The effectiveness assessment of calibration and measurement of PD apparent charge quantity

In the Partial Discharge (PD) measurement on transformer, the discharge quantity is calculated from the offline calibration. The calibrating waveform is standardized by IEC 60270:2000 with a rise time < 60 ns, or an equivalent up-band frequency > 6MHz. But the PD measuring instruments in use are standardized by the same document with an up-band frequency less than 500 kHz. Most of the energy is lost. A new measuring method with a bandwidth of 30 MHz is proposed in this article. At such high frequency, the influence of bare conductor inductance is not negligible. Such influence is lab measured and theoretically calculated. A new co-axle calibration sensor is demonstrated. The measurement results show good frequency response and sensitivity.