High Frequency Performance of Nonlinear Stress Grading Systems

This paper presents the results of numerical simulation and analysis of the characteristics of stress-grading systems of high voltage rotating machines against frequency. A lumped circuit model was developed to model stress-grading system. The parameters of stress-grading systems are optimized to minimize the local electric field enhancement at a set of discrete operating frequencies. The nonlinear stress-grading resistances are updated in response to the dynamic change of the local surface field compared to the desired average field. The model allowed for fast and accurate design and analysis of nonlinear stress-grading systems with the deviation of the highest local field from the desired average field kept very low. Simulation examples and several optimal stress-grading system characteristics are also presented.