An Online Groundwall and Phase-to-Phase Stator Insulation Monitoring Method for Inverter-Fed Machine

Inverter-fed machines are widely used in industrial applications. In inverter-fed machines, the insulation ageing is accelerated due to the high dv/dt and transient overvoltage. Therefore, it is necessary to develop effective online monitoring methods for stator winding insulation to ensure the reliable operation of inverter-fed machines. In this article, a novel nonintrusive online monitoring method is proposed to monitor the stator insulation, which can be used to give alarms for the potential failures. The proposed method measures the phase-to-ground voltages and leakage currents to calculate the capacitance of the insulation using multifrequency information. Compared to the existing monitoring methods, the proposed method is the first method, which can monitor the phase-to-phase (PP) and groundwall (GW) insulation capacitance separately. It largely improves the sensitivity on the PP insulation monitoring and realizes the GW insulation monitoring in the same time. The proposed method is validated on an inverter-fed machine in the lab. Online and offline results are compared to validate the proposed method. The simulated insulation ageing experiment shows that the proposed method can detect incipient insulation ageing with high sensitivity.