A review on the aging performance of direct current cross-linked polyethylene insulation materials

With the bulge of electrical load for big cities, acceleration of island exploitation strategy and rapid development of renewable energy power generation, the development and application of flexible direct current (DC) power transmission have become an inexorable trend. As a major carrier of flexible DC power transmission, cross-linked polyethylene (XLPE) insulated high voltage direct current (HVDC) cables become more and more important in recent years due to their light weight, good electrical and thermal performance, simple manufacturing process, convenient installation and maintenance in combination with non environmental pollution. The aging of XLPE insulation usually occurs under the effects of such factors as electricity, heat, oxygen, humidity, mechanical stresses, light, chemicals and microorganism encountered in service. It can lead to irreversible damage of XLPE insulation materials, even power accidents, which may bring hidden danger to the operation of power network. In this paper, a comprehensive review is presented on the worldwide research and development related to the aging of XLPE insulation in HVDC cables. The principal factors and mechanisms causing the aging of DC XLPE insulation are also introduced together with the inhibition methods of space charge, which is one of the major components of the aging process in XLPE insulation.