When high voltage AC circuit breaker in the power system interrupting the asymmetrical short-circuit current

the transient recovery voltage after the current zero crossing controlled by DC component at the current zero point. Appendix P of‘GB 1984—2014 High Voltage AC Circuit-breakers’ shown the first pole to clear TRV parameter calculation method based on the DC component at current zero point. The medium voltage circuit breaker proceeding test duty T100 a in high power test station is always three phase direct tests

and with first pole to clear factor 1.5 and two parameters TRV. In this paper

the DC component calculation method of the first pole to clear and last pole to clear for major current loop and major extended loop are analyzed and discussed according to‘GB 1984—2014 High Voltage Alternating-current Circuit-breakers’

which can be used to calculate the uc. The research content of this paper can provide the theory and reference basis for prospective TRV parameters calculation for the major current loop and major extended loop.