Transformer Protection Based on Fault Transient Detection

This paper presents a new relaying scheme based on the polarity comparison for power transformer protection. Wavelet transform presented in the paper is sued for extracting the transient signal feature of the internal and external fault current waveform, the paper then presents a criterion, which can reliably distinguish between internal faults and inrush currents. All the conclusions are verified by simulation using the EMTDC, the experimental results indicate that this technique is effective under various fault conditions.