Challenges in Calibrating an Unconventional Partial Discharge Measurement System for Pulsed Voltages

In this paper, the signal of an unconventional partial discharge (PD) sensor is analysed on characteristic parameters both in time domain and frequency domain. This is done to find correlations to the standardised apparent charge qa according to IEC 60270 and therefore make the used unconventional PD measurement system comparable to the conventional system. The benefit of the unconventional PD sensor is that it can be used even with pulsed voltage waveforms containing high switching noise due to high dV/dt. Therefore, a calibration of this system would enable a fair comparison to conventional sine wave test stands. The measurements for this investigation are mainly performed in a conventional sine wave test stand, where both PD measurement systems are mounted to compare their signals. As unconventional PD sensor a self-built PD Rogowski sensor with a high bandwidth is used. The characteristic parameters considered and analysed in the time domain are mainly the PD waveform, its time integral, the maximum and average peak amplitude of single PD events, the here introduced “average PD event” as well as the absolute PD quantity. In the frequency domain it is analysed if there are characteristic frequency bands, where the signal intensity correlates with the apparent charge. The derived findings are then examined further using only the unconventional sensor in a test stand for pulsed voltage waveforms.