A method to diagnose the property of single-phase fault on high-voltage transmission lines

The key point of adaptive reclosing technique is distinguishing permanent fault and transient fault reliably and immediately. Shunt reactors with a small reactance in the neutral point has being widely used in the transmission system so that it can make sure the arc extinguished occurs in fault point as soon as possible and keep the recovery voltage amplitude in a low level, finally, has a higher success rate of the single phase reclosing. According to the transient fault characteristics on high voltage transmission line, The impact of shunt reactor on each component of recovery voltage is analyzed, it gives the generation mechanism of the beat frequency phenomenon in recovery voltage, what´s more, the calculation formula of beat period is deduced. There gives the envelope´s equation by structuring the envelope in use of the basis of the recovery voltage´s extreme point; According to the distinction in the envelope slop between two different faults, this paper put forwards a new approach in distinguishing the fault´s nature based on the envelope slope. A large number of ATP simulations verify, the new method is feasible, which has the advantage of high reliability, short time of judgment and a strong practicability.