Space Charge Measurement System for High Hydrostatic Pressure Based on PIPWP Method

Submarine DC power cable engineering is considered as the most difficult and technical transmission project. Polyethylene (PE) is widely used as insulation in submarine DC cables due to its excellent dielectric property and mechanical performance. However, the problems caused by space charge have kept focusing much attention, which threaten the fatigue life of the insulators, and will further affect the insulation performance and service life of the DC cables. For decades, with increasingly mature space charge measurement technology, studies on varies of space charge problems have been done, but space charge behavior in DC cables has rarely been reported under some extreme operating conditions. Thus, in this paper, taking into account the very harsh submarine environment such as extreme pressure, the study of space charge behavior, a special designed setup comprising a Piezoelectric Induced Pressure Wave Propagation (PIPWP) measurement system enclosed with the sample between two steel mold and subjected to high hydrostatic pressure has been developed, which could detect the space charge distribution in the dielectric materials. With this setup, linear low-density polyethylene (LLDPE) planar samples are subjected to a high hydrostatic pressure which is up to 100 MPa. To examine the reliability and validity of this measurement system, the linearity of the peak value in space charge distribution curve applied different voltages with and without pressure are showed and discussed.