AU5260699A

AU5260699A - A monobloc multifunctional high voltage electrical connection, comprising a bushing and a connecting interface to a fuse, and a protective device comprising such an electrical connection

Info

Publication number: AU5260699A
Application number: AU52606/99A
Authority: AU
Inventors: Jean-Pierre Kersusan; Victor Pennucci; Maurice Perrin
Original assignee: Schneider Electric Industries SAS
Current assignee: Schneider Electric Industries SAS
Priority date: 1998-10-01
Filing date: 1999-09-30
Publication date: 2000-04-06
Also published as: AR021496A1; DE69916391T2; CN1250216A; CN1171254C; FR2784245A1; ATE264541T1; NO994686L; ES2217713T3; EA199900786A2; FR2784245B1; EP0991090B1; PT991090E; EA199900786A3; NO994686D0; EP0991090A1; DE69916391D1; NO318756B1; EA002206B1

Description

rIUUU I I 28/a1 Regulation 3.2(2)

AUSTRALIA

Patents Act 1990

ORIGINAL

COMPLETE SPECIFICATION STANDARD PATENT .9 a.

a Application Number: Lodged: Invention Title: A MONOBLOC MULTIFUNCTIONAL HIGH VOLTAGE ELECTRICAL CONNECTION, COMPRISING A BUSHING AND A CONNECTING INTERFACE TO A FUSE, AND A PROTECTIVE DEVICE COMPRISING SUCH AN ELECTRICAL CONNECTION 9 The following statement Is a full description of this Invention, Including the best method of performing it known to us 1 A MONOBLOCK MULTIFUNCTIONAL HIGH VOLTAGE ELECTRICAL CONNECTION, COMPRISING A BUSHING AND A CONNECTING INTERFACE TO A FUSE, AND A PROTECTIVE DEVICE COMPRISING SUCH AN ELECTRICAL

CONNECTION

The invention relates to an electrical connection designed for electrical power supply of a high voltage apparatus, protected by a fuse connected in series between the electrical power supply source and the apparatus, the fuse being at least partially immersed in a protective tank containing a liquid or gas dielectric.

The document EP-A-0,224,072 describes a three-phase transformer immersed in a tank containing a liquid dielectric, in this instance oil, and power supply whereof is performed via an electrical connection comprising a high voltage bushing between the outside and the inside of the tank. The transformer primary circuit is protected by S-fuses located inside the tank, the characteristics of which fuses are such that they respond only to electrical faults corresponding to internal faults of the transformer. In this type of installation, precautions have to be taken against risks of an electrical arc forming between a transformer primary winding and the bushing. From such an arc there would in fact result a short-circuit not flowing through the fuse, so that the fuse would not be able to interrupt it. To limit this risk, the document indicates on the one hand that the fuse has to be arranged in such a way that the distance between the bottom end of the bushing for the high voltage and the top end of the fuse is less S.than half the length of the fuse, aftd on the other hand that the conductor section between the bottom end of the bushing for the high voltage and the fuse has to be achieved in such a way as not to form a point of departure for an electrical arc, by enclosing the conductor section situated between the bottom end of the bushing for the high voltage and the fuse in pieces of insulating tubing jointed to one another by binding, and/or by providing the fuse with a frustum-shaped protective shield made of insulating material, which opens in the direction of the bushing for the high voltage.

Such an arrangement complicates assembly and disassembly of the bushing and fuse. In addition, the form of the frustum-shaped shield, although it is able to provide protection against the risks of an arc forming between a winding and the bushing, does not provide a good protection against the risk of breakdown of an arc between the bottom ends of two adjacent bushings, in particular at the level of the fuse heads, and even more so between a fuse and the walls of the tank, in particular in case of a decrease of the level or quality of the dielectric in the tank.

The object of the present invention is to simplify assembly and disassembly of an electrical connection of the previous type. Its object is also to propose a simple and inexpensive electrical connection able to be used for power supply of a medium voltage electrical apparatus protected by a fuse, reducing the short-circuit risks at the level of the power supply side terminal of the fuse, in particular in case of a decrease of the level or quality of the dielectric.

