PD detection in inter-turn insulation of wind turbine generator under induced impulse voltage

The inter-turn insulation of stator winding for wind turbine generator (WTG) usually suffers the repetitive impulse over-voltages when the converter is connected to the winding terminals. The long-term effect of repetitive impulse over-voltages may lead to the development of inter-turn insulation defects and/or the occurrence of inter-turn insulation fault due to partial discharge (PD) activity. In this paper, the detecting method of inter-turn PD in the stator winding of WTG under the induced impulse voltage was investigated. A typical form-wound winding specimen for simulating the inter-turn insulation system of WTG was prepared. An exciting system for inducing high impulse voltage was established. The induced impulse voltage on inter-turn insulations of specimen can be with the peak value up to 1200 V and rise time less than 0.5 μs. The high frequency current sensor with the band width of 1.5∼ 45 MHz was designed for detecting PD activity in inter-turn insulation. The numerically simulating model for this test system was also provided. A series of tests under the different induced impulse voltage levels were carried out in the laboratory. Corresponding to the different induced inter-turn voltages, the output signal of the current sensors were recorded and analyzed. The presently test results indicate that the inducted impulse voltage can excite the PD activity in the inter-turn insulation of specimen.