Partial discharge measurements: possibilities and limitations

Several aspects of partial discharge (PD) measurement and processing of PD data are discussed. It is pointed out that the ABC equivalent is not a fully valid equivalent of a void in the insulation and should be used with some care. The use of broadband measuring systems gives a gain in sensitivity, but calibration can be a problem when they are used on equipment with large geometrical dimensions. Recording the energy pulses following a PD has a physical significance only if there is only one PD per half-cycle per void. Sensitivity is dependent on the position of a void and the nominal voltage of the equipment tested. The inception of PD in small voids is found to be subject to considerable statistical time lag in the absence of artificial radiation