GB2288696A - Cable splice or termination - Google Patents

Abstract

An electrical cable splice has an outer housing (10) and an inner shell (9) with a bore in which the conductors (3,4) of two electrical cables are laid. Deformable electrically insulating plastics material such as a silicon rubber-based gel is included in the bore (11) of the shell (9) and arranged so that, when the parts of the shell (9) are closed around the conductors by the housing (10), the deformable plastics material exudes to fill any gap between the parts of the insulating shell. The housing is attached to cable entry components (13) each of which includes a compressible insulating disc (14). The cable screens (6) are joined via the components (13), the body (10) and an electro-deposited screening (15) on the outside of the shell (9). One of the cables may be replaced by a terminating component (not shown) which terminates the remaining cable. <IMAGE>

Description

ELECTRICAL JOINT ARRANGEMENT This invention relates to an electrical connector arrangement for electric cables. The arrangement is designed primarily for single conductor cables but it may equally be applied with modification to three phase or other multiple core cables. Principally the invention is intended for cables operating at a medium voltage within the range 6/10 Kv to 21/36 Kv.

However the invention is not limited to cables in this range and can be applied to other cables.

When it is required to make ajoint between two medium voltage cables it is necessary to dress the end of each cable and to apply a connector to the prepared conductors and then to re-insulate the joint and to cover the dressed ends so that there is a continuity of the electrical conductor and also of the insulation and any shielding. The type ofjoints previously used have been connectors which have the insulation applied over one end of the cable to be jointed and this is in the form of a sleeve which is slid back over the cable while the electrical conductor connector is made and after the connection is completed the sleeve is pulled to cover the connection and to provide insulation for it. A convenient way of applying the sleeve is to use a heat shrink sleeve which is of a plastics recoverable material which shrinks as soon as heat is applied to it. One of the problems with this type of jointing is that a large length of end of the cable has to be dressed to enable the sleeve to be slid over it and it is best if possible to keep the dressing down to a minimum length.

An alternative form of joint is to use in non-continuous tubular form of connector insulation, for example wrapped tapes, pitch or resinous material or combination thereof, but this form of joint is more prone to problems of misassembly because it requires a higher degree of craft skills.

It is an object of the present invention to provide an improved form of non-tubular joint for medium voltage cables.

According to the present invention, an electrical joint arrangement comprises an outer housing having an insulating inner tubular shell and the shell has a central bore in which the conductors of two electrical cables to be longitudinally jointed are laid and are connected, the insulating shell is in at least two parts split longitudinally and arranged to meet around the joint between the conductors. The invention is characterised in that a deformable electrically insulating plastics material is included in the bore of the tube of the shell and disposed in use to be adjacent the electrical conductor connector and arranged so that when the parts of the shell are closed around the conductor by the housing they form a unitary insulating barrier around the conductor within the shell and the deformable plastics material exudes to fill any gap between the parts of the insulating shell.

Preferably the insulating shell is formed in two parts with a central channel in each part in which the conductor is allowed to rest. The material of the insulating shell would preferably be polythene although any suitable mouldable or extrudable electrically insulating material may be used. The deformable plastics material is preferably laid in the said central channel.

A suitable deformable plastics material is a silicone-rubber based gel of a high viscosity. Insulating end caps may be provided at either end of the insulating parts to constrain the deformable plastics material and these end caps may be of a spongy deformable material. These end caps may be of a disc like nature and may fit within metallic end caps which are able to be slid over the ends of the cables before the connection is made and which can connect between a screening conductor on the cable and any screening of the joint arrangement itself. This screening may be provided either by the material of the housing which may be a aluminium or copper material or by applying an electrically conductive surface coating to the outside of the insulating shells.

The parts of the joint arrangement may be held together by suitable encircling clips or bands which are preferably releasable.

It will be appreciated that this joint provides the advantage of a tubular sleeve form of joint that is to say a lower level of necessary craft skills then taped, pitch or resin form of joint whilst avoiding the disadvantage of needing to prepare a long length of cable. It will be apparent to those skilled in the art that other advantages are provided. For example, fitting of the main split insulation tube is a very quick and simple operation requiring less skill and time than previous insulation methods. Similarly for this operation there is no need for any auxiliary tools and equipment such as heat.

Another advantage is that the insulating tube is not changed in shape during installation so that a test can be carried out on the tube after manufacture to verify its electrical integrity, with a high degree of assurance that the electrical integrity will not change during or as a result of installation.

Yet another advantage is that the annular space between the insulating tube and cable insulation can be large or small because it is filled with a flowable gel material. This means that a single joint size can accommodate a wide range of cable sizes.

