Fault nature identification for single-phase adaptive reclosure on double circuit EHV transmission lines with shunt reactors

Abstract

The double circuit EHV transmission lines have been widely used because of its many advantages. But when faults occur, the style of fault and the operation condition are more complicated than that on the single circuit transmission line. The faults occurred on the transmission lines is mainly transient fault. The auto-reclosure is normally applied after the fault line tripped to improve the power supplies reliability and the power system safety. But if the fault is permanent and the auto-reclosure reclosed accordingly, the power system and its apparatus will suffer short circuit current again, resulting further damage of the equipment and making power system instability. Thus, it is very important to distinguish the transient and permanent fault before the tripped fault line auto-reclose. If the EHV line has shunt reactor, identification of fault nature becomes even more difficult. There are several methods proposed for distinguishing the transient and permanent fault but mainly for single circuit transmission line. In this paper, a novel method is proposed for the EHV double circuit transmission lines with shunt reactor. After tripped, the phase voltage across shunt reactor was calculated using our established transient fault line model regardless of the fault is transient or permanent. The difference between the calculated voltage and the measured voltage of the fault phase across shunt reactor was employed to identify transient or permanent fault. The amplitude ratio, i.e. the difference of the voltage between calculated and measured to the voltage across neutral reactor was used to judge fault nature. If the amplitude ratio is greater less than 1, the fault is regarded as transient. If it is more than 1, it is regarded as permanent. This result can be further verified by EMTP simulation.