Contents lists available at ScienceDirect Electric Power Systems Research journal homepage: www.elsevier.com/locate/epsr Determining secondary arc extinction time for single-pole auto-reclosing based on harmonic signatures Iman Nikoofekr, Javad Sadeh ⁎ Department of Electrical Engineering, Faculty of Engineering, Ferdowsi University of Mashhad, Mashhad, Iran ARTICLE INFO Keywords: Single-pole auto-reclosing Secondary arc TT-transform Harmonic signature ABSTRACT In this paper, a new algorithm based on harmonic signatures is proposed to detect extinction of secondary arc for single-pole auto-reclosing (SPAR). In the proposed algorithm, the TT-transform is used to highlight harmonics of healthy phase voltages. The criterion for the detection of extinction of secondary arc is harmonics amplitudes, which is calculated after the TT-transform. The algorithm is noncommunication and the threshold value is adaptive; therefore, for various transmission systems no special adjustment is needed. To evaluate the accuracy of the proposed scheme, numerous simulations under different conditions including fault location, fault in- ception angle and line compensation are performed, in all of which the highest reliability is achieved. 1. Introduction Statistics has shown that more than 80% of faults in overhead lines are of the transient type and, with similar percentage they are single phase to ground faults [1]. Transient faults are caused by lightning or falling of external bodies on the lines; such faults are always associated with arcs [2]. In transmission lines, fault arcs are categorised into two classes, namely primary and secondary. The primary arc happens after inception of the fault, caused by the lightning strike or other reasons, which lasts until the tripping of the faulty phases. On the contrary, the secondary arc occurs after the circuit breakers (CBs) trip as it is sus- tained by the capacitive and inductive coupling between the healthy and opened phases. Single-pole auto-reclosing (SPAR), which means that only the faulted phase is opened, is the most recommended switching procedure to eliminate transient faults. Fundamentally, ex- tinction of secondary arc is the main factor for success of SPAR. In conventional SPAR, the dead time is set to a predefined fixed value, varying from 500 ms to 2 s [3], assuming the arc will extinguish within this dead time. In some cases, the opened phase is reclosed in excessive time because this fixed dead time can be quite large. For short dead time, reclosing can be occurred on an existing transient fault [4]. Generally, to improve reliability of a power system, it is important to reduce dead times and reclose breakers as fast as possible after the arc extinction. Thus, it is crucial to accurately know the exact extinction of secondary arc time. Thus far, several methods are proposed to detect extinction of sec- ondary arc. Spectral energy of high frequency (HF) current and voltage transients are used in Refs. [5] and [6] in order to determine extinction of secondary arc. These methods rely on the capturing of the high- frequency harmonics generated by the secondary arc to determine the moment when the arc extinguishes. During the period of secondary arc, spectral energy is calculated and, when it is less than a threshold value, the arc is assumed to be extinguished. The drawback of these algo- rithms is necessity of high sampling frequency [5,6]. The presented algorithm in Ref. [7] computes the root mean square (RMS) value of the opened phase voltage to detect the extinction time of secondary arc. Here, extinction of secondary arc is indicated when the difference be- tween the present and previous RMS in each time step is greater than or equal to a certain threshold level. However, this algorithm is sensitive to severe changes in voltage signal. The presented algorithm in Ref. [8] detects extinction of secondary arc based on calculating low frequency components of the opened phase voltage waveform. In this method, a harmonic distortion index (HDI) is introduced and the extinction time of secondary arc is detected by comparing a suitable threshold value and HDI. In Ref. [9], differential protection principles, which are ap- plied to the zero sequence power at both ends of the line, are used to identify the extinction time of secondary arc. However, this scheme requires communication channels at the line terminals. In Ref. [10], the total harmonic distortion (THD) value of the opened phase voltage is obtained and it is shown that after extinction of secondary arc, the THD has a great decrease. This scheme is not applicable for compensated transmission lines. The presented scheme in Ref. [11] uses current and voltage phasors at both ends of the line. The presented algorithm cal- culates the angle of post-fault arc voltage at the measurement point after the CB is opened and, if this angle is less than a threshold, the secondary arc is extinguished. In Ref. [12], the third harmonic of the https://doi.org/10.1016/j.epsr.2018.06.013 Received 3 November 2017; Received in revised form 15 May 2018; Accepted 21 June 2018 ⁎ Corresponding author. E-mail address: sadeh@um.ac.ir (J. Sadeh). Electric Power Systems Research 163 (2018) 211–225 0378-7796/ © 2018 Elsevier B.V. All rights reserved. T