Feasibility study to use the current transformers as inductive partial discharge sensors

Partial discharge (PD) is the most important factor in gradual insulation deterioration of high-voltage (HV) power equipment, and then PD trend monitoring is a great issue for their condition assessment. Impulsive high-frequency PD current/voltage signals can be detected by using electrical sensors, e.g. inductive/capacitive sensors. A comprehensive feasibility study is carried out to use the power frequency current transformers (CTs) that are already installed in medium voltage and HV electrical power systems instead of high-frequency CTs. To achieve this aim, frequency response of a sample protection CT is extracted experimentally and it is fitted to appropriate transfer functions to access the related frequency characteristics. Regarding improper CT frequency response and its extreme variations in different frequencies, reversed transfer function is obtained to apply to CT secondary signals for reconstructing CT input PD pulses. Two types of artificial PD pulses are examined to validate the proposed method and the experimental results show that power frequency CTs can be used for PD detection and measurement in some frequency bands.