In the process of power switching in ultra-high voltage (UHV) substation, the electric shock current of the synchronous condenser circulating water pump will be too large, leading to the situation of multistage tripping. In order to study the switching strategy, the frequency and amplitude of the residual voltage are quantitatively analyzed over time, and relevant simulation studies are carried out. The transient state of reclosing is studied, and the change law of impulse current with time is obtained through simulation. According to the simulation, it is found that the maximum value of the shock current lags slightly behind the point with opposite phase, the minimum value lags slightly behind the point with same phase, and the lag depends on the decay rate of the loss residual voltage. On this bases, a switching method based on the difference between the loss residual voltage and the amplitude of the supply voltage is proposed. The simulation results are analyzed to provide some references for maintenance personnel, so as to reduce the impulse current in the switching process as much as possible and avoid switching failure.