These objects are achieved by means of an electrical connecting device designed for transporting energy between the high voltage electrical power supply system and a protective fuse protecting an electrical apparatus constituting a load and located inside a tank containing a liquid or gas dielectric and comprising an orifice, the fuse comprising two terminals, one on the power supply side and the other on the load side, the load-side terminal being located inside the tank, the two terminals of the fuse being connected by a fuse element contained in a dielectric body, the device ".:comprising: an electricity conducting core; a power supply side connecting interface designed for electrical connection of the core with the electrical power supply; a bushing designed to be inserted in the orifice and comprising means for sealing the orifice and for fixing to the wall of the tank designed to achieve the tightness between the inside and outside of the tank at the level of the orifice and to electrically insulate the core from the wall of the tank; a load-side connecting interface designed for electrical connection of the core with the power supply side terminal of the fuse; a device wherein the load-side connecting interface comprises a sheath made of elastomer material able to be deformed elastically so as to envelop the power supply side terminal of the fuse and to achieve the tightness and electrical insulation between the power supply side terminal of the fuse and the internal medium of the tank.

The power supply side terminal of the fuse is preferably, but not necessarily, situated inside the tank, in particular for shock-resistance and rigidity reasons.

3 Preferably, the sheath comprises at least one wall including an electrically conducting coating. The coating is then at the potential of the fuse terminal. This limits the risks of ionization of the air by corona effect between the fuse terminal and the sheath. The coating can take the form of an elastomer layer charged with conducting carbon particles, or of a film of conducting material. Alternatively, the inside of the sheath can be covered by a metallic skirt in the shape of a cup, made flexible by the presence of axial peripheral slots. This skirt can for example be crimped onto the end of the core, the elastomer sheath then being overmoulded on this skirt. It is also possible to combine a metallic skirt and a conducting film.

Preferably, the sheath comprises a lip designed to operate in conjunction with the body of the fuse so as to achieve the tightness between the dielectric of the tank and the inside of the sheath. This arrangement enables the insulation of the fuse terminal to be perfectly mastered.

Advantageously, the bushing comprises a coating made of elastomer material 00 °moulded with the sheath. This arrangement gives the bushing advantageous mechanical properties, and in particular a certain elasticity in flexion and torsion, which allow a mechanical decoupling between the power supply system and load.

Such a decoupling is useful in particular when the load is subjected to mechanical vibrations. In addition, manufacture of the electrical connection is particularly simple in this case.

Preferably, the device comprises a deformable electrical wire with an insulating cladding made of elastomer material enveloping one or more electrical conductors forming a part of the core of the device. In the case where the deformable electrical wire is located outside the tank, the connection enables a set of connectors to be eliminated in comparison with conventional devices. It also allows a great freedom of positioning of the electrical apparatus. Alternatively, the wire can be located inside the tank, between the bushing and the load-side connector. It is also possible to combine an electrical wire outside the tank and an electrical wire inside the tank.

Advantageously, the insulating cladding of the electrical wire is made of the same elastomer material as that of the sheath which enables the different parts of the device to be moulded in a single manufacturing stage.

The expression electrical wire designates in the present application in generic manner deformable long electrical conductors, constituted for example by interwoven metallic strands. The electrical wire preferably comprises a braid of conducting strands. The braided cable, i.e. criss-crossed relatively flat in the manner of a plait, gives a much greater flexibility than conventional stranded cables. For currents of lower intensity, stranded or wire cables are able to offer an alternative.

Another feature of the invention relates to the protective device of a medium voltage S* electrical apparatus in particular a transformer housed in a tank containing a liquid or gas dielectric and comprising an orifice, this device comprising: a protective fuse at least partially located inside the tank and connected between the power supply and the apparatus, the fuse comprising two terminals, one on the power supply side and the other on the load side, connected by a fuse element contained in a dielectric body, the load-side terminal being located inside the tank, and an electrical connection device as described above, whose load-side connecting interface is connected to the power supply side terminal of the fuse.

