Partial Discharge Measurement of GIS With Damped AC (DAC) Voltage: Case Study for the Particle on Insulator

Off-line PD measurement is important for GIS. Interference signal generated by frequency-tuned resonant test set has a huge impact on PD measurement. Damped alternating current (DAC) voltage has been widely used in field testing of power cable and has no power interference. Whether the DAC can be used for PD testing of GIS still needs to be studied. The particle on insulator can greatly reduce the dielectric strength compared to clean condition, which is a very destructive defect. In this paper, the PDIV of AC and DAC were measured, the number of discharges per cycle was counted, and the PRPD pattern was obtained. For the defect model we set up, test results show that PDIV is independent of waveform and frequency; PD distribution area and the number of PDs per cycle increase with frequency. This is because SF
₆
gap needs to recover its dielectric strength after discharge. When the recovery time and discharge interval are on the same order, it's possible to excite PD at a lower voltage, thereby increasing the number of PDs in each cycle. DAC is effective for detecting the defect of particle on insulator in GIS, and the PD activity of DAC is more obvious.