Research on the Cause Analysis and Suppression Methods for Closing Inrush Current at Low-voltage Side of Distribution Transformers

To address the typical inrush current problem during low-voltage side energization of distribution transformers, this paper analyzes the main causes, including residual core magnetization, closing phase-angle deviation, and current discharge through a low-resistance loop. It proposes suppression methods based on reverse-pulse demagnetization, phase-angle synchronization control, and the configuration of an initial-state current-limiting unit. A 100 kV·A experimental platform is established to acquire waveforms and compare key performance indicators. The test results show that all these methods effectively suppress the peak current and duration. Each method has a clear scope of application and practical value for engineering deployment.