Novel Approach to Detect Secondary Arc on Single Pole Tripping Events

For single-line-to-ground faults on critical transmission lines, Single-pole tripping is sometimes utilized to avoid the negative impact of the “unnecessarily” three-phase tripping on power system transient stability. Single-pole tripping is normally followed by a single-pole automatic reclosing to restore the tripped phase and for non-permanent faults, the restoration is successful. However, occasionally, and due to the other two phases being energized, a secondary arc is formed rendering the single-pole reclosing attempt unsuccessful. To avoid such a failed reclosing attempt, and the need for a full three-phase trip and reclose with its dire consequences on the system stability, relay engineers set the dead time delay long enough to account for the typical secondary-arc extinguishing time in addition to some margin. The dead time delay is set based on prior experience with arcing faults on that specific line, or in the utility system where single-pole tripping is applied. In this paper, a novel algorithm to detect secondary arc after single-pole tripping events is discussed. Further, case-studies where this algorithm has been applied are shown. Comparison between this new reclosing function and the traditional method is also provided. The main benefit of applying this method is that, when there is no secondary arc, or when the secondary arc extinguishes relatively fast, a successful reclosing attempt is be made without the need to wait for the static dead time delay setting. Implementing this adaptive approach would lead to fully harvest the benefits of using single-pole tripping since the restoration is achieved as soon as the secondary arc has extinguished leading to a more robust system.