Analysis of the Application of Single-Pole Auto-Reclosing on 70 kV Transmission Networks Using High Resistance Grounding
Abstract
Single-phase-to-ground faults are the most common disturbances in 70 kV transmission systems and are generally temporary. However, the continued use of Three-Pole Auto-Reclosing (TPAR) causes all phases to be disconnected even when only one phase is affected, which reduces system reliability and continuity of supply. This study evaluates the application of Single-Pole Auto-Reclosing (SPAR) in a 70 kV transmission network employing a High Resistance Grounding (HRG) scheme through comprehensive simulations that consider Critical Clearing Time (CCT), power surge characteristics, and secondary arc behavior under various operating conditions. The results demonstrate that SPAR can improve system recovery and maintain transient stability during temporary faults. Nevertheless, high overvoltage observed in certain transmission lines produces significant generator oscillations, which limits the applicability of SPAR in those sections. The results show that CCT values ranged from 224 ms to more than 5 s depending on fault location, indicating sufficient transient stability margins. Secondary arc currents were observed in the range of 1.2–1.77 A, significantly below the typical extinction threshold of 20 A, suggesting a high probability of successful arc extinction. However, power surge analysis revealed critical limitations leading to significant generator oscillations. As a result, SPAR was found to be feasible for only 1 out of 5 transmission lines, while the remaining lines were restricted due to excessive transient response. In addition, the performance of SPAR is strongly influenced by the successful extinction of secondary arcs and proper coordination of Directional Ground Relay (DGR), where the relay acts as a comparator to distinguish between unbalanced load conditions and actual ground faults. Therefore, the implementation of SPAR in HRG-based 70 kV systems must be carried out selectively by considering system stability, overvoltage limits, and protection coordination to ensure reliable and secure operation.