Improvising Differential Protection Scheme to Differentiate Between Internal and External Fault in Presence of Charging Current

The paper presents a methodology on how to discriminate: internal and external faults; for a transmission line protected by differential protection scheme, during the presence of charging current. Transmission line with high voltage levels (400-765kV) peculiarly has this disadvantage. Various plots for a Distributed Transmission line Model with Source at both the ends” with internal and external faults were plotted and analyzed. Through the comparison of current samples at zero crossings for remote end and local end buses, after that implementation of proposed DSA (Difference Squared and Averaged) theory, were able to distinguish whether the fault is internal or external. The techniques better compared to conventional techniques since threshold taken under consideration; obtained through experimentation on various system models for varying degree of parameters via certified thresholding method. And the uniqueness lies with the fact that it provides a provision to distinguish transient disturbances from internal fault.