Electrical tree propagation in composite insulation for wind turbine generator under repetitive impulse voltage

摘要

The insulation system of wind turbine generator (WTG) would subject to repetitive impulse voltage due to the application of inverter unit. The electrical tree propagation is one of the major causes of breakdown. In this paper, it is the main focus that how the different barrier materials in the composite insulation system influence the electrical trees propagation under the repetitive impulse voltage. The glass fiber, mica powder tape and polyimide film were respectively chosen as the barrier materials. For each kind of samples, the propagation tests of the electrical trees under repetitive impulse were carried out. It was found that the electrical tree showed the branch feature, and when it reached the barrier, its branch increased and expanded along the barrier interface. After a long duration of stagnation, the electrical tree developed rapidly, and finally the breakdown occurred. The expansion distance of tree branch for the samples with polyimide film barrier was longest. The stagnation duration of the samples with the mica powder tape barrier was longest, and then that of the samples with glass-fiber tape barrier was shortest. The mechanisms of feature differences between them might be explained by the bond energy between the epoxy resin and barrier, and the dielectric strength of them composite insulation. Also the inception time and growth rate of the electrical tree between samples with three barrier materials performed the little diversity.