Correlation between space charge distribution under DC voltage and dielectric breakdown properties in XLPE under impulse voltage superposed onto DC voltage

Describes breakdown tests under DC long term application measuring space charge in XLPE. The time transition of space charge showed that dielectric breakdown cannot be explained by only the local maximum electric field in the bulk, but should be considered as the deterioration of insulating material caused by the increase of carrier density. In order to make a rational insulating design method for DC XLPE cables, space charge distribution immediately before dielectric breakdown under impulse voltage superposed DC voltage is studied. Correlation between the space charge distribution immediately before dielectric breakdown by DC impulse superposed voltage and the dielectric breakdown strength are discussed in this report.