Identifying magnetizing inrush in power transformers based on symmetry of current waveforms

Abstract

This letter proposes a novel method for the discrimination between magnetizing inrush and internal fault in power transformers based on the similarity of the current waveforms. The proposed method first normalizes and sorts the sample points of the differential current in a full fundamental frequency cycle to obtain a new sequence which is independent of the magnitude and initial phase angle of the original signal. Afterward, three indices are introduced to measure the similarity between the new sequence and a template, which are used to discriminate the inrush from an internal fault. Simulation studies demonstrate the effectiveness of the proposed method and its advantages over the conventional second harmonic restraint method. © 2017 Institute of Electrical Engineers of Japan. Published by John Wiley & Sons, Inc.

Identification Methods for Transformer Turn-to-Turn Faults and Inrush Current Based on Electrical Information

“…The principle of waveform symmetry is to use the front/post half-wave symmetry comparison of the derivative of the difference current (to reduce the influence of aperiodic components), and to identify the inrush current based on the comparison result. The principle of waveform symmetrical inrush current recognition is not affected by the offset of the DC component, and is an extension of the discontinuous angle inrush current criterion, and is easier to implement than the discontinuous angle inrush current criterion [40,41].…”