Modelling & simulation of transformer biased differential protection scheme in laboratory environment

The transformer is vital components in power system network. Because of its simple construction, it is a more reliable equipment. To simulate the model of differential relay many problems, such as Tap changing, inherent phase-shift of currents in transformer, CT ratio, Non identical CT. According to the traditional protection the power transformer is balanced by interposing the CTs on star side, the Simulink model has been simulated in MATLAB. Keeping design principle in mind the parameter of transformers was obtained by Open circuit and Short Circuit test in the laboratory environment. Differential relay was modeled using Simulink. The calculated parameter were than simulated in MATLAB/Simulink the differential relay is simulated as per the panel available in laboratory.

I. Introduction

Transformers is one of the vital components of power system. They are more expensive in the distribution or transmission substation, whenever it undergo for service due to breakdown. So, their protection is needed. The most important protection for transformer is differential protection [1] [10]. In recent 10 years the mal operation of transformer is 30 percentage. The reason behind this is the hardware implementation, protection scheme are not perfect [6]. Any transformer protection should operate correctly under the internal fault and external fault. With the traditional protection the vector group transformer, to regulate the unequal transformer ratio, CTs matching is done by interposing CT [1] [2].