Transient Analysis Considering CT Saturation of Three Phase Three Winding Transformer System

In this paper, in order to improve the reliability of IED operation by relay signals due to the saturation of CT magnetic material, a transient analysis considering nonlinear CT saturation of the three phase three winding transformer system is performed. First, the Jiles-Atherton model equation for nonlinear CT magnets is formalized. After selecting a domestic actual three phase three winding transformer system, the related system parameters are collected. We model a CT based three winding transformer system using PSCAD, an EMT tool, and verify its validity in steady state. Finally, the hysteresis curves and transient currents of the magnetizing inrush and fault state are analyzed and evaluated by performing simulations under various conditions.