Abstract
Creeping impulse discharges occurring at the insulating systems of electric power equipment are significantly af-fected by the presence of a surrounding grounded metal case. Using a standard lightning impulse voltage, the characteristics of creeping streamers were studied over the surface of an oil-immersed polyethylene (PE) insulated wire with a grounded side electrode. The discharge characteristics (discharge aspect, streamer extension length, streamer current and charge, etc. ) were measured as a function of the distance between the PE wire and the grounded side electrode. Streamer polarity and the position of the side electrode significantly affected both streamer generation and propagation. The creepage characteristics were also examined using two methods of voltage application. Differences in the test results of each method were attributed to the position of the side electrode. The potential distribution inside the streamer channel and the streamer propagation velocity were measured by means of a potential probe. Streamer velocity was found to be constant and the streamer channel was not equipotential.
