The use of TEV sensors for online PD detection in oil-filled transformers

This publication presents the results of measurements performed to verify if the use of transient-earth voltage sensors can be successfully applied to detect partial discharges on in-service oil-filled power transformers. Those investigations were performed both in the laboratory and in the field. For the investigations performed in laboratory and offline in the field, partial discharge measurements were performed synchronously using transient-earth voltage sensors and sensors installed at the bushing tap, to obtain a comparison which is compliant and calibrated according to IEC 60270. For the measurements done online, synchronous PD measurements were performed using transient-earth voltage sensors and other non-conventional sensors such as high-frequency current transformers and ultra-high frequency antennas for comparison. In addition, the signals obtained from the transient-earth voltage sensors were also successfully used to trigger an acoustic partial discharge localization instrument. It was found that TEV sensors can be used to perform completely non-intrusive PD detection on oil-filled transformers, without the need of an outage or pre-installed sensors.