Such a device guarantees a high-quality insulation between the fuse and the inside of the tank.

Another feature of the invention relates to an electrical apparatus constituting a load supplied by a high voltage electrical power system, located inside a tank containing a liquid or gas dielectric and comprising an orifice, and provided with a protective device as previously described, arranged between the electrical power supply system and the electrical apparatus.

Other advantages and features of the invention will become more clearly apparent from the following description of different embodiments of the invention, given as non-restrictive examples only and represented in the accompanying drawings in which Figure 1 represents a cross 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 represents a longitudinal sectional view of the electrical connection of figure 1, in a reference position Figure 3 represents a longitudinal sectional view of an electrical connection according to a second embodiment of the invention; Figure 4 represents a longitudinal sectional view of an electrical connection according to a third embodiment of the invention.

With reference to figure 1, a medium voltage electrical switchboard 1, confined in an enclosure 2 filled with a gas dielectric, in this case sulphur hexafluoride, comprises feeders 3 delivering the power system current to an electrical apparatus 4 constituting S-a load. This apparatus 4 comprises a three-phase medium voltage I low voltage transformer 5, and a protective device comprising a three-phase circuit breaker 6 and fuses 10, connected line-side of the primary windings of the transformer 5. The circuit breaker 6 is designed for protection against electrical faults inducing only small current surges at the level of the transformer primary, in particular faults occurring on S.the secondary windings. Each fuse 10 is connected in series between the power system and the circuit breaker and is selectively sensitive to the short-circuits affecting the primary windings of the transformer 5. A detailed description of this S. device can be found in the French Patent Application bearing the national record number 98/10519. Each fuse 10 comprises, in conventional manner, two metallic end terminals 11, 12 connected by a fuse element 13 contained in a cylindrical body 14 comprising a solid dielectric material. The electrical apparatus 4 is housed in a tank 9 composing a tightly sealed container filled with a dielectric fluid 16, in this instance oil.

An electrical connection 20 according to the first embodiment of the invention, represented in figures 1 and 2, is designed for electrical power supply of the primary windings of the transformer and is connected on the one hand to the power supply system at the level of the feeders 3 and on the other hand to the apparatus 4. This electrical connection 20 comprises an external connection 21 designed for connection with the power supply system, a middle part constituting a flexible electrical wire 22, a bushing 23 ensuring the tightness at the level of an orifice made 6 in a wall of the tank 9, and an internal connection 24, in which the terminal 11 of the fuse 10 engages.

The electrical connection 20 comprises an electricity conducting core 25 covered by a covering 26 made of good insulating elastomer material. The core 25 comprises in its middle part a braid 27 composed of metallic strands and, at each end, a pin 28, 29 crimped onto the braid 27. The core 25 comprises in addition a conducting coating covering the metal braid 27. The coating layer 30 enables the effects of spikes of the strands protruding out radially from the braid 27 to be eliminated and the equipotential surfaces in the vicinity of the irregularities of the surface of the braid to be smoothed. In practice, the conducting coating 30 is formed by a silicone substrate charged with conducting carbon particles.

The covering 26 is, in this embodiment, formed by a cold vulcanizable silicone of .i general cylindrical shape, which also constitutes the body of the bushing and of the power supply side and load-side connections. The covering 26 is covered by a cladding formed by a conducting film 31 which is at the same potential as the ground.

As an indicative example, for a rated voltage of 24 kV and a rated current of 100 A, the diameter of the braid is about 8 mm, for an external diameter of the cable of about 30 mm. As can be seen in the rest position of figure 2 and the operating position of figure 1, the connecting cable 20 is able to be flexed at a large angle, i.e.

at least 1800. In other words, when one of the ends of the connection, for example the internal end, is fixed, the other is able to move in reversible manner from a first ~reference position for example the rest position of figure 2 to a second position in which it has undergone a 1800 rotation in the example, the position of figure 1. In this instance this flexion is possible in all the planes of the space, on each side of the rest position. These degrees of freedom enable the free end of the connection to be positioned without excessive stresses.

