A new algorithm for avoiding maloperation of transformer differential protection

摘要

A new algorithm for avoiding maloperation of transformer differential protection during external faults caused by current transformer (CT) saturation is presented. The algorithm is based on the time-domain phase comparison of the primary and secondary currents of power transformer (PT). The algorithm serves for identification of faults which occurred outside the protected zone. The presented algorithm could be used as an additional criterion for operation of transformer differential protection. Its application would greatly improve the correct operation of differential protection and so increase its security. The required input signals for testing the algorithm have been generated by computer simulations. The paper presents the algorithm and results of the performed tests.