Analysis of Harmonic Overvoltage Caused by Inrush Current of Closing No-load Transformer

The excitation inrush current generated by the closing no-load transformer propagates in the power grid, and may cause a temporary overvoltage rise of the bus node after being injected into the system, and the harmonic content is rich. In this paper, the simulation analysis of 500kV and 1000kV typical systems in different system operation modes and different annual modes were carried out, and the suppression effect of measures such as phase selection closing, closing resistance, and adjustment operation mode were studied. The conclusion showed that the phase-selective closing and closing resistors installed in the circuit breaker can reduce the inrush current, but the effect of suppressing such overvoltage was very small. Adjusting the operating mode was the best for suppressing such harmonic overvoltages.