Validation of partial discharge calibrators for small charge rates

Partial discharge measurement is one of the standard tools for diagnosing the state of high-voltage insulation systems. Before the measurement, it is necessary to calibrate the entire circuit using a calibrator that generates an accurate charge value. There are now emerging requirements to increase the verification accuracy of these calibrators for charge values less than a few pC. In this paper, a comparison is made between two possible calibration procedures, namely the numerical integration method and the procedure using special charge-sensitive amplifiers. The comparison is made based on uncertainty analysis and practical laboratory measurements. The results show that the use of charge-sensitive amplifiers brings a significant reduction of the calibration uncertainty in the small charge region.