Bigharaz - Applied Electromagnetic Research Excellence Center Department of Electrical and Computer Engineering University of Tehran Tehran, Iran
Sanaye-Pasand - Applied Electromagnetic Research Excellence Center Department of Electrical and Computer Engineering University of Tehran Tehran, Iran
Zangiabadi - Applied Electromagnetic Research Excellence Center Department of Electrical and Computer Engineering University of Tehran Tehran, Iran

In this paper design, computational aspects and experimental results of a microprocessor based digital transformer differential relay is described. Half cycle Fourier algorithm is used to estimate current phasors. Performance of the proposed relay is tested for different faults including internal and external faults. The ability of the relay to restraint for inrush current is discussed and demonstrated. Test results of the proposed algorithm highlight the abilities of the algorithm. Test results for external fault, internal fault and inrush current are presented in the paper.

Digital Protection, Transformer Differential Relay, Half Cycle Fourier Transform