FR2974460A1 - HIGH OR MEDIUM VOLTAGE ELECTRICAL ASSEMBLY COMPRISING AN INSULATING DISC FORMING A CONDUCTIVE BAR BRACKET (S) AND A METAL ENVELOPE WITH A PAIR OF DISC RETAINING BRACKETS - Google Patents

Abstract

The invention relates to an electrical assembly comprising at least one metal casing (3, 4) containing an insulating gas, such as SF6, and comprising a pair of flanges (30, 40) assembled together while being at least partially supported. against each other and between which is housed at least one peripheral seal (10.1, 10.2, 10) for sealing gas; at least one electrically conductive bar (5, 6) arranged inside the metal casing, an electrically insulating disc (1) comprising at least one opening opening on the two main faces of the disc and traversed by the bar conductive. According to the invention, the electrically insulating disc (1) comprises at its periphery a flange (9) held clamped by the two flanges (30, 40) inside the peripheral sealing zone delimited by said seal.

Description

1 HIGH OR MEDIUM VOLTAGE ELECTRICAL ASSEMBLY COMPRISING AN INSULATING DISC FORMING A CONDUCTIVE BAR BRACKET (S) AND A METAL ENVELOPE WITH A PAIR OF DISC RETAINING BRACKETS

TECHNICAL FIELD The invention relates to a new electrical assembly, high or medium voltage, comprising an insulating disk forming a busbar support and a metal casing pair of retaining flanges of the disk. The main application targeted is the crossing part of three-phase shielded gas-insulated substations high voltage, typically greater than 52kV, or GIS (abbreviation of "Gas Insulated Switchgear"). The invention can also be applied to a gas insulated power transmission line or GIL (abbreviation in English of "Gas Insulated Line"). PRIOR ART In the field of high voltage electrical equipment, many solutions for mounting electrically conductive elements on an electrical insulating support are known in a metal casing containing a dielectric insulating gas, such as SF6. More particularly, in the GIS cross-over parts, it is widely known to arrange an insulating support for shielded bars in the metal shell or vessel.

Thus, it is known from patent JP 2007181294, to support in a bushing 1 a high-voltage metal conductor, single phase, 2 by an insulating spacer 5 inside a tank 3 grounded. The insulating spacer 5 comprises an opening at its center through which the conductor 2 is housed in alignment with the axis of the vessel 3. The general shape of the spacer 5 is frustoconical. The arrangement disclosed according to this patent implies that in case of realization of three-phase current crossing part, three crossings 1 independent or otherwise separated are required. This implies a significant cost for in situ implantation. In addition, the frustoconical shape of the insulating spacer 5 implies a large footprint along the axis of the crossing. The patent KR 20090072582 discloses a gas-insulated high voltage crossing, with an arrangement of three conductors 12a supporting a metal tank each by an insulating support 120 and by means of support elements 110. More exactly, the conductors 12a are individually adjusted in an electrically insulating support 120 themselves individually adjusted in one of the support members 110 attached to the tank. Thus, according to this patent, it is necessary to have a number three electrically insulating supports 120 and three separate support elements 110 to support the three three-phase conductors 12a by the metal vessel. In other words, the major disadvantage of the arrangement according to this patent lies in the number of important parts and therefore in the related cost. Finally, patent DE 4302424 discloses a high voltage circuit breaker-disconnector 12 under gas isolation, with shielded bars 10 and three disconnectors 40 whose movable contacts 42 are each supported by an electrically insulating support 17 itself supported by a first support beam 124, the fixed contacts 44 each being supported by another electrically insulating support 11 itself supported by a second support beam 126.

It follows from this patent, that the support beams 124, 126 are electrically conductive and are common to all three phases. As shown in FIGS. 4 and 9, the shape of the support beams 124, 126 and their relative arrangement imply that they are capable of bending. However, a curvature of a beam with openings for the active parts carrying the alternating currents can generate vibrations under the effect of Lorentz forces. These vibrations are highly detrimental in high voltage electrical equipment because they significantly increase the emission noise of the equipment in question. In addition, there is a risk of electrical discharge between active parts and support beams 124, 126. This risk is particularly present when the mechanical wear of the disconnectors 40 causes gravity particles on the lower beam 126. 4 The purpose of invention is therefore to propose a mounting solution of one or more electrical conductive elements on an electrical insulating support in a metal casing containing a dielectric insulating gas of a high voltage electrical assembly which overcomes all or part of the disadvantages of the art prior. SUMMARY OF THE INVENTION To this end, the subject of the invention is an electrical assembly comprising at least one metal casing containing an insulating gas, such as SF6, and comprising a pair of flanges assembled together, being at least partly supported against each other and between which is housed at least one peripheral seal for sealing gas; at least one electrically conductive bar arranged inside the metal casing, an electrically insulating disc comprising at least one aperture opening on the two main faces of the disk and traversed by the conductive bar. According to the invention, the electrically insulating disc comprises at its periphery a flange held clamped by the two flanges inside the peripheral sealing zone delimited by said seal. Preferably, the flange of the disc is kept pinched at least partly inside the seal. The seal may advantageously comprise two distinct surfaces, each being housed in a groove of flanges and the flange of the disc being clamped in part between the two joint surfaces. The flange preferably has a thickness d2 less than the thickness d1 of the disk body at their junction, the thickness of the flange decreasing outwardly. Advantageously, at least one shielding screen mounted in an opening of the insulating disc may be provided, each shielding screen being adapted to house a conducting bar and to at least reduce the corona effect at the interface between the screen, the conductive bar and the insulating disk. electric. It is also advantageous to provide a spring device arranged between a shielding screen and the electrical insulating disk to allow any movement of the conductive bar housed in the screen. This makes it easier to design the electrical assembly according to the invention: indeed, such a spring device makes it possible to fix each conductor bar inside an ajour during assembly in production. The electrical assembly according to the invention advantageously comprises three shielded bars each of a phase of a three-phase electrical equipment. Preferably, the three centers of shielding screens each housing a conducting bar form an isosceles triangle whose center of symmetry is distinct from that of the insulating disc. Such a shift between centers of symmetry makes it easy to ensure compatibility between different devices 6 of a shielded station (in English "Gas Insulating Switchgear", that is to say abbreviated G.I.S). Indeed, such a GIS substation or substation is generally composed of several partitions (bushings), and it is necessary to shift the centers of symmetry to adapt the set of busbars to different diameters of the partitions and thus maintain the same distances between the busbars of different devices.

