Risk of Winding Insulation Breakdown in Large AC Motors Caused by Steep Switching Surges Part 1 Computed Switching Surges

The research reported here and sponsored by the Electric Power Research Institute was initiated to demonstrate the applicability and use of the finite element method for probabilistic assessment of the risk of turn insulation breakdown in large AC motors. Computer models were developed for computation of the electromagnetic transients in the AC motor windings. Mathematical models were developed to compute the risk of turn insulation breakdown. The application of the proposed approach was demonstrated for a typical installation. This allowed evaluation of the advantages of using the finite element method in terms of accuracy, efficiency, capability and limitations. It also identified the need for further research to facilitate the use of this risk assessment method by utility engineers.