Research on tripping and reclosing strategy and quasi-three-phase operation of double circuit lines on the same tower

Conventional protection of double-circuit lines on the same tower trip and reclose the two circuits independently after transmission line faults. The possibility of tripping all lines is high when inter-circuit faults occur. Large amount of load will be rejected and electrical link between two sides will be disconnected. It has negative effect on the stability of the power system. The paper proposes a novel tripping and reclosing strategy which regards the double circuits as a whole. It can decrease the possibility of tripping all lines and reclosing to permanent faults. According to the proposed strategy, the double circuits can transfer into the Quasi-Three-Phase Operation (QTPO) which remain at least one line of each phase after faults. The paper researches and analyses the feasibility of QTPO. A typical model of double circuit lines on the same tower is built in PSCAD/EMTDC. Some important electrical indexes which can reflect the performance of QTPO are analyzed by simulation. The results show that QTPO is feasible. The proposed scheme is benefit to the stability of system and satisfied the requirement of power industry operation.