The Use of Cable System Models for the Assessment of Space Charge Behaviour in Full-size DC Cable Systems

Through the years, space charge measurements have shown to be instrumental for the development of extruded-type DC cable systems. However, since performing space charge measurements on full-size components presents major technical difficulties, tests are often done on models of the cable system. This paper assesses the validity of using models of cable systems for the evaluation of space charge in the full-size objects. For this purpose, space charge measurements were performed on specimens of increasing complexity, i.e. mini-cables, dual-dielectric mini-cables, MV-size cables and MV-size models of cable joints. Space charge patterns of the different types of specimens were compared and discussed. In this way the effect that the size and the type of test object have on space charge behaviour was investigated. It was observed that, in some cases, the space charge accumulation is very sensitive to a variation of the specimen complexity, in particular at interfaces between two different dielectrics.