Adaptive differential protection of three-phase power transformers based on transient signal analysis

•We present a new formulation to differential protection of power transformer.•The method is based on transient signal analysis with discrete wavelet transforms.•The contribution of this work is the adaptability of the proposed methodology.•The protection method uses an adaptive threshold value for event discrimination.•The formulation is reliable, fast, accurate and easy for real-life construction.

This paper presents a three-phase power transformer percentage differential protection formulation based on transient signal analysis. The proposed formulation uses discrete wavelet transforms (DWT) to extract transitory features of non-stationary signals with fast transition, mapping the signal in time–frequency representation. The proposed formulation was implemented on MATLAB® environment and evaluated through a case study using BPA’S ATP/EMTP software. Comparative test results are presented showing that the proposed formulation is highly reliable, fast, accurate and easy for real-life construction.