Research and Identification of DC Magnetic Bias of Transformer Based on Discrete Wavelet Transform

Abstract

In recent years, with the continuous development of the DC transmission system, the DC bias of the transformer in the AC power grid has occurred from time to time, DC bias is an abnormal working state of the transformer. Therefore, research and identification of DC bias of transformer is of great significance. This paper is based on PSCAD software to research DC bias of single-phase three-winding transformer. The excitation current, the changes of each harmonic and total harmonic distortion rate during DC biasing are given. Then based on the Discrete Wavelet Transform (DWT) to identify the low-frequency components in the excitation current, according to the characteristic of low frequency component, which can be used as an effective judgment for the DC bias fault of the transformer.