An Experimental Implementation of the $dq$-Axis Wavelet Packet Transform Hybrid Technique for Three-Phase Power Transformer Protection

A successful development and implementation of the dq-axis components and the wavelet packet transform (WPT)-based hybrid technique for power transformer protection is introduced in this paper. In this approach, the high-frequency subband contents of the dq-axis components of the differential current is extracted using the WPT. This characterization helps to provide enough information to efficiently detect and discriminate internal faults from inrush currents in power transformers. This hybrid method provides accurate information with only one level of the WPT of the dq-axis components of the differential current for power transformer protection. A real-time experiment is carried out for different normal and abnormal operating conditions, such as inrush and internal faults for different cases of loading, to test the efficacy of the proposed algorithm. The experimental results show fast, accurate, and reliable responses to all different types of disturbances that may occur in power transformers.