Discharge Characteristics for Surface Discharges at Variable Atmospheric Pressure

The results of partial discharge (PD) measurements performed by an electrode arrangement able to generate surface discharges on flat insulation specimens are presented and discussed in this paper. Focus is on the PD characteristic behavior, including pattern and PD pulses, under AC 60 Hz, as a function of atmospheric pressure, from standard atmospheric pressure (SAP) to 0.2 bar, which are typical pressure levels for commercial aircraft cruise altitude. It is shown that partial discharge pulse shape does not change the frequency content significantly in the test pressure range, that the partial discharge inception voltage decreases noticeably with pressure and the phase resolved PD pattern has some changes in terms of shift from the zero voltage which might affect identification robustness. Overall, partial discharges can be detected effectively using the same software, sensors, and analytics as at SAP, but further investigation is required to understand the pattern shift.