A novel technique for differential protection of power transformers

This paper presents a successful implementation of d-q axis and wavelet packet transform based hybrid technique for protection of power transformers. This characterization helps to develop an improved differential relay to detect and discriminate internal faults from inrush currents in power transformers. This hybrid method provides accurate information with only one level of the wavelet packet transform (WPT) of the d-q components of the differential current for power transformer protection. A real-time experiment has been carried out for different normal and abnormal operating conditions such as magnetizing inrush and internal incipient faults for different cases of loading to test the efficacy of the proposed algorithm. The experimental results show the efficiency and reliability of the proposed technique.