Comparison and Analysis of PD Measurements under DC Voltage in Different HV Laboratories

Partial discharge measurement is an important diagnostic tool for evaluating isolation systems. Under AC voltage, this method is well defined by IEC 60270 and accepted worldwide for industrial testing by manufacturers and operators. This standard also suggests how to measure under DC voltage. Investigations of different insulation arrangements under DC voltage have already been presented in earlier contributions in the past. When measuring the same specimens under the same conditions for AC voltage, the partial discharge measurement results showed great agreement with small deviations. However, there were large differences in the partial discharge results under DC voltage for the same insulation arrangements. A round robin test of three HV laboratories of the participating universities therefore defined a measurement program, which was applied in two round robin tests with typical defects (void in epoxy-resin, needle-plate in air) of the same test specimens. The results were already previously published at the conferences ISH 2017 in Buenos Aires and VDE Hochspannungstechnik 2018 in Berlin.