Simulation and Analysis of Transformer Inrush Current and its Impact on Current Differential Protection

A transformer model was built using PSCAD. The generation mechanism, waveform characteristics and influence factors of inrush current were simulated and analyzed. Combined with transformer differential protection, this paper discussed the conventional methods to identify inrush current and the operation logic to prevent mal-operation caused by inrush current. The typical transformer differential protection operating criteria were also simulated under different fault conditions. The results show that digital simulation can properly present inrush current waveform characteristics, different kinds of transformer fault status and inrush current influence on differential protection.