Multi-objective parameter optimization of shunt reactors for multi-circuit transmission lines on the same tower

The electromagnetic coupling between the transmission lines on the same tower brings significant impacts on the secondary arc behavior, which results in requirement for re-optimization of the shunt reactors and the neutral reactor. Equations for calculating the secondary arc current as well as the recovery voltage were developed through establishing distributed parameter-based electromagnetic coupling model for the multicircuit transmission lines, based on which the key factors influencing the secondary arc current and the recovery voltage were investigated. A dynamic secondary arc model for UHV transmission lines was adopted to account for the impacts of the initial arc length, the neutral reactor and the compensation rate of the shunt reactors on the secondary arcing time, and the differences in parameter optimization of the neutral reactors under single circuit and multi-circuit were discussed. Resonance frequency analysis was applied regarding the resonant overvoltages caused by unbalanced switching operations as well as by electromagnetic induction between circuits, with a view to deducing simplified formula for the inherent resonance points which could easily be extended to the multi-circuit transmission lines and indicated that the shunt reactors and the neutral reactor required re-optimization specifically for multi-circuit transmission lines. The research results present useful reference for optimal design of the shunt reactors and the neutral reactor in EHV/UHV double-circuit as well as multi-circuit transmission lines on the same tower.