CABLE CONNECTOR

Abstract: A high voltage adaptor (2) for connecting a cable (20) to a transformer bushing (40) has, in addition to a socket for a closure or inspection plug (36), a socket (10) arranged to receive a surge arrester (26). The surge arrester (26) and cable (20) are electrically connected together and to the bushing (40) within the insulating body.

Description: DESCRIPTION CABLE CONNECTOR This invention relates to a cable connector, and in par¬ ticular to a connector for interconnecting a high voltage electric power cable with high voltage apparatus, such as a transformer or switchgear. By 'high voltage' is meant a voltage in excess of lkV, and may typically be in the range lOkV to 36kV. Cable connectors suitable for this purpose are disclosed in EP-A-0225190 and EP-A-0139483 the entire contents of which are included herein by this reference. There is disclosed in EP-A-0225190 a cable connection arrangement in which an end of the cable is fully terminated and the con¬ nector is arranged to receive the terminated cable as a push- fit therein. A terminal then secures a conductive lug of the terminated cable to a contact member retained within the insulating body of the connector. The connector of EP-A-0139483 in addition to having the electrical contact member completely contained within the insulating body, receives the cable end, which need not be completely ter¬ minated, within a passageway that is heat-recoverable. It is an object of the present invention to provide an improved cable connector. In accordance with one aspect of the present invention, there is provided a high voltage cable connector comprising an electrically insulating and substantially non-tracking body having four sockets extending thereinto; wherein a first of the sockets is arranged to receive a bushing of high voltage electrical apparatus, a second of the sockets is arranged to recieve a plug, a third of the sockets is arranged to receive one end of a high voltage electric power cable, and a fourth of the sockets is arranged to receive a surge arrester; wherein the third and fourth sockets open into one another whereby the one end of the cable and one end of the surge arrester can be electrically connected together; within the insulating body and wherein the third and fourth sockets open into the second socket thereby in the absence of the plug to allow access through the second socket to said one ends of the cable and surge arrester for connection to each other and, in operation, to a terminal of the bushing of the electrical apparatus. It is becoming increasingly desirable to provide protec¬ tion for high voltage systems against overvoltage surges due, for example, to a short circuit or a lightning strike, and surge arresters (or surge diverters) are employed to do this. Surge arresters are normally non-conductive, but their rating is selected for a given high voltage system such that on occurrence of a voltage above a given value they become conductive and safely conduct fault current to earth before any damage is done to the system. The surge arrester then returns to its non-conductive state. The operative component of a surge arrester may comprise a non¬ linear resistor arrangement formed from a plurality, that its to say two or more, of metal oxide, for example zinc oxide, varistor blocks stacked end-to-end, having a plate or other conductive member at each end to form a pair of electrodes. The resistor and electrode arrangement is mounted within and retained by a housing, which may be formed from a non-tracking insulating polymeric material or from porcelain. By 'non-tracking' material is meant a material that is resistant to the formation of carbonaceous paths therealong, and that satisfies the requirements of the ASTM D 2303 Inclined Plane test. The outer surface of the surge arrester may be convoluted and/or may of shedded con¬ figuration for enhanced electrical performance, particularly in adverse environmental conditions of salt, acids and humi¬ dity. The present invention thus provides overvoltage pro¬ tection for a high voltage system in a particularly convenient manner by combining the features of cable connec¬ tor and surge arrester in a single compact unit. Preferably the insulating body of the connector contains a electric contact means that is arranged in operation, that is to say when a cable and a surge arrester are mounted in the connector and the connector is mounted on the electrical apparatus, to provide electrical connection between, on the one hand, the terminal of the bushing of the apparatus and, on the other hand, the said one end of the cable and of the surge arrester. Conveniently, the contact means may comprise a first elongate portion, which may be a pin or a socket, that extends into the first socket, a second elongate portion that extends into the second socket, and an intermediate portion that is mechanically retained by the insulating body of the connector. Preferably the first and second elongate portions extend freely into their respective sockets, i.e. without contacting the walls of those sockets, and advantageously they are aligned axially therealong. The surge arrester and cable when fitted to the connector pre¬ ferably extend sealingly through their respective sockets in the insulating body and are connected to the second portion of the electrical contact member within the second socket. The plug is advantageously sealingly fitted into the second socket, and may receive, and mechanically support, the free end of the second portion of the contact member. The plug may be provided with a capacitive test point, accessible from outside the connector when the plug is mounted therein, for determination of voltage applied to the contact member. A particularly compact configuration of connector can be obtained when the first and second sockets are substantially axially aligned with one another, and the third and fourth sockets extend