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.<>