Advantageously, the seal is metallic to ensure the continuity of electrical connection from one flange to another. The electrical assembly according to the invention may constitute a passage portion of a high voltage electrical equipment or a high voltage gas insulated line (GIL) line. Thanks to the assembly according to the invention, it is possible to support three three-phase conductor elements by one and the same electrically insulating disc in the same crossing, which is advantageous in terms of cost. For an application as a three-phase high-voltage bushing, it is possible to envisage a thickness of the body of the insulating disk d1 of the order of 15 mm. This value is to be compared for example with the frustoconical insulating support of patent JP 2007181294 mentioned in the preamble which typically extends over a length of the order of 100 mm in the longitudinal direction of the bushing. Thus, compactness of the assembly according to the invention can be considered at least six times higher than the assembly according to the patent JP 2007181294. Compared to a mounting such as that according to the patent KR 20090072582 cited in the preamble, a single insulating support according to the invention. invention instead of trios is required. Finally, compared to an assembly such as that according to DE 4302424, no electrically conductive support is required according to the invention to support the current conducting bars. Thus, thanks to the invention, the absence of electrically conductive supports near the active parts significantly reduces the risk of electric shock within the assembly. However, as described in chapter 2.3.1.3 of the Cigré technical brochure 150, published in February 2000, more than 25% of failures (failures) are due to electrical discharges to earth. Thus, the mounting solution according to the invention significantly improves the efficiency of high voltage electrical equipment. BRIEF DESCRIPTION OF THE DRAWINGS Other advantages and characteristics of the invention will emerge more clearly on reading the detailed description of an embodiment of the invention made, by way of illustration and without limitation, with reference to the figures among which: FIG. 1 is a perspective view in partial section of an electrical assembly according to the invention, the busbars of the assembly being high voltage busbars, FIG. 2 is a longitudinal sectional view in detail of FIG. the flange pair assembly of the assembly according to Figure 1; - Figure 3 is a perspective view of an insulating disc forming a busbar support of an electrical assembly according to the invention.

DETAILED DESCRIPTION OF PARTICULAR EMBODIMENTS In FIG. 1, an electrical assembly according to the invention is shown in an application as part of a SF6-type gas-insulated high-voltage three-phase apparatus.

In other words, here the busbars of which only two, six, six are represented constitute shielded bars to conduct each part of the three-phase current. The electrical assembly according to the invention comprises an electrically insulating disc 1 whose flange at its periphery is held pinched by a bolted assembly 2 with two flanges 30, 40 each end of a metal casing 3, 4. This assembly accomplishes the mechanical and electrical connection of the two metal shells 3, 4 of electrically conductive material. The inside of these envelopes 3, 4 is filled with dielectric insulating gas, such as SF6. The disk 1 forms the support of the three shielded bars for the passage of the three-phase current of which only two are exposed, the only one being represented in the cut-away part of FIG. 1. Typically, the metallic shells 3, 4 are to the ground and each armored busbar 5, 6 is raised to a high voltage potential in three-phase current. Thus, the electrically insulating disc 1 ensures both the electrical insulation between each of the shielded bars and between all of them and the two metal shells 3, 4 grounded.

Each of the busbars 5, 6 is fitted into a shielding screen 7, 8, 11 of electrically conductive material or semiconductor. The function of these screens 7, 8, 11 is to ensure protection of the electrical assembly against the corona effects due to the high electric fields at the interfaces between the shielded bars 5, 6, screens 7, 8 and electrically insulating disk 1. Each 7, 8, 11 is inserted in an opening of the disc 1 as better explained below and thus surrounds one of the armored bars 7, 8, 11. In fact, the electrically maintained insulating disc according to the invention supports the weight of the three shielding screens 7, 8, 11 and three armored bars 5, 6 each fitted into a screen.

