In this paper the DC omponent in current of circuit breaker during transmission line energizing is analyzed.The impact of closing phase

compensation degree and closing resistors of circuit breaker on the amplitude of DC component are discussed.And measures which could be taken to prevent the failure risks of circuit breakers caused by DC offset are also studied.Phase control technology is chosen as the most feasible measure on the base of comparison of the applicability of all the measures

which include phase control breaker closing

reducing compensation degree and addtion of closing resistors.The application of phase control technolgy on the prevention of DC offset is studied.The phase control strategy of breaker closing

and the monitor variable for adaptive feedback regulation are disscussed.The impact of application of phase control on operationg overvoltage is also analyzed by simulation with PSCAD/EMTDC.The effectiveness of phase control breaker closeing on DC offset prevention is valided by field test on a typical transmission line.The impact of mechanical dispersion and pre-breakdown between contacts of circuit breakers are discussed on base of the test results

and the applicability of phase control is also analyzed.