transversely thereof substantially in the same plane and to the same side of the first and second sockets. The distance between the bushing of the electrical apparatus and the plug can thus be minimised whilst not only allowing for connection of the cable but also allowing for the presence of the surge arrester. Such a configuration is particularly useful when the connector, and particularly three adjacent connectors of a three-phase system, need to be mounted within a cabinet which either needs to be as small as possible or is an existing cabinet that was not originally designed for a system incorporating a surge arrester. The fitting of the cable into the connector may be as disclosed in EP-A-0225190 or as in EP-A-0139483. Using the former arrangement, one end of the electric cable extends sealingly into the insulating body through the third socket, an outer insulating jacket of the cable has been removed to expose an electrical screen of the cable, the screen has been removed to expose primary insulation of the cable, and the primary insulation has been removed to expose a conduc¬ tor of the cable, and the cable is terminated by electrical stress control material that extends over the exposed end of the screen and along at least part of the exposed primary insulation, and by electrical insualtion material that extends in close conformity over the cable screen and over the stress control material. In general, the sockets, but particularly the third and/or fourth sockets, may be arranged to receive the asso¬ ciated component as a push fit therein. In an alternative arrangement, one or more of the sockets, and in particular the third and/or fourth socket, may be recoverable, pre¬ ferably by the application of heat thereto, in order to achieve sealing conformity with the associated component. An example of heat sealing a cable into a connector is shown in EP-A-0139483. Although the entire surge arrester apart from its earthing terminal, may be enclosed within the fourth socket, it is envisaged that the body of the surge arrester may remain outside the connector and that a terminal extending from one end will be introduced through the fourth socket to make the required electrical connection. A connector in accordance with the present invention will now be described, by way of example, with reference to the accompanying drawing, in which Figure l shows the connector in sectional elevation with a calbe and surge arrester mounted therein; and Figure 2 shows as detail of a connection lug. Referring to the drawing, the connector has an insu¬ lating non-tracking body 2 of plastics material, such as EPDM. The body 2 has a first socket 4 that is of inwardly tapering and frusto-conical configuration. A second socket 6 of the body 2 has the same configuration and is axially aligned with the socket 4. A third socket 8, of circular section, leads into the connector body 2 perpendicularly to the sockets 4 and 6 and opens into the second socket 6. A fourth socket 10, of circular section, also leads into the connector body 2 perpendicularly to the first and second sockets 4 and 6, in the same plane and extending in the same general direction as the socket 8. An annular metal contact disc 12, for example of brass or copper, is retained in a recess of the insulating body 2 at the junction of the first and second sockets 4, 6 and threadedly receives a conductive contact pin 14 therein such that a first portion 16 of the pin extends axially into the first socket 4 and a second portion 18 of the pin extends into the second socket 6. A 15kV cable 20 that has been completely terminated and that has an outer sleeve 22 of heat-recoverable insulating, non-tracking polymeric tubing thereon and a metal connecting lug 24 (see also Figure 2) at the end thereof is sealingly inserted as a push-fit into the socket 8 so as to dispose the lug 24 around the contact pin 14 adjacent the contact- disc 12. The lug 24 is then secured in position by means of a nut 25 and a spring washer, access to do this being obtained via the socket 6. A surge arrester 26 has an insulating, non-tracking housing 28, and is terminated at one end by an insulated rod 30 having a connecting lug 32 (see also Figure 2) at the free end thereof, and at the other end by an earthing stud 35. The rod 30 is sealingly inserted as a push-fit into the socket 10 so as to dispose the lug 32 around the contact pin 14 adjacent the cable locking nut 25. The lug 32 is then secured in position by a further nut 34 and a spring washer. A back plug 36 of insulating plastics material is then sealingly inserted as a push-fit into the socket 6. The plug 36 has a metal insert 38 that slidably receives the free end of the second portion 18 of the contact pin 14. Thus, the pin 14 with the cable and surge arrester lugs 24,32 secured thereto is firmly mounted in the connector at two positions along its length. The connector body 2 is mounted on electrical apparatus (not shown) such as a transformer or switchgear by having an insulating bushing 40 of the apparatus sealingly inserted as a push-fit into the socket 4. This action causes the first portion 16 of the contact pin 14 to engage with a conductive terminal 42 of the electrical apparatus that extends through the bushing 40. As can be seen from Figure 1, with the insulating con¬ nector body 2, the cable 20, and the surge arrester 26 lying substantially in the same plane, and with the surge arrester 26 extending longitudinally beyond the back plug 36 by only a comparatively small amount, a very compact arrangement is obtained, that can conveniently be mounted within the con¬ fines of existing cabinets for cable terminations. It will be clear that should any significant overvoltage appear on the terminal 42 of the electrical apparatus or on the conductor of the cable 20 (connected to its lug 24), the resulting current will be short-circuitted through the surge arrester 26 to earth at its stud 35.

