Cable terminations and live conductors within air-insulated enclosures (insulation co-ordination) for rated a.c. voltages of 7,2 kV and up to and including 36 kV
This specification covers the requirements for enclosures for the termination of cables and housing of live conductors in air, for use indoors or outdoors, at rated a.c. voltages of 7,2 kV and up to and including 36 kV.
2 Detailed requirements for the design and construction of the enclosures are in general not specified. It is expected that these will be covered by the requirements specified for the equipment (e.g. the switchgear or transformer to which the enclosure is connected or of which the enclosure will form part, where appropriate), or, alternatively, they will be left to the manufacturer. The parameters and leading dimensions to be considered are, however, specified and may be applied to enclosures which either form an integral part of major equipment or are similar to cable boxes as specified in BS 2562.
3 In the case of cable termination enclosures associated with transformers, bushings constitute the terminal fixing point for the cable. Where cables are terminated within switchgear enclosures, the fixing point can be bushings, post insulators or connections to current transformers. In the case of cable junction boxes, post insulators constitute the terminal fixing point for the cable.
4 The method of cable termination and terminal fixing cannot be ignored when determining the requirements for cable termination enclosures. This specification deals with the requirements for the following types of termination within enclosures:
a) Type 1 termination: air insulated (see 3.2.7);
b) Type 2 termination: shrouded (see 3.2.8);
c) Type 3 termination: unscreened separable connectors (see 3.2.9); and
d) Type 4 termination: dead break screened separable connectors (see 3.2.10).
5 Since the insulation co-ordination requirements for bare or insulated live conductors supported by post insulators or other insulating materials within an enclosure are considered to be the same as those for type 1 and type 2 terminations, this specification serves as a general design guide for air-insulated enclosures.
6 The enclosures covered in this specification are not intended for use in hazardous atmospheres.