The bushing 23 and internal connection 24 are, in this embodiment, embedded in one another. The bushing 23 comprises a fixing flange 32 which is fixed onto 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 flowing through the connection 20. The internal connection 24 comprises a sheath 34 a part whereof is in the shape of a cup having approximately the same shapes as the power supply side terminal of the fuse, with a cylindrical wall and a flat base flush with the load-side end of the pin 29 of the conducting core of the connection 20. This cup is extended as a cylindrical lip 36 of slightly smaller diameter so as to take the shape of the body 14 of the fuse. The internal walls of the cup 35 are covered with a conducting film in such a way that they are at the same potential as 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 operates in conjunction with the cylindrical body 14 of the fuse and undergoes a flexible deformation which enables a sufficient contact pressure with the body of the fuse to be ensured, so that a tight seal is formed between the inside of the cup 35 and the external medium immersed in the dielectric fluid of the tank 9.

The external connection 21 comprises a cavity 37 in the form of a cup, from the bottom of which the power supply end of the pin 28 protrudes out. The external *circumference of the connection 21 comprises a frustum-shaped wall 38 forming a guide surface and achieving the dielectric tightness, and a support collar 39 for a :fixing flange 40. This connection 21 is designed to engage on a grip contact 43 of the feeder 3 of the medium voltage switchboard 1.

The multifunctional electrical connection is manufactured by placing the core of the connection in a mould, slightly biased in traction via its ends, and then injecting the silicone cold with a slight overpressure, by heads distributed in a ring around the core. In a second stage, the external cylindrical wall of the cladding is covered with a conducting silicone film charged with carbon particles, by paint projection. Likewise, a i: film of paint is deposited on the internal surface of the cup of the load-side connector.

With reference to figure 3, a second embodiment of the invention is distinguished from the first by the absence of a section of flexible electrical wire. Connection to the power supply system is then achieved by means of a separate cable which plugs into the power supply side connection 21.

Figure 4 represents a third embodiment of the invention. Here, the power supply side connection 21 is situated in the bushing, which is connected to the load-side connection 24 by means of an electrical wire 50 of identical structure to that of the first embodiment. Freedom of positioning of the fuse with respect to the bushing is thus obtained.

8 Naturally, the invention is subject to different variations. In particular, it may be advantageous to use different materials for the different parts of the connection, according to the mechanical characteristics required. More precisely, it is possible to form the body of the bushing from a very rigid material and to make the elastomer material of the load-side connection and that of the flexible electrical wire adhere thereto. It is also possible to use different elastomers for the load-side connection and the wire. The elastomers involved are not only cold vulcanizable silicones other silicone classes, in particular hot vulcanizable silicones, can be used. Finally other elastomer materials can also be envisaged.

In the above embodiments, the fuse is located totally inside the tank, on one side of the middle plane of the cover of the tank, which constitutes a protection against shocks. However, the invention keeps its advantages when the power supply side S0: connection of the fuse is situated above this middle plane, so long as the load-side terminal of the fuse is immersed in the dielectric fluid and makes mastery of the lineside insulation of the fuse body necessary.

The specific shapes of the cup of the load-side connector of the connection are dictated by the corresponding shapes of the fuse and vary from one fuse to the other.

The important thing is to shape the sheath lip in such a way as to achieve a flexible deformation generating a sufficient contact pressure of the elastomer material of the connector on the body of the fuse. The cup is also shaped according to the shape of the fuse terminal. It is also possible to provide for the fuse head to be screwed into the cup.

In the above embodiments, the tank contains oil. However, the invention is also applicable to switchgear apparatuses immersed in other liquid or gas dielectrics, in particular in sulphur hexafluoride.