Claims: CLAIMS 1. A high voltage cable connector comprising an electri¬ cally insulating and substantially non-tracking body having four sockets extending thereinto; wherein a first of the sockets is arranged to receive a bushing of high voltage electrical apparatus, a second of the sockets is arranged to receive a plug, a third of the sockets is arranged to receive one end of a high voltage electric power cable, and a fourth of the sockets is arranged to receive a surge arrester; wherein the third and fourth sockets open into one another whereby the one end of the cable and one end of the surge arrester can be electrically connected together within the insulating body; and wherein the third and fourth sockets open into the second socket thereby in the absence of the plug to allow access through the second socket to said one ends of the cable and surge arrester for connection to each other and, in operation, to a terminal of the bushing of the electri¬ cal apparatus. 2. A connector according to claim 1, comprising electrical contact means mounted in the insulating body thereof, the contact means being arranged, in operation, to make electrical contact with the terminal of the bushing of the electrical apparatus and said one end of the cable and of the surge arrester. 3. A connector according to claim 2, wherein the electri¬ cal contact means comprises a first elongate portion that extends freely into the first socket, a second elongate portion that extends freely into the second socket and an intermediate portion that is mechanically retained by the insulating body of the connector. 4. A connector according to claim 2 or claim 3, comprising a surge arrester, wherein one end of the surge arrester extends sealingly into the insulating body through the fourth socket and is connected to electrical contact means. 5. A connector according to any one of claims 2 to 4, wherein one end of an electric cable extends sealingly into the insulating body through the third socket and is connected to electrical contact means. 6. A connector according to any of claims 2 to 5, comprising a plug that is sealingly inserted in the second socket and that receives an end of the electri¬ cal contact means. 7. A connector according to any preceding claim, wherein the first and second sockets are substantially axially aligned with one another, and wherein the third and fourth sockets extend transversely thereof substan¬ tially in the same plane. 8. A connector according to any preceding claim wherein the third and/or fourth sockets are arranged to receive the cable or surge arrester respectively as a push-fit therein. 9. A connector according to claim 8, wherein one end of an electric cable extends sealingly into the insulating body through the third socket; wherein an outer insu¬ lating jacket of the cable has been removed to expose an electrical screen of the cable, the screen has been removed to expose primary insulation of the cable, and the primary insulation has been removed to expose a conductor of the cable; wherein the cable is terminated by electrical stress control material that extends over the exposed end of the screen and along at least part of the exposed primary insulation, and by electrical insulation material that extends in close conformity over the cable screen and over the stress control material; and wherein the third socket is arranged to receive the terminated cable as a push-fit therein. 10. A connector according to any one of claims 1 to 7, wherein the third and/or fourth sockets are reco¬ verable, preferably by heat, on to the cable or surge arrester respectively.

Inventors: MIKLI NORBERT, MIKLI, NORBERT
Applicants: RAYCHEM GMBH, RAYCHEM LTD, RAYCHEM LIMITED
Application year: 1990
Main classification: H01R13
IPC codes: H01R13