Propagation of creepage discharge on solid insulator in insulating oil

In relation to the optimum design of internal insulation for HV oil-filled power apparatus, studies of the creepage discharge on the surface of a solid insulator in insulating oil are of practical importance, so much research on this subject has been carried out. In the present paper, the propagation aspects of a creepage discharge on a hard glass (thickness: 3 mm) in insulating oil such as transformer oil are observed in detail under an impulse voltage condition in a point-plane electrode geometry, by using a high-speed schlieren method. In addition, turning our attention to a surface state of a pressboard, the creepage discharge on it is investigated by using a video camera and an image-fiber observation system.