In order that the invention may be fully understood, one construction of a joint arrangement in accordance with the invention and two modifications thereof will now be described, by way of example only, with reference to the four figures of the accompanying drawings. In the drawings Figure 1 is a longitudinal cross section through a joint showing it connecting two cable ends together, Figure 2 is an exploded view of the components of the joint, Figure 3 is a cross sectional view of the connector shown in Figure 1 along the lines 3-3, Figure 4 is a view of the assembled joint without the cables, Figure 5 shows a modified form of joint and Figure 6 a variation where a termination is used.

Referring now to the drawings and particularly to Figure 1 thereof, the connector is shown to connect the ends of two 36 Kv cables 1,2 which are dressed back to reveal the bare conductors 3, 4 respectively which are sealed into a connector 5 by a clamp screw (not shown). The cables 1 and 2 have an earthing screen of wire 6 which is trimmed back where the wire enters the joint. The wire is further trimmed to expose the insulation 7, and insulation shield 8. The joint itself comprises a housing 10 in which fits a split insulating tube 9 and the housing itself is split longitudinally to form two halves and the tube is of an outer configuration such that it also is in two halves, each of which fits snugly within the housing 10. Tube 9 is made of polythene and effectively comprises two shells which fit around the cables 1, 2. The inner surfaces of the shells do not actually make contact with the cables except at their ends but there is a space 11 forming a channel between the cables and the shells which is filled with a silica based gel material. The connector arrangement has end caps 12, 13 at either end which are constructed of a conductive metal, these end caps are a tubular nature and are stepped accordingly to the configuration shown so that the insulation 8 of the cable just passes through the bore of the most restrictive part of the end cap. The wider part of the end cap as shown houses a compressible insulating disc 14 of a plastics material. The end caps 12 and 13 are in a butting relationship with the housing 10 and make an electrical connection therewith. However the electrical connection is also made through an electro deposited screening 15 on the outside of the shells 9 and the electrical connection is continued to the screening wire 6 of the cables 1, 2 which are clamped by clips 16 to the cap 12, 13. The electrical screening is therefore continuous between the wires through the whole of the joint arrangement.

To assemble the joint the ends of the cables 1 and 2 are prepared to expose the insulation 7, and insulation shield 8 and are passed through the end caps 12, 13 which are fitted with the discs 14 prior to assembly. The two halves of the tube 9 are fitted into the two halves of the housing 10 and the channels in the shells are filled in space 11 with the silica based material being used. This material is highly viscous and adheres to the tube halves 9.

The electrical connection between the two ends of the cables 1, 2 are made with the connector 5 and the connector and any exposed ends 3, 4 of the conductor are covered with a semiconductive putty tape 17 up to the diameter of the insulation 7 of the cables 1, 2 and are then further covered by a semi-conductive self amalgamating tape 18 which extends over the insulation 7 as well as over the tape 17. A stress control tape 19 is then applied to the joint.

The two parts of the housing with the tube shells 9 are then placed around the joint and the shells are pressed together so that the gel exudes into the whole of the area 11 surrounding the joint. Not only does the gel exude into this area but it also is squeezed into the area between the two mating halves of the tube 9 at their junction 20 as shown in Figure 3. This then shares a continuity of insulation around the joint without there being any risk of air gaps between the mating halves of the two shells of the tube 9. Clips such as 21 are secured around the housing 10 and are tightened up to make sure that the two parts of the tube 9 are forced together against the compressive resistance of the gel. There are four clips shown in this example but more may be used if necessary. The purpose the of the discs 14 situated in the end caps 12 and 13 is to prevent the gel being squeezed longitudinally out of the connector housing, these end caps are moved in to position once the housing is placed around the connector. The wires 6 of the cables 1, 2 are then placed on to the restricted portions of the metal end caps 13 and the clips 16 are secured around them to make a good electric contact between the wires, end cap and the conductor by wrapping a semi-conductive tape 22 around the junction before the wire 6 is secured by the clip 16.

Figures 2 and 4 of the drawings show respectively in Figure 2 the various components of the connector in an exploded form and in the assembled form in Figure 4. It will be appreciated that the components fit together very readily around the cable and that the finished assembled connector is compact and is not too bulky on the profile of the cables.

The example given is for a single phase cable where only one core is to be joined.

It will be appreciated that if more than one phase is to be joined, for example in a three phase situation, then modifications to the configuration of the housing and particularly the internal profile of the tube 9 will be made. The shells of the tube 9 will most probably be formed in a number of parts and a central former may be necessary having recesses in which to lay the three parts of the connector. However, these are matters of design which would be readily able to be achieved by those skilled in the art.

