Calculation and Error Range Analysis of Residual Flux in No-Load Transformer Phase Selection Closing Based on Voltage Integration Method

The magnetizing inrush current caused by the no-load closing of a transformer may lead to secondary side maloperation and cause damage to the mechanical structure of the transformer. Currently, the phase selection closing technology based on residual flux calculation can theoretically eliminate residual flux, making the calculation of residual flux particularly important. Due to inevitable noise, drift, and other interferences in the collected voltage signals, the residual flux obtained through the voltage integration method has certain errors. Based on the voltage integration method, this paper proposes an error analysis method for magnetizing inrush current under a phase selection closing strategy. Experiments on the opening and closing of a single-phase transformer were conducted, and the errors in magnetizing inrush current caused by phase selection closing under residual flux errors were analyzed.