Abstract

Power transformers are vital and expensive components of electric power systems and it is necessary to protect them from internal faults. Differential protection is based on differential current. Occurrence of some phenomena such as inrush current, over excitation, saturation of current transformers and mismatch of current transformers cause the differential relay to operate incorrectly. In this paper, fuzzy logic is used as a powerful mathematic tool. In this method of protection, algorithm is based on ruled out non-internal fault phenomena. The results of simulations show that fuzzy protection system is able to detect occurrence of fault in less than half a cycle and this method improves protection system, satisfactorily.       

Key words: Differential protection, power transformer, fuzzy logic.