 10, connected upstream of the primary windings of the transformer 5. The circuit breaker 6 is intended for protection against faults electrics inducing only low overcurrents at the primary level, in particular faults appearing on the secondary windings. Each fuse 10 is connected in series between the network and the circuit breaker, and selectively sensitive

  to short circuits affecting the primary windings of transformer 5. A description

  Detailed information on this device can be found in the French patent application bearing the national registration number 98/10519. Each fuse 10 comprises, conventionally, two metal end terminals 11, 12 connected by a fuse element 13 contained in a cylindrical body 14 comprising a solid dielectric material. The electrical equipment 4 is confined in a tank 9 making up a sealed enclosure filled with a dielectric fluid 16,

in this case oil.

  An electrical connection 20 according to the first embodiment of the invention, represented in FIGS. 1 and 2, is intended for the electrical supply of the primary windings of the transformer and connected on the one hand to the network at the level of the feeders 3, and on the other hand to the switchgear 4. This electrical connection comprises an external connection 21 intended for connection with the network, a central part constituting a flexible electric wire 22, a bushing 23 ensuring the sealing at the level of an orifice practiced in a wall of the tank 9,

  and an internal connection 24, into which the terminal 11 of the fuse 10 is connected.

  The electrical connection 20 comprises an electrically conductive core 25, covered by an envelope 26 made of a good insulating elastomeric material. The core 25 has in its middle part a braid 27 made up of metal strands and, at each end, a pin 28, 29 crimped onto the braid 27. the core 25 further comprises a conductive coating 30 coating the metal braid 27. The coating layer 30 makes it possible to eliminate the effects of the tips of the strands projecting radially from the braid 27 and to smooth the equipotential surfaces in the vicinity of the irregularities of the surface of the braid. In practice, the conductive coating 30

  consists of a silicone substrate loaded with conductive carbon particles.

  The casing 26 is, in this embodiment, constituted by a cold vulcanizable silicone of generally cylindrical shape, which also constitutes the body of the bushing and of the connections on the network side and on the load side. The envelope 26 is covered with a shield consisting of a conductive film 31 which is brought to ground potential. As an indication, for a nominal voltage of 24 kV and a nominal current of 100 A, the diameter of the braid is around 8 mm, for an outside diameter of the cable around 30 mm. As can be seen in the rest positions of Figure 2 and in service of Figure 1, the cable of the link 20 is capable of bending by a large angle, in this case at least 180. In other words, when one end of the link is fixed, for example the inner end, the other is capable of reversibly passing from a first reference position - for example the position of rest of Figure 2 - in a second position in which it has undergone a rotation of 180 - in the example, the position of Figure 1. In this case this bending is possible in all planes of space, on either side of the rest position. These degrees

  of freedom allow the free end of the connection to be positioned without excessive stress.

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  The bushing 23 and the internal connection 24 are, in this embodiment, nested one inside the other. The bushing 23 includes a fixing flange 32 which is fixed to the wall of the tank 9 by means of fixing screws 33. A protective cover 41 protects a current transformer 42 delivering a signal representative of the current intensity crossing the connection 20. The internal connection 24 comprises a sheath 34, a part of which is shaped as a cup taking approximately the shapes of the terminal of the fuse on the network side, with a cylindrical wall and a flat bottom on which the end of the side pin is flush load 29 of the conductive core of the connection 20. This cup 35 is extended into a cylindrical lip 36 of slightly smaller diameter so as to conform to the body 14 of the fuse. The internal walls of the cup 35 are covered with a film

  conductor, so that they are at the potential of the load side pin 29 of the core.

  When the fuse 10 is inserted in the connection 24, the peripheral lip 36 of the connection cooperates with the cylindrical body 14 of the fuse and undergoes an elastic deformation which makes it possible to ensure a sufficient contact pressure with the body of the fuse, so that a tight seal is formed between the inside of the cup 35 and the outside environment

  immersed in the fluid dielectric of the tank 9.

  The external connection 21 comprises a cup-shaped cavity 37, from the bottom of which projects the end of the spindle on the network side 28. The external periphery of the connection 21 comprises a frustoconical wall 38 forming a guide surface and providing the dielectric tightness, thus a support collar 39 for a fixing flange 40. This connection 21 is intended for

  work on a clamp 43 from start 3 of the medium voltage switchboard 1.

  The multifunctional electrical connection is produced by placing the core of the connection in a mold, slightly stressed in tension by its ends, then by injecting the cold silicone with a slight overpressure, by heads distributed in a ring around the core. In a second step, the external cylindrical wall of the sheath is covered with a conductive film of silicone charged with carbon particles, by spraying paint. Likewise, a film by

  paint is deposited on the inside surface of the load side socket cup.

