MEASUREMENT SCHEME FOR SIGNALS ON CORE EARTH CONDUCTOR OF POWER TRANSFORMERS

Xuezhi Ke, Zhaohui Li, and Hong Wang

Keywords

Power transformer, core earth signals (CES), wide-band sensing,uninterrupted acquisition, real-time feature extraction

Abstract

Multiple signals can couple to a core earth conductor of a power transformer and constitute core earth signals (CES). The existing CES measurement approaches ignore most of its signals. In this study, we develop a novel measurement scheme for CES. First, we use a wide-band CT clamped on the core earth conductor to capture all kinds of signals. Secondly, we design a signal conditioning adapter to amplify and condition the output signals of the CT. Thirdly, we apply a high-rate sampling card to acquire the conditioned signals uninterruptedly. Lastly, we develop a signal processing procedure to extract and correct all the signal features from the sampling data in real time. This new scheme has been verified in a lab and applied to the field. The advantages of this new measurement scheme are as follows. (1) Wide sensing band can couple both power frequency signals and higher frequency pulses. (2) Uninterrupted acquisition mode ensures to acquire both steady signals and transient signals. (3) Special data processing procedures make it can extract all the signal features accurately in real time. (4) Innovative RMS correction function contributes to the low relative error (<3%).

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