A Novel Histogram for Partial Discharge Signals in HV Insulating Systems

A technique for relating measurable electrical quantities with energies dissipated inside a void in highly electrically stressed insulation is presented. It is based on measuring, for each apparent discharge level qe, the algebraic sum of the external energy pulses of all discharges having a value qe and occurring over some cycles of test voltage. Theoretical investigations show that the results of such external energy summations are equal to the energies dissipated in the void. A novel histogram is also suggested which relates the apparent discharge amplitudes with their respective energies in the void. Experimental tests were carried out under controlled conditions with samples of thermoplastic and thermosetting dielectric materials. By means of a digital computer-driven instrument, built in our laboratory, good agreement between theoretical and experimental investigations has been found. Work is in progress to extend the application area of the above measurements to complex insulating components.