Single-phase permanent fault detection for reactored EHV/UHV transmission lines

Present single-phase reclosure in ultra-high-voltage (UHV) and extra-high-voltage (EHV) transmission lines normally using a dead reclosing time may aggravate severe damage to the system and equipments, for unsuccessful reclosure in permanent fault or insufficient transient fault. Thus, it is important to study on the single-phase permanent detection technique aiming to lower unsuccessful reclosing rate and meet the increasing requirement on self-healing ability in smart grid. After the energy transmission channel between the sources and the faulted phase are cut off by the breakers at two terminals, the open phases in permanent fault and transient fault are considered as internal fault and external fault respectively for the differential current relaying protection. Therefore, a singlephase permanent fault identification criterion is proposed based on the differential current principle with distributed capacitance current compensation in time domain. ATP simulations show that the developed criterion is of higher sensitivity and reliability and it is promised to apply on the EHV and UHV transmission lines with two-terminal shunt reactors.