Space charge measurement in polyethylene under high static pressure

Submarine DC power cable engineering is considered as the most difficult and technical transmission project. Accordingly, as the most important part of transmission, submarine cables are equipment with very strict requirement. Polyethylene is widely used in submarine DC power cables as insulators due to its excellent electrical property and mechanical performance. However the problems caused by space charge have kept focusing much attention, which threaten the fatigue life of the insulators. Space charge accumulated in the bulk of dielectric materials may result in local electric stress enhancement and is indicated to play an important role in the degradation and even premature breakdown of insulators for high-voltage application. Considering the extremely harsh undersea environment such as the very high pressure, it is significant to study the space charge behavior on this condition. Thus, in this paper, planar samples are subjected to a high static pressure which is up to 100 MPa and a measurement system based on Piezoelectric Induced Pressure Wave Propagation (PIPWP) method has been developed for monitoring the space charge distribution in the dielectric materials. A precise measurement about the deformation of the sample under pressure also has been done. Results are discussed and it indicated that high pressure have a direct influence on reducing charge injection.