Space charge measurements on power cable length

The set up of nondestructive techniques for measuring space charge has allowed to prove the importance of these charges on the longtime behaviour of cable insulation. It seems today more and more probable that the decrease of performance and breakdown of polyethylene-insulated power cables are related to the appearance and the development of space charges. In this work, we show how one can, using the Thermal Step Method (TSM), to evaluate the electrical state of a significant cable length, both locally and globally. We also compare the charging ability of a cable insulation after two types of applied stress: poling at room temperature and under a thermal gradient similar to the one which appears in cable during operation.