Characteristics of commutation failure based on fault recording

Commutation failure of the high‐voltage direct current (HVDC) transmission system is common fault in a converter station. The fault recording in one converter station when commutation failure caused by the disturbance of the AC system was collected, and the turn‐off angle of valves, zero‐crossing offset, and landing amplitude of bus voltage were calculated and statistically analysed. The results suggested that, in the case of commutation failure, the turn‐off angle of the 82% of cases was <8°, and there were a few cases whose turn‐off angle was very nearly the same as that in normal operation. The number of cases whose zero‐crossing offset was <10° accounted for 95% of the total, and the zero‐crossing offset of the AC bus line voltage generally presented a positive correlation with the reverse cut‐off time of the valves. The landing amplitude of the AC bus voltage before the time point for commutation failure analysis fall within 10% for >90% cases, and the average was ∼4.6%. The number of cases, whose zero sequence voltage peaks was <50 kV, accounted for 97% of the total. The results will provide basic data for analysing the main influencing factors of commutation failure and setting up countermeasures for the HVDC system.