Abstract
We investigated the diagnosis of insulation performance in SF6 gas insulated apparatus like GIS. We performed time-resolved partial discharge (PD) measurements in SF6 gas using a matching circuit and a digital oscilloscope for a needle-plane electrode arrangement to investigate the frequency component of PD current pulse. We also measured phase-resolved frequency characteristics of PD pulse in SF6 gas using a spectrum analyzer. The experimental results revealed that PD pulse waveform differed depending on the voltage phase angle even when the magnitude of applied voltage and gas pressure were constant. This means that the frequency component of PD pulses differed depending on the polarity and the phase of applied ac voltage.
Consequently, we pointed out the necessity to select an appropriate frequency range for PD measurement depending on the frequency component of PD pulse.
