AU2010249250A1

AU2010249250A1 - Device for electric connection of a bar belonging to a busbar to an electric bushing belonging to the insulating enclosure of an electric switchgear apparatus

Info

Publication number: AU2010249250A1
Application number: AU2010249250A
Authority: AU
Inventors: Francois Famy; Jean-Pierre Kersusan; Thierry Milan
Original assignee: Schneider Electric Industries SAS
Current assignee: Schneider Electric Industries SAS
Priority date: 2009-12-14
Filing date: 2010-12-13
Publication date: 2011-06-30
Anticipated expiration: 2030-12-13
Also published as: EP2333801A1; EP2333801B1; CN102104207B; FR2953977A1; FR2953977B1; AU2010249250B2; CN102104207A; AR079447A1

Abstract

DEVICE FOR ELECTRIC CONNECTION OF A BAR BELONGING TO A BUSBAR TO AN ELECTRIC BUSHING BELONGING TO THE INSULATING 5 ENCLOSURE OF AN ELECTRIC SWITCHGEAR APPARATUS. The present invention relates to an electrical connection device of at least one bar (2) belonging to a busbar to an electrical bushing (1) belonging to the insulating enclosure of an electrical switchgear apparatus, said bushing comprising a conductive insert (3) at least 10 partially surrounded by an insulating part (Id), said device comprising means (10,1Oa,10b) for performing electrical connection between an end part (2a) of the bar and said conductive insert (3), and a deflector (4) formed by a conductive shield designed to be electrically connected to the bar (2) and placed around the electrical connection area (5) between the bar (2) and said insert (3). This deflector is moulded from casting in a flexible 15 material, said material forming a sleeve (6) of substantially cylindrical shape designed, on account of the rigidity of the deflector-shield, to press via its end part situated on the side of the apparatus on the above-mentioned insulating part (ld) of the bushing (1) presenting a complementary shape, with a certain pressure so as to achieve perfect tightness between said flexible material and the insulating part of the bushing, so as to achieve an improved 20 dielectric tightness over substantially the whole of the circumference of the above mentioned bottom part of the sleeve. 25 FIGURE 1. CMj CD c 9- T qt0 9-) co cr

Description

Pool Section 29 Regulation 3.2(2) AUSTRALIA Patents Act 1990 COMPLETE SPECIFICATION STANDARD PATENT Application Number: Lodged: Invention Title: Device for electric connection of a bar belonging to a busbar to an electric bushing belonging to the insulating enclosure of an electric switchgear apparatus The following statement is a full description of this invention, including the best method of performing it known to us: P111ABAU/0610 DEVICE FOR ELECTRIC CONNECTION OF A BAR BELONGING TO A BUSBAR TO AN ELECTRIC BUSHING BELONGING TO THE INSULATING ENCLOSURE OF AN ELECTRIC SWITCHGEAR APPARATUS. 5 The present invention relates to a device for electrical connection of at least one bar belonging to a busbar to an electrical bushing belonging to the insulating enclosure of an electrical switchgear apparatus, said bushing comprising a conductive insert at least partially surrounded by an insulating part, said device comprising means for making electrical connection between an end part of the bar and said conductive insert, and a 10 deflector formed by a conductive shield designed to be electrically connected to the bar and placed around the electrical connection area between the bar and said insert. Inside such a connection interface there is an area, situated at the level of the connection of the bar and the insert, where three different materials, i.e. a conductor, a solid insulator and 15 a gas, are very close to one another at a point called "triple point". This particularity makes this area very sensitive to electrical fields. This can result in an ionization phenomenon of the surrounding gas, which has the effect of prematurely damaging the superficial dielectric strength of the product. The combination of these stresses with other factors such as water and other aggressive agents (such as pollutants 20 contained in the air, urban or industrial pollution) is an aggravating factor. More often than not, this triple point is not efficiently protected. Only a deflector is provided to obtain good dielectric performances and the bars are sheathed. This results in problems of early ageing of the bars, in particular in the polluted atmospheres mentioned above. 25 Connection devices are also known comprising a sleeve placed on the bushing and also performing sleeving of the bar, said sleeve presenting an opening at the top part thereof designed to be blanked off by a plug designed to mask access to the electrical connection. This sleeve does however necessarily have a profile matching the profile of the bushing on 30 which it is fitted.

