A Feature Set of Electrostatic Field Distribution to Predict Rod-plane Gap Breakdown Voltage

Air gap breakdown voltage is strongly associated with the gap geometry. This paper proposes a feature set of electrostatic field distribution to be equivalent to rod-plane gap structure. A hypothetic fan-shaped feature extraction region was defined between the energized rod and the grounded plane. This region is with a vertical angle at the rod surface, and the outside circular arc is overlapped at the equipotential lines with a certain percent of the applied voltage. Some features were extracted from the fan-shaped region and the shortest interelectrode path to reflect the electrode shape and the gap distance. A SVM model was established to predict the rod-plane gap breakdown voltage, with inputs of the electrostatic field features. After model training with samples selected according to electric field nonuniform coefficient, the SVM model was used for prediction. The prediction results of rod-plane gaps with the rod diameter of 2 cm, 2.5 cm, and 3 cm have high accuracy compared with the experimental data, while the mean absolute percentage error is within 0.0150. The predicted breakdown voltages of rod-plane gaps with the rod diameter of 2.3 cm and 2.8 cm also meet expectation, which demonstrates the validity of the proposed feature set. This method may provide inspiration for air gap insulation prediction studies.