Propagation of Electrical Tree in Extended Chain Crystal Polyethylene

Abstract

Extended chain crystal(ECC) polyethylene exhibits some unique properties. It is possible to make transparent highly crystallized polyethylene in the ECC phase. Electrical treeing discharges were investigated using a needle to plate electrode system under an application of lightning impulse voltage. The propagation of trees was observed using a high-speed image converter camera. The formation of tree channels was a very rapid phenomenon, 1μs. The discharge current accompanying the trees consisted of two kinds: A large current pulse, occurring just after voltage application, appeared to be a combination of injection current and charging current. Immediately following this large pulse, small current pulses appeared intermittently in the wave tail of the applied voltage. It is thought that these small current pulses are attributable to the rearrangement of charges in the gas phase on the inside surfaces of tree channels.