ABSTRACT
The rating, or voltage class, of a cable is based on the phase-to-phase voltage of the system even though it is in a single or three phase circuit. For example, a 15 kV rated cable (or a higher value) must be specified on a system that operates at 7,200 or 7,620 volts to ground on a grounded wye 12,500 or 13,200 volt system. This is based on the fact that the phase-to-phase voltage on a wye system is 1.732 (the square root of 3) times the phase-to-ground voltage. Another example is that a cable for operation at 14.4 kV to ground must be rated at 25 kV or higher since 14.4 times 1.732 is 24.94 kV
Figure 4-1 Voltage rating.
