A Noninvasive Interturn Insulation Condition Monitoring Method Based on the Common-Mode Impedance Spectrum of Inverter-Fed Machines

The winding impedance spectrum method becomes popular in online stator insulation monitoring in recent years. It can detect the insulation ageing condition and give alarm before catastrophic failure happens. However, the theoretical explanation of this method is not sufficient and the relationship between impedance spectrum and insulation ageing is not clear. In addition, the existing methods need additional signal injection equipment, which is intrusive and difficult to be applied in industrial applications. Therefore, this article develops a noninvasive interturn insulation condition monitoring method based on the common-mode impedance spectrum in inverter-fed machines. By building a broadband stator winding insulation model, the relationship between the interturn insulation ageing and the impedance spectrum is studied and the high frequency parallel capacitance is first proposed as an indicator for the interturn ageing. The offline test validate the effectiveness of the proposed method and the online test shows the potential of this method for noninvasive condition monitoring in inverter-fed machines. Future work is planned to further improve the online performance of the proposed method.