There is a large DC offset in the charging current after closing operation at one side of the no-load overcompensated line

which makes the charging current have no zero-crossing point for a long time.During this period

unexpected opening of the circuit breaker may cause the arc can not be extinguished even the breaker reaches its mechanical breaking point.Based on the analysis of the mechanism of DC offset

this paper proposes a phase angle control and self-adaptive delay sequential closing method for the first time

which combines the phase control closing technology and the charging current zero-crossing point detection technology

and solves the problem of arc-breaking in AC circuit breakers when the current is not zero-crossing effectively.Based on this method

the self-adaptive phase control and dynamic time-delayed sequential devices is developed and tested on three 500 kV over-compensation lines of Hebei south power.The dispersion of closing of 500 kV circuit breaker

the control precision of phase selection closing mode and the restraining effect on DC offset component are summarized in this paper.The engineering test shows that this method can effectively reduce the risk of DC offset after the no-load over-compensated line is closed.