Handbook of Electrical Installation Practice - BeKnowledge

Switchgear 381
Fig. 14.8 Typical UK switchgear unit with vertically isolated withdrawable bulk oil
circuit-breaker.
The cable compartment was traditionally designed for the termination of paper
insulated cables, and made provision for filling with bitumastic compound as insulant
for the completed termination. Nowadays there is increasing use of elastomeric
cables terminated in air-filled cable compartments, or sometimes even paper insulated
cables are terminated in this way. The introduction of heat shrinkable plastics,
or elastic ‘cold-shrink’ sleevings, has facilitated the adoption of this technique.
Some of these sleeves can be made semiconducting, which facilitates the grading of
the electrical stress along insulation between the cable core and the sheath at the
termination.
Another technique for the termination in air of polymeric cables involves the use
of proprietary cable connectors. These have two forms. One has an inner and outer
semiconducting sheath which allows for the earthing of the outer coating, and which
uses termination components that also deal with the problem of stress grading of
the exposed cable insulation. The other type is unscreened and just takes care of