  Referring to Figure 3, a second embodiment of the invention is shown. The elements identical to those of the first embodiment, use the same reference signs. This second embodiment is distinguished from the first by the presence of a rigid elbow conductor section 44, the ends of which are oriented 90 from one another. This arrangement makes it possible to further reduce the overall size of the link in service, at the cost of degrading the freedom of positioning. It constitutes an advantageous compromise, when freedom of positioning is desired only in the plane

  in Figure 3 and not outside this plane.

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  Naturally, the invention is subject to various variations. In particular, it may be advantageous to use different materials for the different parts of the connection, depending on the desired mechanical characteristics. More specifically, it is possible to form the body of the bushing in a very rigid material and to adhere thereto the elastomeric material of the socket on the load side and that of the flexible electric wire. It is also possible to use different elastomers for the load and wire side grip. The elastomers taken into account are not only cold vulcanizable silicones: others

  classes of silicone, in particular hot vulcanizable silicones, can be used.

  Finally, other elastomeric materials are also possible.

  The external shielding may include a metallic tubular braid.

  The metallic braid of the core may be a relatively flat braid or, more generally,

  not cylindrical. In this case, the mechanical characteristics in bending are not isotropic.

  In the previous exemplary embodiments, the tank contains oil. However, the invention is also applicable to devices immersed in other liquid dielectrics or

  gaseous, especially in sulfur hexafluoride.

  In addition, the specific internal connection to a fuse can be replaced by any other

  type of connection as required.

  The exemplary embodiments relate to medium voltage which, within the meaning of the present application, is part of high voltage. However, the invention can also be applied beyond 56kV. The electrical equipment inside the tank can either be a load

  or a power source.

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Claims (10)

  1. One-piece high voltage electrical connection (20) intended for the transport of electrical energy between an electrical apparatus (4) disposed inside a confinement tank (9) containing a liquid or gaseous dielectric (16) and comprising an orifice, and an electrical installation external to the tank, the connection (20) comprising: * an internal end intended to be disposed inside the tank; * an outer end intended to be disposed outside the tank; ò an electrically conductive core (25) extending between the two ends; * an electrically insulating envelope enveloping the core and comprising a bushing (23) capable of being inserted into the orifice and of electrically isolating the core from the wall of the tank (9), this bushing comprising means for closing off the orifice and attachment to the wall of the tank (9), capable of cooperating with complementary fixing means so as to establish the seal between the inside and the outside of the tank (9) at the level of the 'orifice; characterized in that it further comprises, between its outer end and the crossing, a flexible electric wire (22) comprising a deformable metallic conductor (27) constituting a part of the core of the connection and an insulating sheath (26) tubular made of elastomeric material constituting part of the insulating envelope of the connection and   enveloping the deformable conductor (27).   2. One-piece electrical connection according to claim 1, characterized in that the dimensional and mechanical characteristics of the flexible electric wire (22) are such that the latter is capable of bending in at least one reference plane of at least 90 per share.   and on the other side of a median reference position.   3. One-piece electrical connection according to any one of the preceding claims,   characterized in that the insulating sheath (26) of the flexible electric wire (22) is molded on   the part of the soul that it envelops.   4. One-piece electrical connection according to any one of the preceding claims,   characterized in that the part of the core included in the flexible electric wire (22)   comprises a braid (27) made up of several braided metal wires.   5. One-piece electrical connection according to any one of the preceding claims,   characterized in that the part of the core included in the flexible electric wire (22) comprises a coating (30) of elastomer loaded with conductive particles, coating the   or the deformable conductors (27). 9 2784246   6. One-piece electrical connection according to any one of the preceding claims,   characterized in that it comprises an outer shield (31), comprising at least one film comprising an elastomer loaded with conductive particles or a tubular braid or a sheath overmolded with elastomer loaded with conductive particles or a combination of the previous ones.   7. One-piece electrical connection according to any one of the preceding claims,   characterized in that at least one or both ends of the link have   a connection interface (21, 24).   8. One-piece electrical connection according to claim 7, characterized in that the connection interface (24) comprises an insulating envelope (34) in the same material   elastomer as the envelope coating the core.   9. One-piece electrical connection according to claim 7 or claim 8, characterized in that the connection interface (24) constitutes the end of the connection intended to be inside the tank (9) and comprises a sheath of connection (34) of a terminal (11) of a fuse (10), able to deform elastically so as to envelop the terminal (11) of the fuse (10) and to ensure sealing and electrical insulation between the fuse terminal (11) and the interior of the tank.   10. One-piece electrical connection according to any one of the preceding claims, (11)   characterized in that the envelope is made of an elastomeric material molded on blade.