One Terminal Digital Algorithm for Adaptive Single Pole Auto-Reclosing Based on Zero Sequence Voltage

This paper presents an algorithm for adaptive determination of the dead time during transient arcing faults and blocking automatic reclosing during permanent faults on overhead transmission lines. The discrimination between transient and permanent faults is made by the zero sequence voltage measured at the relay point. If the fault is recognised as an arcing one, then the third harmonic of the zero sequence voltage is used to evaluate the extinction time of the secondary arc and to initiate reclosing signal. The significant advantage of this algorithm is that it uses an adaptive threshold level and therefore its performance is independent of fault location, line parameters and the system operating conditions. The proposed algorithm has been successfully tested under a variety of fault locations and load angles on a 400KV overhead line using Electro-Magnetic Transient Program (EMTP). The test results validate the algorithm ability in determining the secondary arc extinction time during transient faults as well as blocking unsuccessful automatic reclosing during permanent faults.