2 The object of the present invention is to propose a device for connection of a bar to a bushing that is of simple design, enabling the ageing resistance of the busbar in difficult environments to be improved from the dielectric standpoint, said device not requiring a particular profile for the bushings and therefore being able to be fitted on all present 5 bushings. For this purpose, the object of the present invention is to provide a connection device of the above-mentioned kind, this device being characterized in that said deflector is moulded from casting in a flexible material, said material forming a sleeve of substantially 10 cylindrical shape that is able, due to the effect of the rigidity of said deflector, to press via its end part situated on the same side as the apparatus on the above-mentioned insulating part of the bushing presenting a complementary shape, with a certain pressure so as to achieve perfect tightness between said flexible material and the insulating part of the bushing, so as to ensure an enhanced dielectric tightness over substantially the whole of the 15 circumference of the above-mentioned bottom part of the sleeve. According to a particular feature, the external surface of the deflector is substantially totally coated by the flexible material, said material constituting a solid insulator, with an absence of gas between the deflector and the material, so as to enhance the efficiency of the 20 deflector-shield. In this way, the parts of the deflector presenting the highest normal electrical fields at the surface are located in a solid insulating environment of higher dielectric strength. According to another feature, the insulating part of the bushing comprises a part of conical 25 shape and a part of flared shape on the same side as the apparatus. According to another feature, the above-mentioned deflector presents a substantially conical external shape the part whereof having the largest diameter being located towards the inside of the apparatus, said deflector comprising a first part of annular shape situated 30 on the outside of the apparatus followed by a second part in the form of a disc, said second part being followed by a third part of annular shape of reduced thickness compared with the thickness of the first part and situated on the same side as the apparatus.

3 According to another feature, the above-mentioned connection means comprise a screw and a threaded bore formed in the insert. 5 According to another feature, the second part of the deflector in the form of a disc, and the end of the bar respectively comprise two facing holes designed for the above-mentioned fixing screw to pass through, the screw head being designed to press on said second part of the deflector, after the screw has been screwed into the insert, the deflector being fitted between the screw head and the end part of the bar, which end part being pressing on the 10 end part of the insert. According to another feature, the edge of the top part of the sleeve is folded towards the axis of the sleeve and then towards the inside of the apparatus along the surface of the deflector so as to form a tubular hole for the screw head to pass through. 15 According to another feature, this device comprises a plug, a resistive divider, a capacitive divider or a capacitor designed to participate in indicating the presence or absence of voltage, designed to be fitted inside the above-mentioned tubular hole. 20 According to another feature, the plug, resistive divider, capacitive divider or capacitor, is fixed by clip-fastening means inside said hole. According to another feature, the above-mentioned clip-fastening means comprise a part of increased thickness provided at the end of the sleeve situated on the outside of the 25 apparatus, followed by a part of regularly thinned thickness situated inside the tubular hole. According to another feature, the above-mentioned deflector is made from a non-ferrous metal, such as aluminium, or from a ferrous material, or from a polymer material charged to be rendered semi-conductive. 30 4 According to another feature, the above-mentioned sleeve extends over at least a part of the bar, said part being situated outside said deflector so as to achieve at least partial sleeving of said bar. 5 According to another feature, the above-mentioned flexible material is an elastomer or a TPE, for example silicon or EPDM. According to another feature, said apparatus is a medium-voltage electrical switch. 10 But other advantages and features of the invention will become more clearly apparent from the following detailed description which refers to the appended drawings given for example purposes only and in which: -Figure 1 is a partial view, in axial cross-section, of a connection device according to the 15 invention, according to a first embodiment comprising a plug, -Figure 2 is an identical view to that of the previous figure, according to a second embodiment comprising a capacitor designed for indicating presence/absence of voltage, 20 -Figure 3 is an identical view to that of the previous figure, according to a third embodiment of the invention comprising a capacitive divider, and -Figure 4 is an identical view to that of the previous figure, according to a fourth embodiment comprising a resistive divider. 25 An electrical connection device D according to the invention has been represented in the figures, fitted on a bushing I belonging to a medium- or high-voltage electrical switch so as perform electrical connection between a bar 2 and an insert 3 situated inside this bushing I. 30 This bushing t comprises a part of substantially conical shape i a the smallest diameter of which is located on the same side as the connection device D, this conical part being terminated at its base by a flared part Ib, this part being connected to a cylindrical part Ic 5 the diameter of which corresponds substantially to that of the free end le of the above mentioned conical part. Inside this bushing 1 there is located a metal insert 3 of cylindrical shape the axis X whereof is the same as the axis of the bushing, this insert extending slightly beyond the 5 bushing on the connection device side and being surrounded by an insulating part Id. The end part 2a of the bar 2 is designed to be electrically connected on this insert. This end part 2a is flattened and is connected to the main portion of bar of circular cross-section 2b by a conical part 2c. This bar will preferably be cylindrical but will be able to present other shapes, This bar can further be solid or hollow. 10 This device also comprises a deflector 4 forming a conductive shield, placed around the connection area 5. This deflector 4 presents a conical external shape flared in the direction of the bushing 1. It is formed by a first part 4a of substantially annular shape followed by a part in the form of a disc 4b followed by another part 4c of substantially annular shape of reduced thickness compared with the first part. 15 According to the invention, this deflector 4 is moulded from casting by a flexible material over substantially the whole of its external surface thereby forming a sleeve 6 of substantially cylindrical shape comprising at its base a part 6a designed to press on the conical surface I a of the bushing, and comprising at its top part a part 6b folded in rounded manner in the direction of the axis Y of the sleeve 6, and then in the direction of the 20 apparatus so as to form a tubular hole 7. Likewise, the sleeve 6 comprises a part of reduced thickness 8 running up along the inside surface of the above-mentioned annular second part 4c of the deflector, thereby creating a space 9 between this elastomer part 8 and the connection area 5 for a gas to be inlet therein. The device also comprises means for fixing the deflector 4 onto the bar, said means 25 comprising a screw 10 designed to pass through two facing holes respectively belonging to the deflector 4 and to the bar 2 and designed to be screwed into a threaded bore 10b formed in said insert 3, the base of the screw head 10a being pressing on the deflector 4 by means of a washer, and the bar 2 being fitted between the deflector 4 and insert 3. According to the invention, the pressure applied by the sleeve 6 on the bushing 1 is exerted 30 by the deflector 4 being made from a relatively rigid material. This deflector should preferably be made from a non-ferrous metal such as aluminium, or a ferrous metal, but it could also be made from a polymer material charged to be rendered semi-conductive.

