Selection of p.v.c.-insulated cables for 415 V motors in CEGB power stations

The choice of size of power cables for connections between power-station auxiliary motors and associated starters invariably has to be made before precise information on the cable environment and type of drive is available. The paper analyses the various factors that govern the selection of these cables, and offers a synthetic solution to the problem for all conditions normally encountered, so that for a given duty and route length the necessary cables may be scheduled in advance of the final operating data. Each rating of squirrel-cage motor with direct-to-line starting is considered in conjunction with cable characteristics, circuit parameters, switchgear, protection, earthing, environment and economics. The paper concludes with a recommended range of p.v.c.-insulated cable sizes for each motor rating to meet normal conditions.