Electric connection

Details Electric connection Electric connection

1999-09-22

2001-05-08

Bradley, Paula (Department: 2833)

Electrical connectors

Electromagnetic or electrostatic shield

Shielding individually surrounding or interposed between...

C439S186000

Reexamination Certificate

active

06227908

ABSTRACT:

This invention relates to electrical connections and in particular to an electrical interconnection arrangement for making an electrical connection between at least one electrical cable and another piece of electrical equipment, which may be another cable, or may be a bushing of electrical switchgear or a transformer, for example.
The invention is particularly advantageous for use at rated voltages of 1 kV and above, and where the equipment is electrically screened. Furthermore, when used for connecting cables together, the invention is particularly advantageous for the formation of branch joints, but is also applicable to in-line joints.
Notwithstanding the above, and for ease of exemplification only, the invention will be further described mainly with reference to the formation of a branch joint.
Arrangements for forming branch joints are many and varied. EP-B-0070696 discloses a simple cable jointing connector comprising a solid electrically insulating body that encloses a plurality of bus bar conductors whose extremities project therefrom within extension insulators, for connection to conductors of cores of respective cables. Each connection is made by bolting a lug of the cable conductor to the extremity of the bus bar, and is then insulated by a sleeve, that is preferably heat shrinkable. The cables are physically isolated from each other, so that interconnection can be made between cables that would otherwise not be compatible physically and/or chemically, for example by being of different size, configuration or material. In this context it is mentioned that one common type of cable (paper-lead) is oil-filled and another (polymeric) has material that is susceptible to damage when contacted by oil. A disadvantage of this connector is that it is not electrically screened. Furthermore, when heat-shrinkable insulating sleeves are used to insulate the connection to the cables, disconnection can be inconvenient, and cannot be made without destroying at least part of the original connection.
U.S. Pat. No. 3,961,127 also discloses a universal power cable joint for use with power cables having various insulations, and thus has the versatility of the connection of EP-B-0 070696. However, this joint is much more complex, and relies on gasket seals to ensure chemical separation between the cables. Although disconnection can be effected without actual destruction of any components, the entire joint must be disassembled. Also, this joint does not provide a screened arrangement.
When installing an electric cable of a power distribution system, as well as the necessity usually for in-line joints, it is often necessary to install or to make provision for subsequent installation of a branch joint or service joint. A service joint is to be regarded as a particular form of branch joint, in which the service cable is of lower capacity than the main cable. It is thus especially advantageous to be able to make provision for adding one or more branch cables subsequent to the installation of the main cable. EP-B-0253670 discloses a suitable connector for doing this, and whilst having the advantage of simplicity and ease of re-entry and of addition of further branch cables, does not provide for screening of the connection.
It is to be appreciated that the need for screening of cables, and thus of connection therebetween, becomes more important at higher voltages, especially at rated voltages of about b
6
kV and above, where touching the exterior of an insulated but unscreened cable can at least be unpleasant even if not dangerous. A connector that is screened, and that can be used with, i.e. electrically connected to, screened cables, is thus more versatile than one that is not.
It is one object of the present invention, to provide an electrical interconnection arrangement that is electrically screened, or shielded, that can be used with cables of various constructions, sizes and configurations, that is relatively easy to assemble and that can conveniently be disassembled if necessary.
In accordance with a first aspect of the present invention, there is provided an electrical interconnection arrangement for connecting together two pieces of electrical equipment, at least one of which may be an electrical cable, comprising: (a) a first connection component comprising a first elongate conductive member, which in use is at a relatively high voltage, enclosed within insulating material and protruding at one end beyond an end surface thereof, the other end of the first member being arranged for electrical connection with one of the pieces of electrical equipment, wherein said one end of the first conductive member has an enlarged radiussed region within the insulating material adjacent the protruding portion, thereby to provide electrical stress relief at the exposed surface of the insulating material, and (b) a second connection component comprising a second elongate conductive member enclosed within insulating material and having a socket exposed at an end surface thereof for receiving the protruding end of the first conductive member, the other end of the second member being arranged for electrical connection with the other of the pieces of electrical equipment; wherein a respective conductive layer extends over the surface of the insulating material of each connection component at its said one end and extends therealong towards its other end, thereby to provide electrical screening, which in use is substantially at earth potential, at said one end region of the component, each conductive layer terminating in respective first and second connection portions at respective one ends.
Thus, when the first and second conductive members interengage, to produce high voltage electrical interconnection between the two pieces of electrical equipment, the first and second connection portions also interengage, and can be secured together if necessary, to provide earthed electrical screening of the interconnection. Advantageously, the conductive members are, directly or indirectly, exposed at their other ends, proximate the electrical equipment beyond their respective insulating material and are electrically connected tO the conductive layers by electrical stress control arrangements, such as a layer of material, preferably polymeric, having stress control characteristics.
In this aspect, the invention is particularly suitable for forming an in-line connection between two cables, but it may also be used, for example, in connecting one cable to a bushing.
The invention is however also suitable for more versatile applications.
Thus, in accordance with a second aspect of the present invention, there is provided an electrical interconnection arrangement comprising: (a) a first, elongate, connection component comprising (i) a conductive member enclosed within insulating material and protruding from one end thereof, the other end being arranged for electrical connection to a conductor of a first piece of electrical equipment, for example, an electric cable, and (ii) a conductive layer extending over the surface of the insulating material at said one end and extending therealong towards the other end, thereby to provide electrical screening at one end region of the component, said conductive layer terminating in a connection portion at said one end; and (b) a second connection component comprising a body of electrically insulating material enclosing (i) an electrically conductive socket arranged to be electrically connected to other electrical equipment, and to receive and make electrical connection with the protruding end of the conductive member of the first connection component, and (ii) an electrically conductive structure located within the insulating body, spaced from and encircling the socket within and at a surface of the insulating body to provide an external connection portion, whereby on insertion of the conductive member of the first connection component into the socket of the second conduction component so as, in use, electrically to interconnect the electric cable to the other electrical equipment, th

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