6 The sleeve 6 also comprises a part 6c extending on the bar so as to perform sleeving of the bar and designed to improve the dielectric characteristics of the connection device and complete the dielectric tightness of the sleeving device along the bars. According to the embodiment of figure 1, a plug 11 is inserted in the tubular hole 7 of the 5 device, this plug being designed to mask access to the electrical connection. According to another embodiment illustrated in figure 2, a capacitor designed to participate in indication of the presence or absence of voltage is inserted in this hole 7. According to another embodiment illustrated in figure 3, a capacitive divider 13 according to another embodiment is also inserted in this hole for the purposes of performing voltage 10 measurement. In figure 4, a resistive divider 14 is inserted in this hole to perform this measurement. All these devices are secured by clip-fastening in said tubular hole 7. The clip-fastening means comprise a thickened part 15 of the flexible material moulded from casting, situated at the top part of the tubular hole 7, this thickened part being followed by a part 16 of 15 regularly reduced thickness down to the bottom of the hole. These variations of thickness collaborate with the shape of the parts of the inserted devices to achieve clip-fastening of the device in said hole. Other clip-fastening means can be envisaged. 20 A connection device whereby the ageing resistance is improved from the dielectric standpoint in difficult environments of the busbar has thereby been achieved according to the invention by constituting a sleeving not requiring a particular profile for the connecting bushings or outputs of any enclosure containing a medium- or high-voltage switchgear apparatus. The manufacturing moulds of existing parts therefore do not have to be 25 modified, and compact shapes can be preserved. Shielding of the pointed shapes of the conductors, and therefore distribution of the electrical field, is ensured by a conductive deflector-shield at the same potential as the busbar and moulded from casting in a flexible material (elastomer or TPE, for example 30 silicon, EPDM, etc). The invention is based on the fact that this shield is moulded from casting thereby enabling the latter to provide an enhanced dielectric tightness on any bushing shape, said shield 7 performing its shielding function perfectly as its external surface is contained in a solid insulator with the absence of gas between the flexible material and the deflector. This moulding from casting also prevents the presence of polluting agents at the triple point while at the same time almost eliminating the gas. 5 In the illustrated embodiments, the bushings present shapes resembling those of the insulators and comprise fins, However, the principle of the invention can apply to other shapes enabling a moulded from casting deflector to increase the pressures exerted so as to ensure an enhanced tightness between the flexible material and the bushing. On account of the presence of this deflector, 10 a higher pressure is exerted on the bushing, this pressure of the elastomer material on the harder material of the enclosure being directed in such a way as to be exerted over the whole of the circumference of the sleeve. The deflector therefore enables this pressure to be applied uniformly over the whole of the circumference of the bushing, This sleeve also enables the calories generated at the level of the electrical contact to be 15 removed, in particular when it is made from metal material, Care must then be taken to choose moulding materials with good emissivity coefficients at infrared frequencies. It should be noted that deformation of the sleeve is achieved when assembly of the device is performed, the pressure ensuring tightness being provided by the rigidity of the shield. The deflector enables the add-on devices, such as the plug, capacitive divider, resistive 20 divider or a capacitor, to be securedly held in a closed position. The principle of this sleeve thereby facilitates installation of these devices, which devices could even be installed live by means of tooling guaranteeing operator safety, without it being necessary to perform prior disassembly of other elements. 25 The present invention is not limited to the described and illustrated embodiments which have been given for example purposes only. On the contrary, the invention extends to encompass all the technical equivalents of the means described as well as combinations thereof provided the latter are performed 30 according to the spirit of the invention.