In the illustrated embodiment, the three bars 5, 6 are cylindrical solid and identical to each other and the shielding screens 7, 8, 11 are hollow cylinders with an internal diameter corresponding to the external diameter of the bars at the mounting clearance and they are identical to each other. The mechanical assembly according to the invention between the electrically insulating disc 1 and the flanged joint assembly 2 is shown in more detail in FIG.

The electrically insulating disc 1 has in its central part, a body 1 of substantially equal thickness d1 over its entire surface and at its periphery, a fastening flange 9 integral with the body. Typically, the disc 1 is molded in one piece. The flange 9 has a thickness approximately equal to d2 at the junction with the body and which decreases towards the outside until reaching a minimum value. As an indication, we can have the following values: dl = 8 mm; d2 = 6.8 mm; minimum value at the end of the flange 9 = 5.5 mm.

The fastening flange 9 is held pinched, in its tapered portion of thickness less than d2, between two annular sealing surfaces 10.1, 10.2 which form the seal 10 of the flange assembly 30, 40. The two surfaces 10.1, 10.2 seal ring may each be inserted into a peripheral groove provided for this purpose at the end of the flanges 30, 40. In other words, the two annular sealing surfaces 10.1, 10.2 pinch the flange 9 on both sides with a force sufficient clamping not only to support the weight of the shielded bars 5, 6 and shields 7, 8, 11 but also 11 to seal the insulating gas inside the metal shells 3, 4 with respect to outside. FIG. 3 shows in more detail the assembly of the shielding screens 7, 8, 11 in the insulating disk 1. Here, the isosceles triangle formed by the centers of the axes of the screens 7, 8, 11 has a center of symmetry which does not coincide with the center of symmetry of the insulating disc 1.

Between each opening of the insulating disk dedicated to the housing of a screen shield 7, 8, 11 and the latter is provided a spring device 12, 13, 14. In the illustrated embodiment, the three spring devices 12, 13 , 14 are made integrally in the insulating disc by making openings of appropriate dimensions, the thicknesses of the electrically insulating material constituting the disc 1 providing flexibility. Thus, when the armored bars 5, 6 are each fitted in a corresponding screen 7, 8, 11, they are physically supported by the insulating disk with a possible displacement due to the spring devices 12, 13, 14 (Figure 3). The invention which has just been described makes it possible to obtain an insulating support that is electrically reliable and easy to use conducting bars in a metal casing containing a dielectric insulating gas. Although described in detail only for application as a crossing of high voltage electrical equipment, the invention may also be suitable as part of a high voltage gas insulated line (GIL).

Claims (11)

REVENDICATIONS1. Electrical assembly comprising at least one metal casing (3, 4) containing an insulating gas, such as SF6, and comprising a pair of flanges (30, 40) assembled together while being at least partially supported against each other and between which is housed at least one peripheral seal (10.1, 10.2, 10) for sealing the gas; at least one electrically conductive bar (5, 6) arranged inside the metal casing, an electrically insulating disc (1) comprising at least one opening opening on the two main faces of the disc and traversed by the bar conductor, wherein the electrically insulating disc (1) comprises at its periphery a flange (9) held clamped by the two flanges (30, 40) within the peripheral sealing zone delimited by said seal. 2. Electrical assembly according to claim 1, wherein the flange (9) of the disc is kept clamped at least partly inside the seal (10.1, 10.2). An electrical assembly according to claim 2, wherein the seal comprises two distinct surfaces (10.1, 10.2), each accommodated in a flange groove (30, 40) and the flange (9) of the disc being pinched in part between the two surfaces (10.1, 10.2) of joint (10). 14 4. Electrical assembly according to one of the preceding claims, wherein the flange has a thickness d2 less than the thickness dl of the disk body at their junction, the thickness of the flange decreasing outwardly. 5. Electrical assembly according to one of the preceding claims, wherein at least one shielding screen (7, 8, 11) is mounted in an opening of the insulating disc, each screen shield being adapted to house a conductor bar and for less reduce the corona effect at the interface between screen, conductor bar and electrical insulating disc. 6. Electrical assembly according to claim 5, wherein a spring device (12, 13, 14) is arranged between a shielding screen and the electrical insulating disk to allow any movement of the conductive bar housed in the screen. 7. Electrical assembly according to one of the preceding claims, comprising three shielded bars (5, 6) each of a phase of a three-phase electrical equipment. 8. Electrical assembly according to claim 7, wherein the three centers of shielding shields each housing a busbar form an isosceles triangle whose center of symmetry is distinct from that of the insulating disc. 9. Electrical assembly according to any one of the preceding claims, wherein the seal (10, 10.1, 10.2) is metallic to ensure continuity of electrical connection from one flange (30) to another (40). 10. Electrical assembly according to any one of the preceding claims, constituting a passage portion of a high voltage electrical equipment. An electrical assembly as claimed in any one of claims 1 to 9, constituting a high voltage gas insulated line portion (GIL).