High-voltage dc insulation and space charge

Recently, much attention has been paid to the HVDC power transmission systems, especially in long-distance power transmission and submarine power cables. The developments of high-performance HVDC power apparatus and cables have been required. However, there are some problems unsolved in HVDC insulation. One of them is space charge behaviour. An understanding of space charge behaviours in solid insulating materials is necessary for the successful design of HVDC insulating systems. In this paper space charge behaviours in various solid insulating polymers measured with new non-destructive techniques such as the LIPP, PEA and TP methods are reviewed and discussed. They are very sensitive to the physical/chemical structures of insulating polymers, additives, interfaces, electrode materials, ageing, applied field, temperature and so on. The effects of space charge on the DC performance of insulating materials are discussed quantitatively. Some suggestions for improving HVDC insulating materials and, as a result, HVDC power apparatus and cables are given.