Adaptable Differential Relay using Fuzzy Logic Code in Digital Signal Controller for Transformer Protection

Power Transformer is one of the critical and vital links to maintain uninterrupted power supply in the power systems. With growing demands in power system it is necessary to have a speedy and reliable protection module which should quickly initiate the tripping during internal faults and should be stable to avoid tripping during inrush, over excitation and external faults. The work reported in this paper demonstrates the use of Fuzzy Logic code written in 16-bit Digital Signal controller (dsPIC DSC) for implementation of percentage differential Relay with inrush detector as a part of Power Transformer protection. There is flexibility to generate various percentage bias characteristics having varying slope and capability to discriminate Inrush and fault Currents to avoid false tripping. The laboratory model is developed to test Differential relay with real time signals replacing CTs' by Current Transducers LEM-HXS in primary and secondary of three phase transformer interfaced with Digital signal controller which acts as a Differential relay controlled by Fuzzy Logic Code in C. The performance of this Adaptable Differential relay with stand alone model is having capacity to generate fast tripping signal with good accuracy.