Online and Offline Partial Discharge Measurement in Rotating Machines using Transient Earth Voltage Sensors

Abstract

The purpose of this study is to establish an online partial discharge (PD) diagnosis method in rotating machines using transient earth voltage (TEV) sensor and high frequency CT sensor which are relatively inexpensive and easy to install, as compared to aging state diagnosis by the conventional offline diagnosis. In this paper, on-line partial discharge measurements using several TEV sensors were performed and compared with signals detected by patch antenna and high-frequency current (CT) sensors, which are commonly used sensors. The results show that TEV sensor is relatively simple and useful for the online PD monitoring. An attempt is also made to provide a new index for the online measurement instead of the maximum discharge charge amount <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q_{\max}$</tex> , which is a widely recognized evaluation index in the conventional offline test. In order to clarify the relationship with the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$Q_{\max}$</tex> result of the offline test, online PD measurement is performed using TEV sensor and CT sensor. The relationship between the offline and online PD measurement is investigated.