Although semi conductive putty tape 17 and semi conductive self amalgamating tape 18 have been used in this example to cover the conductors and connectors, other known methods of providing a conducting connector shield may be used for example as in Figure 5 of the drawings. A moulded polymer conducting member-23 may be included in each half of the tube 9 so that on assembly this conducting member is brought into electrical contact with the conductors 3, 4 and the connector therebetween.

Similarly stress control tape 19 is used in the example but other known systems of providing stress control can equally be used. For example controlled impedance stress control system disclosed in United Kingdom patent application 2269712A can equally be used in this joint also.

Although a silica gel material has been used in the example, other forms of a plastics material having similar viscosity and electrically insulating properties can be used. Similarly the shells of the tube 9 do not necessarily have to be of polythene but any rigidly flexible insulating material could be adopted.

In the example the joint is used to connect two 36 Kv cables of substantially similar construction but it will be apparent that joints between different cable types can be made. For example a paper insulated cable can be joined to plastic polymer insulator cable using the invention provided known means are adopted to prevent deleterious effects of the paper cable impregnant on the polymer insulation.

It is sometimes necessary to operate an electric cable without drawing power from its end, for example when it is planned to carry out some future extension to a buried cable, it may be operated in a fore-shortened condition for a temporary period. Figure 6 shows how the invention can be used with an auxiliary component 24 in place of cable 3, 7, 8, 1 to provide such an end joint.

It is also commonly necessary to join more than two electric cables at one joint position for example when making a branch connection instead of a simple straight connection as used in the example. It will be apparent to those skilled in the art that the invention may readily be adapted to such joints by using a known form of branch conductor connector and modifying tube 9 and cap 13 and disc 14 so as to accommodate two cables on this side of the joint.

The invention enables a connection to be made between two cables in an effective and swift manner and which requires the minimum length of cable to be dressed and also requires no special tools. Furthermore, effective insulation of the joint is assured by the use of the gel material.

Claims (18)

1. An electrical joint arrangement comprising an outer housing having an insulating inner tubular shell, the shell having a central bore in which the conductors of two electrical cables to be longitudinally jointed are laid and are electrically connected, the insulating shell being in at least two parts split longitudinally and arranged to meet around the joint between the conductors characterised in that a deformable electrically insulating plastics material is included in the bore of the tube of the shell and disposed in use to be adjacent the electrical conductor connection and arranged so that when the parts of the shell are closed around the conductors by the housing they form a unitary insulating barrier around the conductor within the shell and the deformable plastics material exudes to fill any gap between the parts of the insulating shell.

2. An electrical joint arrangement as claimed in Claim 1 wherein the insulating shell is formed in two parts with a central channel in each part in which the electrical conductor connection is allowed to rest.

3. An arrangement as claimed in Claim 1 or Claim 2 in which the material of the insulating shell is of polythene.

4. An arrangement as claimed in any preceding claim wherein the deformable plastics material is preferably a silicon-rubber based gel of a high viscosity.

5. An arrangement as claimed in Claim 2 in which the deformable plastics material is preferably laid in the said central channel of the insulating shell.

6. An electrical joint arrangement as claimed in any preceding claim and including insulating end caps at either end of the arrangement to constrain the plastics deformable material in a longitudinal direction.

7. An arrangement as claimed in Claim 6 in which the end caps are of a spongy deformable material.

8. An arrangement as claimed in Claim 6 or Claim 7 in which the end caps are of a disclike nature.

9. An arrangement as claimed in any of Claims 6, 7 or 8 and including a metallic end caps connecting with the housing and including the insulating end caps at either end of the insulating parts.

10. An arrangement as claimed in Claim 8 in which the metallic end caps connect between a screening conductor on the cable and a screening of the connector arrangement itself.

11. An arrangement as claimed in Claim 10 in which the screening on the connector itself is provided by the material of the housing.

12. An arrangement as claimed in Claim 10 in which the screening is provided by an electrically conductive surface coating applied to the outside of the tubular shell.

13. An arrangement as claimed in any preceding claim in which the arrangement is held together by encircling clips or bands.

14. An arrangement as claimed in Claim 13 in which the bands are releasable.

15. An arrangement as claimed in any preceding claim and including insulating sealing means between the housing and the conductors being joined at their entry into the housing.

16. An arrangement as claimed in any preceding claim in which a moulded polymer conducting member is included and is brought in to contact with the conductors and the connector jointing them.

17. An arrangement as claimed in any preceding claim and modified by replacing one conductor with a terminating auxiliary component for the remaining conductor.

18. Electrical joint arrangements substantially as hereinbefore described and with reference to Figures 1, 2, 3 and 4, or 5 or as modified in Figure 6 of the accompanying drawings.