Claims

1. A device for electrical connection of at least one bar belonging to a busbar to an 5 electrical bushing belonging to the insulating enclosure of an electrical switchgear apparatus, said bushing comprising a conductive insert at least partially surrounded by an insulating part, said device comprising means for making electrical connection between an end part of the bar and said conductive insert, and a deflector formed by a conductive shield designed to be electrically connected to the bar and placed around the electrical 10 connection area between the bar and said insert, said deflector (4) being moulded from casting in a flexible material, said material forming a sleeve (6) of substantially cylindrical shape that is able, due to the effect of the rigidity of said deflector (4), to press via its end part situated on the same side as the apparatus on the above-mentioned insulating part (1d) of the bushing (I) presenting a complementary shape, with a certain pressure so as to 15 achieve perfect tightness between said flexible material and the insulating part of the bushing (I), so as to ensure an enhanced dielectric tightness over substantially the whole of the circumference of the above-mentioned bottom part of the sleeve (6), the external surface of the deflector (4) being substantially totally coated by the flexible material, said material constituting a solid insulator, with an absence of gas between the deflector (4) and 20 the material, so as to enhance the efficiency of the deflector-shield (4), that the above mentioned deflector (4) presents a substantially conical external shape the part whereof having the largest diameter being located towards the inside of the apparatus, said deflector comprising a first part (4a) of annular shape situated on the outside of the apparatus followed by a second part (4b) in the form of a disc, said second part being followed by a 25 third part (4c) of annular shape of reduced thickness compared with the thickness of the first part and situated on the same side as the apparatus, the above-mentioned connection means comprising a screw (10) and a threaded bore (10b) formed in the insert (3), the second part (4b) of the deflector, in the form of a disc, and the end (2a) of the bar respectively comprising two facing holes designed for the above-mentioned fixing screw 30 (10) to pass through, the screw head (10 a) being designed to press on said second part (4b) of the deflector, after the screw has been screwed into the insert, the deflector being fitted between the screw head (10a) and the end part (2a) of the bar, which end part being 9 pressing on the end part of the insert (3), the edge of the top part (6b) of the sleeve (6) being folded towards the axis Y of the sleeve and then towards the inside of the apparatus along the surface of the deflector (4) so as to form a tubular hole (7) for the screw head (lOa) to pass through. 5

2. The device for electrical connection according to claim 1, characterized in that the insulating part (Id) of the bushing (1) comprises a part of conical shape (la) and a part of flared shape (1b) on the same side as the apparatus. 10

3. The device for electrical connection according to claim 1 or 2, characterized in that it comprises a plug (11), a resistive divider (14), a capacitive divider (12,13) or a capacitor designed to participate in indicating the presence or absence of voltage, designed to be fitted inside the above-mentioned tubular hole (7). 15

4. The device for electrical connection according to claim 3, characterized in that the plug (11), resistive divider (14), capacitive divider (12,13) or capacitor is fixed by clip fastening means inside said hole (7).

5. The device for electrical connection according to claim 4, characterized in that the 20 above-mentioned clip-fastening means comprise a part of increased thickness (15) provided at the end of the sleeve (6b) situated on the outside of the apparatus, followed by a part of regularly thinned thickness (16) situated inside the tubular hole (7).

6. The device for electrical connection according to any one of the foregoing claims, 25 characterized in that the above-mentioned deflector (4) is made from a non-ferrous metal, such as aluminium, or from a ferrous material, or from a polymer material charged to be rendered semi-conductive,

7. The device for electrical connection according to any one of the foregoing claims, 30 characterized in that the above-mentioned sleeve (6) is extended over at least a part of the bar (2), said part being situated outside said deflector so as to perform at least partial sleeving of said bar. 10

8. The device for electrical connection according to any one of the foregoing claims, characterized in that the above-mentioned flexible material is an elastomer or a TPE, for example silicon or EPDM, 5

9. The device for electrical connection according to any one of the foregoing claims, characterized in that said apparatus is a medium-voltage electrical switch.