On the Use of High-inductive Sensors for Partial Discharge Signals Measurement by the Electrical Method in the Factory Test Environment

Abstract

The article discusses theoretical and methodological aspects of implementing a test setup for partial discharge (PD) measurements in a factory test environment with application of high-inductive sensors based on the voltage transformer principle. The main advantages of this approach are the ability to detune the PD sensor signal from high-frequency noise and the relatively low frequency of the sensor oscillatory response, which simplifies the requirements for the analog-to-digital converter (ADC) and provides error-free calibration. Factors affecting the test setup sensitivity are analyzed considering stray capacitances of the high-voltage circuit and the measuring circuit with respect to the sensor secondary winding. It is shown that the sensor magnetization and leakage inductances do not affect the test setup sensitivity, due to which they can be used to obtain the desired sensor oscillatory response frequency by varying the ferrite core dimensions and turn numbers of the primary and secondary windings. The optimal design parameters of the sensors in the cases of using the ADC low- and high-impedance inputs are studied. The origin of the sensor’s double-frequency response both during calibration and PD measurements is explained. Signal filtering methods are proposed, which, together with using high-inductive sensors, provide the ability to measure PD with an apparent charge of 1 pC in factory test environment.