Ensuring reliable partial discharge (PD) calibrator measurements: service for traceable charge calibration

This work presents our approach to calibrating partial discharge (PD) calibrators, key devices used to simulate a known apparent charge for high-voltage testing, through international NMI comparisons. Partial discharges, which signal insulation degradation in equipment such as cables, transformers, and electrified propulsion systems, are measured in picocoulombs per IEC 60270. Our service employs two complementary calibration methods: the active integration method, optimized for low-charge measurements (0.1–20 pC), and the numerical integration method, best suited for higher charges (20 pC to 10 nC). By comparing the nominal calibrator settings with our measured averages and evaluating the expanded uncertainties, we demonstrate that our results are both accurate and traceable. Participation in NMI comparisons further validates our calibration methods, ensuring international consistency and reliability. This new calibration service, while still under development, represents a significant step toward improved high-voltage PD testing.