ELECTRICAL CONNECTOR

Abstract: A connector (30) for connecting a high voltage cable by means of a terminal (38) to a transformer whose terminal bushing is received in a socket (32) employs a plug member (2) to effect the electrical and mechanical interconnection therebetween. The plug member (2) is formed from two parts (4, 6) that are releasably interengageable by means of a bayonet connection (16, 22). When interengaged, the plug member (2) is screwed into the connector so as to connect the cable via the terminal (38) to the bushing of the transformer. a slight rotation of the outer part (6) of the plug member (2) disengages it from the inner part (4) and allows it to be withdrawn from the connector (30) without disturbing the electrical and mechanical interconnection provided by the inner part (4). Furthermore, on such removal of the outer part (6), a terminal (14) of the inner part (4) can be accessed for sampling the voltage of the cable/transformer.

Description: ELECTRICAL CONNECTOR This invention relates to electrical connection between two pieces of electrical equipment, especially high voltage equipment. By high voltage is meant a voltage in excess of I V, and generally in excess of lOkV, and the electrical equipment may comprise a high voltage electric cable, a transformer or switchgear for example EP-A-0147979, the entire contents of which are included herein by this reference, discloses a high voltage connector that is suitable for use as a ring distribution unit, whereby electrical interconnection may be made or broken between a high voltage cable and a transformer without disturbing the mechanical interconnection between these two pieces of equipment. This is achieved by means of a tapered elongate continuity plug member that cooperates with a complementarily-shaped socket of an insulating body of the connector and that has two electrical contact portions spaced apart therealong. The cable and the transformer are mechanically and electrically connected to the connector at locations spaced apart along the socket so that without the continuity plug member in position they are electrically isolated from each other; the insulation there between can be enhanced by introducing a fully insulating plug into the socket. Insertion of the continuity plug member then serves electrically to interconnect the cable and transformer. At the outer end of the or each plug member, a capacitive test point may be located so that an operator can use a suitable probe to determine whether the equipment connected to the connector is live or is earthed. However, in some cir¬ cumstances such an indirect testing method is insufficient or unacceptable, and it is necessary to obtain direct access to a metal component connected to one or both of the pieces of equipment to determine or confirm its electrical status. Such direct access can be obtained with a conventional con¬ nector, such as disclosed in EP-A-0087267, in which an insu¬ lating sealing plug covers a metal contact stud that secures the two pieces of electrical equipment physically in contact with one another. However, that plug forms no part in making the electrical connection between the two pieces of electrical equipment, which is made by the metal stud, since the plug is arranged to be inserted only after the electri¬ cal connection has been made. It is one object of the pre¬ sent invention to provide a plug member, and a connection arrangement, that is an improvement on that described in above-mentioned EP-A-01 7979. It is a further object of the present invention to- pro¬ vide an electrical connector and a plug member therefor that not only allows electrical connection between two pieces of electrical equipment to be made and broken without disturbing the physical interconnection therebetween, but that also allows direct access to the high voltage terminal of at least one of the pieces of equipment without disturbing the mechanical or the electrical connection there between. In accordance with one aspect of the present invention, there is provided a plug member for sealingly engaging a complementarily-shaped socket of a high voltage connector that is suitable for electrically interconnecting two pieces of electrical equipment, the plug member comprising an inner part having a contact portion arranged in use to make direct mechanical and electrical contact with at least one of said pieces of electrical equipment and an outer insulating part that is mechanically interengageable with the inner part such that movement of the outer part in one sense is arranged to engage the inner part and urge it into the socket of the connector to effect said at least one contact, and such that subsequent movement of the outer part in another sense is arranged to disengage said two parts from one another thereby to allow removal only of said outer part from the connector and to expose said contact portion of the inner part. In accordance with another aspect of the present inven¬ tion, there is provided a high voltage connector suitable for interconnecting two pieces of electrical equipment, the connector comprising a socket in an insulating body portion thereof and a complementarily-shaped plug member in accor¬ dance with the said one aspect of the invention, whereby the plug member forms a sealing engagement along substantially it entire lenght with the socket. Preferably the features of the plug member, and of the connection arrangement, of the present invention are com¬ bined with those of above mentioned EP-A-0147979. The plug member