Selection of Cable Insulation Levels

In most present cable specifications, the selection of the proper insulation level to be used is based on whether or not the system is grounded. Since the detrimental effects to which the cable insulation is subject during ground faults depend upon both the maximum voltage impressed on the insulation and on the duration of the fault, it is felt that both factors should be considered in selecting the insulation level. With this in view, three basic insulation levels are proposed.