Evaluation of a calibration technique in measuring partial discharges inside mineral oils with a high‐frequency current transformer (HFCT) sensor: A case study

Abstract Partial discharge is one of the main reasons for insulation degradation in high‐voltage apparatuses. Partial discharge is an ineluctable phenomenon that happens when a high electrical field is adjacent to an insulator. High‐frequency current transformers are widely used for detecting partial discharge current in high‐voltage equipment. Determination of the apparent charge in pico coulombs is essential for having a common understanding of results and verifying that the measuring system can obtain specified partial discharge magnitude correctly. To this end, a high‐frequency current transformer sensor and a partial discharge calibrator have been prepared to measure the current of the partial discharge (PD) pulses inside mineral oil. The constructed PD calibrator has been evaluated. The high‐frequency current transformer (HFCT) sensor has been simulated using a mathematical model‐based AC analysis and has been characterized and then calibrated using a calibration technique to measure the apparent charge of the PD pulses. Experimental results show the effectiveness of the HFCT sensor and the proposed calibration method.