may be of generally elongate shape and the inner and outer parts thereof may extend generally longitudinally of each other. The two parts may be interengaged and disengaged by a rotary movement about the longitudinal axis of the plug member, and the two interlocked parts may be push-fitted as a tight fit into the socket, optionally with a further rotary movement in the same, interlocking sense. Rotary movement in the opposite sense for example may then be arranged to separate the two parts for exposure of the contact portion of the inner part so as to allow access thereto by a probe from outside the connector. Advantageously, the interengage ent of the two parts of the plug member is effected by a bayonet-type coupling, that is to say a coupling that involves a slight rotation to disengage the two parts so that one can be removed subsequently by a linear pulling action. In any event, it is preferred that engagement and disengagement of the two parts of the plug member should involve a relative rotation therebetween of not more than about one revolution. A coupling of this form not only allows quick and easy disengagement, but also minimises any disturbance of the electrical interconnection with the equipment. Thus, for example by screwing the plug member into the socket of the connector, the plug member can provide electrical continuity between the two pieces of electrical equipment in the manner described in above-mentioned EP-A-0147979. In this embodiment of the invention, unscrewing of the outer part of the plug member causes its disengagement from the inner part. This action is arranged to expose the contact portion of the plug member, which is associated with the inner part, whilst due to the fact that the inner part remains in position, the electrical connec¬ tion between the two pieces of electrical equipment is not disturbed. A probe can then be placed on to the exposed contact portion to determine whether or not the electrical equipment is live. It is envisaged that the interengagement of the two parts of the plug member may also be arranged so that move¬ ment of the outer part in a further sense allows removal of both the inner and outer parts as a single unit. For example a longitudinal pulling or pushing action on the outer part may be arranged to lock the two parts together, for example by temporarily locking the bayonet coupling, such that a subsequent rotation of the outer part to withdraw it from the connector also results in the inner part being withdrawn as the same time. Such an additional interconnection between the two parts may be useful when it is known from other means that there is no power applied to the pieces of electrical equipment that are interconnected. Such other means may comprise a capacitive indicator, sensor or testing point located on the outer part of the plug member and accessible from outside the connector when the plug member is mounted therein. Such means may comprise for example a metal lug or a socket in the exposed surface of the outer part used for removal of the outer part from the connector. In some circumstances therefore, it may be acceptable to use the two part plug member in effect as an integral plug member; by checking the voltage due to capaci¬ tive connection between the exposed point and the interior of the connector, an operator can determine whether or not the equipment is live, and if he is satisfied that it is not then he can move the outer part of the plug member in such a way that the inner part is removed from the connector at the same time. If the operator is not so satisfied, or if the operating conditions are such that dependence on a capaci¬ tive indication may not be relied upon, then the operator can move the outer part such that the inner part remains in position, thereby allowing direct electrical contact to determine whether or not voltage is applied to the equipment. Due to the type of interengage ent between the two parts of the plug member, a specially designed tool may be required to remove the inner part, and conveniently the exposed surface of the outer part can be arranged to accept the same tool. Thus, the same tool can be arranged so as to allow it to remove first the outer part and then the inner part. Preferably, when the two parts of the plug member are arranged to be capable of being removed as an integral unit, the same tool is arranged to be able to accomplish this. The plug member of the present invention instead of being a continuity plug may be a further plug, as described in EP-A-0147979, that is arranged to make electrical contact with one or the other only of the two pieces of electrical equipment. In accordance with a still further aspect of the pre¬ sent invention, there is provided a method of making and breaking an electrical connection between two pieces of electrical equipment; wherein an insulating body of a con¬ nector has two sockets therein for receiving respective ones of said pieces of electrical equipment; and wherein a plug member is arranged to be inserted into a further socket of the insulating body thereby electrically to interconnect the two pieces of electrical equipment; wherein the plug member comprises (1) an inner part having a contact portion arranged in use to make direct mechanical and electrical contact with at least one of said pieces of electrical equipment, and (2) an outer part that is insulating and mechanically interengageable with the inner part; the method comprising the steps of interengaging the two parts of the plug member, inserting the