Partial discharge and breakdown characteristics of silicone oil/polymer film composite dielectrics

The partial discharge and breakdown characteristics of polymer-film/silicone-oil composite dielectrics were studied using a needle-plane electrode system. In most of the experiments, DC voltage was applied at 0.5 kV/s until breakdown. Some tests were performed at rates of voltage increase of 1.5 and 3.0 kV/s. It is shown that with the needle positive, breakdown initiates in the oil from the needle tip and the polymer barrier increases the system´s breakdown voltage. With the needle negative, the breakdown of the composite system occurs just after the partial discharge is initiated, indicating that partial-discharge inception is closely related to the breakdown of the composite system. The breakdown voltage is dependent on the negative accumulated charges on the film. These create a high stress across the film and cause breakdown of the composite system