Influence of System Parameters on Current Transformer Saturation in Power System

Current Transformer (CT) is the prime sensing device in power system for protection applications. Certain parameters of external circuit and CT itself may influence the operation of a protective schemes. During high fault current, its operating characteristic may disrupt and it creates nuisance operation of protective devices. Execution of CT in power system may affected by mismatch in CT ratio, CT saturation, error in measurement, fault inception angle (FIA), greater relay burden, remnant flux and several adverse effects in power system. Thus, it is a necessity to evaluate the performance of CT during such anomalous operating situations and its impact on the relaying schemes. Some special effects on current signals are generated using PSCAD software under different CT saturation conditions and system parameter variations. Time to enter the nonlinear region of operational protective CTs is additionally important and its refinements are also a major issue. This article covers the impact of variation in internal and external constraints of a system on saturation of CT during protection of the power system network. It has been observed that the behavior of CT changes from case to case due to linear and nonlinear operation during the different fault and fault inception angle.