interengaged plug member into the further socket of the connector and moving the outer part of the plug member in one sense so as to make electrical con¬ nection between the plug member and the electrical equip¬ ment, and subsequently moving the outer part of the plug member in another sense so as to disengage the two parts from one another and to remove the outer part from the con¬ nector whilst maintaining the electrical connection. It is to be understood that the connector and plug member used in the method of the invention may be as herein¬ before described, and that the method may involve other steps as herein described. A plug member and connector each in accordance with the present invention, will now be described, by way of example, with reference to the accompanying drawings, in which:- Figure l shows the plug member partially in section with the two parts thereof disengaged from one another; Figure 2 shows the connector with the plug member of Figure 1 fully engaged therewith; and Figure 3 shows the connector of Figure 2 with the outer part of the plug member removed. Referring to Figure 1, the elongate generally cylindri¬ cal tapered plug member 2 comprises an inner part 4 and an outer part 6. The inner part 4 has a metal contact portion 8 embedded in insulating material 10. The contact portion 8 extends from the insulation 10 to terminate in metal studs 12 and 14 at the innermost and outermost ends respectively of the plug part 4. The outer stud 12 has a cylindrical pin 16, that forms one part of a bayonet coupling, extending transversely therethrough partway along its shank and ends in a hexagonal outer surface. The outer part 6 has an insu¬ lating body 18 having a metal cup-shaped receptacle 20 embedded therein. The receptacle 20 forms the other part of the bayonet coupling and to this end has a curved track 22 cut-out of its wall to receive the pin 16 of the inner plug part 4. A metal lug 24 is embedded in the insulation 18 extending therefrom to be gripped by an operating stick, as described hereinafter. It will be appreciated that the lug 24 will be capacitively coupled to the receptacle 20. Referring to Figure 2, the connector 30 has a first socket 32 tapering thereinto from one side, and a second socket 34 tapering thereinto from an opposed side. In use, the bushing (not shown) of a transformer engages the first socket 32 and mates with the inner stud 12 of the plug member 2 at the location where the two sockets 32, 34 meet. An annular contact 36 extends around the second socket 34 partway along its length and extends via an embedded metal terminal 38 through the connector wall for connection to an electric cable (not shown). The plug member 2 is inserted into the socket 34 of the connector 30 by a combined pushing and screwing action operating on the lug 24. By rotating the lug 24 clockwise, the bayonet coupling between the two parts 4 and 6 of the plug member 2 is tightened and the entire plug can be urged into the connector 30 so as to dispose the inner stud 12 in the socket 32 for connection to the transformer and so that the annular connector contact 36 is engaged by an exposed cylindrical surface of the contact portion 8 of the inner plug member 4. Thus, the inner plug part 4 provides electrical interconnection between the transformer and the cable, each of which is independently mechanically secured to the connector 30, and the outer plug part 6 provides electrical insulation. Should an operator wish to determine whether or not power is being supplied to the cable, an operating stick can be applied to the lug 24 which can then be rotated in the opposite, anti-clockwise direction. This action will disengage the bayonet coupling between the pin 16 of the inner part 4 and the curved track 22 of the outer part 6 of the plug member 2, thus allowing the other part 6 to be withdrawn from the connector 30 whilst leaving the inner part 4 in place and the electrical connection between the transformer and cable intact. This situation is shown in Figure 3. As can be seen from Figure 3, the outer stud 14 of the inner plug member part 4 is now exposed and can be accessed from outside the connector 30 by a probe to ascer¬ tain whether or not voltage is applied thereto, and thus to the electrical equipment. After determining or ensuring that the equipment is earthed, an operating stick with a bayonet socket can be fitted on to the hexagonal end of the stud 14 and over the pin 16 to remove the inner part 4 of the plug member 2 from the socket 34 of the connector 30, and thus electrically to disengage the two pieces of electrical equipment from each other. Preliminary checking of the earthing of the equipment, if required, can conveniently be carried out before removal of the outer plug part by using the metal lug 24 as a capa¬ citive test point. The metal lug 24 may be replaced by a bayonet coupling corresponding to that of the stud 14 and pin 16, thus still serving as a preliminary capacitive test point and allowing the same operating stick to remove each of the plug parts. It is to be understood that the connector and plug member of the present invention may be such as to form a ring distribution unit, formed for example by the coupling together of three connectors such as those described herein with reference to Figure 2. Although the plug member of this invention finds par¬ ticularly suitable application as the plug member of the connector of EP-A-0147979, it is to be understood that its inventive features may be embodied in plug members for other connectors.

