Application of single phase tripping and re-closing to 380KV double circuit transmission line

Faults within a transmission system can greatly impact the capability for power transfer. Isolating a fault by removing the line from service can further diminish the power transfer capacity, compromising the system`s stability margin. Single-phase-to-ground faults, which are the most frequent, can be effectively isolated by taking only the affected phase out of service, while keeping the remaining two phases active. This approach, referred to as single-pole switching (SPS), permits the line to carry two-thirds of its power and preserve synchronization between the sources at both ends of the line, However, it presents distinct challenges. In a long line, a small AC current can still sustain even after the breakers open. This current is called the secondary arc current and it is due to electromagnetic coupling between the phase conductors. If the breaker pole is reclosed before this current extinguishes, the fault will reoccur, leading to unsuccessful reclosure. The aim of this work is to identify the key factors that significantly influence the secondary arc current and to evaluate different methods to reduce its amplitude. For successful reclosure, the circuit breaker`s dead time must be longer than the secondary arc`s extinction time. This study models the secondary arc using the EMTP program to simulate its interaction with the transmission system and estimate the necessary dead time for the circuit breaker. The study analyzes the self-extinguishment of the secondary arc by monitoring its magnitude and the recovery voltage using EMTP. It concludes with recommendations for reducing the secondary arc current and determining the minimum dead time required for the successful reclosure of a 380KV transmission line.