Modification of Permanent Magnet Synchronous Motor Drive Mechanism of SF6 HVCBs of 330/132kV Transmission Substation

This paper presents an improved drive mechanism for Sulphur Hexafluoride (SF6) High Voltage Circuit Breakers (HVCBs) deployed in 330/132kV transmission substations. The proposed system replaces the conventional servo-based permanent magnet synchronous motor (PMSM) with a stepper motor–based PMSM configuration to overcome challenges associated with inadequate holding torque and delayed tripping response. The modified drive mechanism was modeled and simulated using MATLAB/Simulink. Simulation results indicate that the proposed system delivers a peak torque of 120 Nm using a 10:1 gear reduction ratio, exceeding the required breaker load torque of 75 Nm. Furthermore, a reduction in tripping time of approximately 25% was achieved, demonstrating improved fault-clearing performance. The proposed mechanism enhances operational reliability, torque stability, and efficiency of SF6 HVCBs in high-voltage power systems.