Claims: Claims 1. A high voltage connector suitable for interconnecting two pieces of electrical equipment, the connector comprising a socket in an insulating body portion thereof, and a complementarily-shaped plug member which is arranged to form a sealing engagement along substan¬ tially its entire length with the socket, wherein the plug member comprises (1) an inner part having a con¬ tact portion arranged in use to make direct mechanical and electrical contact with at least one of said pieces of electrical equipment, and (2) an outer part that is insulating and mechanically interengageable with the inner part such that, when interengaged, movement of the outer part in one sense is arranged to urge the inner part into the socket of the connector to effect said at least one contact, and such that subsequent movement of the outer part in another sense is arranged to disengage said two parts from one another thereby to allow removal only of said outer part from the connec¬ tor and to expose said contact portion of the inner part. 2. A connector according to claim 1, wherein the plug member is of generally elongate form, and wherein the inner and outer parts extend generally longitudinally of one another. 3. A connector according to claim 1 or claim 2, wherein at least one of said senses of movement comprises a rota¬ tional movement. 4. A connector according to claim 3, wherein each of the said senses of movement comprises a rotational move¬ ment, one being clockwise and the other being anti¬ clockwise. 5. A connector according to any one of the preceding claims, wherein movement of the outer part of the plug member in said another sense is a rotational movement such that the inner and outer parts of the plug member become disengaged by a relative rotation therebetween of less than one revolution. 6. A connector according to any one of the preceding claims, wherein said interengageability of the inner and outer parts of the plug member is by means of a bayonet coupling. 7. A connector according to any preceding claim, wherein movement of the outer part in a further sense is arranged to allow removal of both the inner and outer parts of the plug member simultaneously. 8. A connector according to any preceding claim, wherein the socket is of generally frusto-conical configuration tapering inwardly of the connector. 9. A connector according to any preceding claim, wherein said pieces of electrical equipment are electrically connected thereto at locations spaced apart along said socket. 10. A connector according to claim 9, wherein the plug member on engagement with the socket disposes its con¬ tact portion so as electrically to interconnect each of said pieces of equipment. 11. A connector according in any preceding claims, wherein the inner part of the plug member is arranged electri¬ cally to contact each of said pieces of electrical equipment at spaced apart locations within the insu¬ lating body of the connector. 12. A method of making and breaking electrical connection between two pieces of electrical equipment; wherein an insulating body of a connector has two sockets therein for receiving respective ones of siad pieces of electrical equipment; and wherein a plug member is arranged to be inserted into a further socket of the insulating body thereby electrically to interconnect the two pieces of electrical equipment; wherein the plug member comprises (1) an inner part having a contact portion arranged in use to make direct mechanical and electrical contact with at least one of said pieces of electrical equip¬ ment, and (2) an outer part that is insulating and mechanically interengageable with the inner part; the method comprising the steps of interengaging the two parts of the plug member, inserting the interengaged plug member into the further socket of the connector and moving the outer part of the plug member in one sense so as to make electrical connection between the plug member and the electrical equipment, and subsequently moving the outer part of the plug member in another sense so as to disengage the two parts from one another and to remove the outer part from the connector whilst maintaining the electrical connection.

Inventors: CLARKE GRAHAM, THORNLEY DAVID, CLARKE, GRAHAM, THORNLEY, DAVID
Applicants: RAYCHEM LTD, RAYCHEM LIMITED
Application year: 1990
Main classification: H01R13
IPC codes: H01R13