Electricity: conductors and insulators – With fluids or vacuum – Conduit or cable end structure
Patent
1985-05-14
1986-08-19
Askin, Laramie E.
Electricity: conductors and insulators
With fluids or vacuum
Conduit or cable end structure
174 73R, 174 80, H02G 1502
Patent
active
046071342
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a termination of a cable for high-tension alternating current and insulated with a solid polymer material. The termination is primarily intended for a cable with an operating voltage of 12 kV or 24 kV.
BACKGROUND
Cable terminations with termination details of synthetic rubber of the ethenepropene-diene rubber (EPDM) type are known, and an example of one is described in the Swedish examined application published Jan. 8, 1979 under the number 405,904.
SUMMARY OF THE INVENTION
In the termination of the invention there are included at least two beaker-shaped caps of surface-leakage-resistant insulation material, which are pushed over the end of the cable divested of exterior insulation, with the cable passing through the bottom of the cap, with the bottom part of the cap first put in place surrounded by the opening of the second cap and so on, each cap enclosing a separate, gas-filled space. The opening of the cap fitted first is closed by a disc insulatingly surrounding the cable.
The separate gas-filled space in each cap is filled with an insulating gas, which may be sulphur hexafluoride.
The arrangement of gas-filled spaces in the cable termination affords the advantage over previously known cable terminations that the weight of the termination is reduced, since a previously used solid insulation material has been replaced by a gaseous insulation. Furthermore, the termination with retained low weight has an outside diameter so large that the electrical field strength in all the incorporated parts is low and the risk of surface leakage current is small.
When the cable termination is to be installed outdoors, caps are used which are formed about their openings with a collar increasing surface creeping distance.
Where the cable outer sheath has its boundary, the cable is surrounded by a field control device, known per se, and this is surrounded by one of the caps, preferably the one pushed on first.
BRIEF DESCRIPTION OF DRAWINGS
An embodiment of a cable termination in accordance with the invention will now be described, with reference to the sole FIGURE of the accompanying drawing, which illustrates a longitudinal section through the termination, its caps and their collars for increasing the surface-leakage path.
DETAILED DESCRIPTION OF A BEST MODE FOR CARRYING OUT THE INVENTION
As will be seen from the drawing, in the embodiment of a cable termination in accordance with the invention a cable 1 for high-tension AC and insulated with solid polymer material is stripped at its end and provided with a cable lug 2. For a distance 3 nearest the lug, the cable is divested of its outer sheath and its conductive screening layer so that only the solid polymer material insulation remains. The boundary for the exterior insulation of the cable is surrounded by a field control device 4, known per se, for smoothing electrical field strength acting on the insulation in the longitudinal direction of the cable.
The end of the cable is surrounded by a plurality of tubular or beaker-shaped caps 5A, 5B of surface-leakage resistant insulation material, which in this case is EPDM rubber. The caps 5A and 5B are mounted on the cable with their closed bottoms facing towards the end of the cable, holes in the bottoms of the caps surrounding the cable with a tight fit. The bottom part of the cap 5A fitted first is surrounded by the opening of the second cap 5B; the second cap being fitted over the first one to about a third of its length. The first-fitted cap 5A surrounds the field control device 4.
The first-fitted cap 5A has its open end closed by an insulating disc 6, which is placed on the cable beforehand.
Gas-tight 7A, 7B are arranged in each of the caps 5A, 5B, by placing the caps inside each other and closing the cap 5A with the disc 6. The closed spaces are filled with insulating gas, sulphur hexafluoride in this case, by installing the caps on the cable in an atmosphere of SF.sub.6.
To advantage, when the termination is to be installed outdoors, caps are used which ar
Askin Laramie E.
Kabeldon Aktiebolag
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