Mechanical fault diagnosis of high voltage outdoor disconnector based on motor current signal analysis

High voltage disconnector is one of the most widely used switchgear equipment in power system. Mechanical faults caused by improper installation and corrosion of metal components severely affect the normal operation of disconnector. In this paper, various mechanical faults of outdoor disconnector from actual field are displayed and discussed. To diagnose the mechanical fault of motor-driven disconnector, the stator current of driving motor is detected by an acquisition system consist of Hall current sensor, N1 data acquisition card and Lab VIEW software, while the relation equation between motor current and output torque of operating mechanism is derived. The stator current waveforms during switch-on and off process of disconnector are analyzed. The proposed method based on motor current signal analysis has been applied to a 220 kV pantograph disconnector by comparing the characteristics such as peak value and peak time of motor current signals in normal operation situation with the condition of jammed transmission mechanism, that is, simulated mechanical fault. The results indicate that there is a quadratic function relationship between the motor current and the operating torque. The stator current waveform of driving motor may distort when mechanical faults occur on the disconnector. The proposed method of this research work can effectively detect mechanical faults of disconnector thus to improve the reliability of power equipment.