Analysis of shunt reactor energization at EHV substation and its effects on CT: A case study

This paper presents an overview of transient phenomena occurring during energization of shunt reactor at EHV substation. Unsymmetrical phase currents during shunt reactor energization are analyzed and its effects on protective devices are discussed. High DC offset inrush currents with very high time constant during energization of reactor can cause mal-operation of zero sequence ground relays. High value of DC offset in the current might lead to current transformer saturation. Error in phase difference of the currents of saturated CTs at HV and LV side of shunt reactor leads to spurious trip of differential protection relay. This case study is done for 1200/765/400/200 kV Wardha substation of Power Grid Corporation of India Ltd, Western region, 1, India. Simulations are carried out using Alternate Transient Program/Electromagnetic Transient Program (ATP/EMTP) software.