Application of TEV Sensors to PD Measurement for Capacitor Voltage Transformers

Abstract

This study aims to establish an insulation diagnosis method based on partial discharge (PD) measurement for capacitor voltage transformers (CVTs). Since aged CVTs over 50 years have been used in substations, an insulation diagnosis technique for CVTs is urgently required. Recently, transient earth voltage (TEV) sensors are used as PD detection sensors in transformers. Since the TEV sensors detect leakage electromagnetic waves and ground line currents, the PD signals in CVTs can also be detected by TEV sensors. However, the applicability of a TEV sensor to PD measurement in CVTs has not been verified. In this paper, the applicability of a TEV sensor for PD detection in the actual CVT (24-year-old) is discussed. As the experimental results, it was found that the TEV output has a good correlation with the PD charge over a wide range from 60 pC to 60,000 pC with the correlation coefficient as high as 0.99. Therefore, the TEV sensor is effective as a PD sensor for CVTs.