Effect Of Thermal Aging On Electrical And Mechanical Properties Of HVDC Cable Cross-linked Polyethylene

With the progress of the times,HVDC plays an more and more important role in the construction of the State Grid,at present,the development of HVDC technology has become the trend of the construction of power grid.In order to adapt to the transmission of urban and offshore environment,high-voltage power cable has become an indispensable and important equipment in the transmission system.Cross-linked polyethylene(XLPE)has been generally used as the high-voltage direct-current cable insulation materials and it has become indispensable part in the HVDC cable today because of its light weight,simple manufacturing process,easily installation,excellent electrical performance,good heat resistance,easily operation and maintenance advantages.The shelf life of the general XLPE power cable is designed to be about 60 years,but the realistic shelf life of the cable is always less than expected because of the influence of the ambient conditions and the magnitude of the load current.Under the combined effect of the electrical stress,thermal stress,mechanical stress and environmental stress,the XLPE cable will gradually aging and deteriorate which will affecting the functions of the cable.And based on the structure of the cable,cable shielding materials and XLPE material will bond together closely,this physical structure has some difference with the single cross-linked polyethylene material phase on its electrical performance.The study on the influence of thermal aging on the insulation materials of HVDC cables and the effect of cable shielding materials on insulation materials after thermal aging are not enough until now.In order to study the change of the electrical properties and mechanical properties during the aging process of the XLPE cable,understand the effect of semiconductor cable shielding material to the cable's electrical properties during the aging process,this article launch accelerated ageing experiments on three kinds of XLPE cable insulation materials:domestic 100kV,domestic 320kV and borealis 500kV.The experimental results show that the performance degradation of resistance properties,dielectric properties space charge properties,mechanical tensile properties of the XLPE is enhanced with the increase of aging time under the thermal aging condition,degradation rate is faster with the increasing of the temperature,during the aging process,domestic 320kV shows the optimal thermal setting,resistance performance and mechanical tensile properties,domestic 100kV shows the optimal electrical properties,the borealis 0550 shielding material shows better performance in space charge resistance with three kinds of XLPE with performance than the borealis 4401 shielding material.Through the experimental analysis on the difference of the mechanical and electrical properties of different insulation materials during the process of accelerated aging experiment and the impact which the cable shielding material acting on the XLPE insulation material,the article provide a more authentic and credible consultation on the decrease of the service life and the speed of the performance degradation of the XLPE cable insulation material during the realistic operation.