Zaštita tronamotajnog energetskog transformatora zasnovana na faznoj komparaciji struja

Abstract

This paper presents a new algorithm for three-winding transformer protection against internal short circuits. The algorithm is based on the application of the digital phase comparison of currents measured at the primary, secondary and tertiary terminals of the power transformer. The applied digital phase comparison does not calculate the angle between the two currents compared in phase, but uses the method of integration of the product of two signals within one basic semi-period of the signals. In order to provide selective protection in the case where the power transformer has only one of its three windings connected to the active network and the other two windings feeding passive networks, an overcurrent function has been added to the digital phase comparator. The paper shows that the application of the new algorithm can successfully detect the internal faults of the three-winding transformer and ensure timely tripping of protection. The signals obtained by computer simulations were used to verify the operation of the proposed algorithm. The algorithm and test results are given in the paper. Index Terms- power system protection, power transformer, digital phase comparison, fault discrimination.