High Frequency Modelling of Stator Windings Dedicated to Machine Insulation Diagnosis by Parametric Identification

This paper presents a novel state-space modelling dedicated to stator insulation diagnosis of form wound electrical machines by parametric identification. The underlying idea of the proposed diagnosis approach is that there exists a wide frequency domain (from several kHz to hundreds of MHz) which has not yet been exploited by conventional electrical diagnosis tools. The originality of our work, but also its difficulty, consists in searching for the best tradeoff between simplicity for model identiflability and complexity for its diagnosis ability. This is important for diagnosis and maintenance procedures which require to interpret the parameter estimated values and theirs drifts. It is possible only if the model parameters are related closely enough to the system physical parameters. A high voltage Mosfet pulse generator with ultra fast rise time allows theoretical and experimental system identification with respect to main industrial constraints. The first experiments deal with coils taken from a 5 kV induction machine. This allows to isolate and understand the complex phenomena which occur in stator insulation during identification procedures.