Partial discharge measurements-frequency related considerations

Partial discharge (PD) test circuits have been developed for various test series in different gases in the 13.3 Pa to 101.3 kPa pressure range with a needle-plane electrode arrangement. (The purpose of the test series is to establish results in terms of PD inception voltage, waveforms and rise times.) The paper describes features of the initial and improved test circuits, in terms of components, circuit layout, grounding and safety aspects. Impedance vs. frequency measurements performed in the 1 kHz-200 MHz frequency range are reviewed and discussed. PD current waveform measurement procedures are also reviewed. Waveform measurements are analyzed in terms of the initial rise time and the discharge rate of the coupling capacitor.