Surface discharge current pattern properties of porcelain insulator specimen on various pressures

Abstract

This manuscript presents the patterns of surface discharge currents due to pressure influence on the porcelain insulator specimen. It was subjected by the high voltages in a hermetically sealed chamber, where the pressure could be adjusted and measured simultaneously. The applied voltage and discharge current waveforms were recorded by a storage digital oscilloscope, transferred and saved to a computer. The discharge current waveforms were analyzed by using FFT, correlation coefficient and principal component analyses. The yielded discharge currents were in intermittent conditions. After the fundamental, the second highest harmonics was third. The discharge current amplitude increased significantly as the pressure reduced. The characteristics between discharge current and applied voltage magnitudes were more extremely non-linear as the pressures reduced, especially they were lower than the atmospheric pressure. The discharge breakdown voltage increased as the air pressure rose. It required a voltage magnitude threshold to be discharge. Almost harmonics had the negative correlation coefficients on the pressure, except the THD which had 0.45. The increasing THD was more dominantly caused by the increasing first harmonics which was slighter than the increasing remaining harmonics.