Furthermore, the protective device comprising the electrical connection and the fuse can be used for any type of apparatus immersed in oil or in a dielectric gas. In particular, it is applicable to an intermediate circuit breaker transformer.

9 The embodiments concern medium voltage which, in the sense of the present application, forms part of high voltage. However, the invention can also be applied above 56 kV.

"Comprises/comprising" when used in this specification is taken to specify the presence of stated features, integers, steps or components but does not preclude the presence or addition of one or more other features, integers, steps, components or groups thereof.

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Claims

1. An electrical connecting device (20) designed for transporting energy between the high voltage electrical power system and a protective fuse (10) protecting an electrical apparatus constituting a load and located inside a tank containing a liquid or gas dielectric (16) and comprising an orifice, the fuse (10) comprising two terminals, one (11) on the power supply side and the other (12) on the load side, the load-side terminal (12) being located inside the tank the two terminals (11, 12) of the fuse (10) being connected by a fuse element (13) contained in a dielectric body the device (20) comprising: San electricity conducting core (25) a power supply side connecting interface (21) designed for electrical connection of the core (25) with the electrical power supply; a bushing (23) designed to be inserted in the orifice and comprising .i means for sealing the orifice and for fixing to the wall of the tank designed to achieve the tightness between the inside and outside of the tank at the level of the orifice and to electrically insulate the core from the wall of the tank e a load-side connecting interface (24) designed for electrical connection of the core (25) with the power supply side terminal (11) of the fuse; characterized in that the load-side connecting interface (24) comprises a sheath (34) made of elastomer material able to be deformed elastically so as to envelop the power supply side terminal (11) of the fuse and to achieve the tightness and electrical insulation between the power supply side terminal (11) of the fuse and the internal medium of the tank

2. The device according to claim 1, characterized in that the sheath (34) comprises at least one wall including an electrically conducting coating.

3. The device according to either one of the foregoing claims, characterized in that the sheath (34) comprises a lip (36) designed to operate in conjunction with the body (14) of the fuse (10) so as to achieve the tightness between the dielectric (16) of the tank and the inside of the sheath (34). 11

4. The device according to any one of the foregoing claims, characterized in that the bushing (23) comprises a coating made of elastomer material moulded with the sheath (34). The device according to any one of the foregoing claims, characterized in that it comprises a deformable electrical wire (22) with an insulating cladding (26) made of elastomer material enveloping one or more electrical conductors forming a part of the core (25) of the device.

6. The device according to claim 5, characterized in that the deformable electrical wire (22) is located outside the tank eeoc S" 7. The device according to either one of the claims 5 or 6, characterized in that the insulating cladding (26) of the electrical wire (22) is made of the same elastomer o material as that of the sheath (34).

8. The device according to any one of the claims 5 to 7, characterized in that the "T •electrical wire (22) comprises a braid (27) of conducting strands. S S o

9. A protective device of a medium voltage electrical in particular a transformer housed in a tank containing a liquid or gas dielectric and comprising an orifice, this device comprising: Sa protective fuse (10) at least partially located inside the tank and connected between the power supply and the apparatus the fuse comprising two terminals, one (11) on the power supply side and the other (12) on the load side, connected by a fuse element (13) contained in a dielectric body the load-side terminal (12) being located inside the tank and San electrical connection device (20) according to any one of the claims 1 to 8, whose load-side connecting interface (24) is connected to the power supply side terminal (11) of the fuse. An electrical apparatus constituting a load supplied by a high voltage electrical power system, located inside a tank containing a liquid or gas dielectric (16) and comprising an orifice, and provided with a protective device according to claim 9, arranged between the electrical power system and the electrical apparatus. DATED this 30th day of September 1999. SCHNEIDER ELECTRIC INDUSTRIES SA WATERMAK PATENT TRADEM'ARK ATTORNEYS 290 BURWCX)D ROAD HAWTHORN. VIC. 3122. S *S S S. S S* S. 5 S 0 S S 0t @555 S. S. S 4 0 S5 00 S S