Simulation analysis of distance protection maloperation caused by sympathetic inrush current in transformer

Abstract After the successful startup of the #2 main transformer at the 110kV Ruixia Substation under no-load conditions, the no-load closing of the #1 main transformer caused an incorrect operation of the distance protection, affecting four protection zones. Through theoretical analysis, it was determined that this issue resulted from the sympathetic inrush current. Additionally, a detailed PSCAD electromagnetic transient simulation model was created to further simulate and verify the event. Based on these simulations, a practical and feasible solution was proposed. This paper presents both theoretical and simulation-based analysis of an actual grid event, offering valuable insights for analyzing similar incidents and preventing their recurrence.