Space Charge Behavior in Crosslinked Polyethylene Degraded by Water Tree

Abstract

The pulsed electroacoustic method (PEA) has been applied to observe space charge formation under AC application (7kV_peak, 50, 0.1 and 0.001Hz) in water-treed polyethylene samples in order to understand the degradation mechanism of water trees. A system with phase-resolved capability has been developed to measure space charge distribution at any phase angle of AC voltage application. By comparing the observed charge distribution with theoretically predicted ones, it has been shown that the interfacial polarization due to the difference in conductivity between the treed and the untreed regions predominates the space charge behavior. It has become clear that the PEA method can be a powerful nondestructive method of evaluating water tree length.