| High voltage direct current(HVDC)transmission technology has the advantages of narrow transmission line corridors,unlimited transmission distance,large transmission capacity,not easily affected by capacitive current,and asynchronous connection between power grids.So HVDC transmission system is attracting increasing attention again due to the good running characteristics and economic value.With the implementation of new energy policies,new energy has been widely used,and flexible HVDC transmission will become one of the most important ways for direct current(DC)power grid.However,in the operation process of XLPE insulated cables,XLPE insulation materials will degrade under the effect of heat for long time,and cause irreversible change on chemical structure and morphology.Therefore,the study on thermal aging properties of HVDC XLPE insulation materials is a hot topic which we should pay attention to at present.This subject has not only important scientific significance but also economic and social benefits,and will promote the holistic development of Chinese cable industry.In this paper,the accelerated thermal aging experiments were performed on HVDC cable XLPE insulation materials under the temperature of 130℃,140℃,150℃.DC breakdown strength,conductivity,space charge,permittivity and dissipation factor,Fourier transform infrared spectroscopy(FTIR),differential scanning calorimeter(DSC),gel content,tensile strength,thermal elongation of XLPE insulation materials were tested under different aging time.The effect of thermal aging on electrical properties,physical and chemical properties,and mechanical properties of XLPE insulation materials was studied.The results showed that the thermal cracking reaction and cross-linking reaction existed at the same time in thermal aging.The cross-linking reaction was dominant at the early stage of thermal aging,and the conductivity properties,space charge distribution,mechanical properties and degree of crosslinking of XLPE insulation materials had no deterioration.With the elongation of aging time,thermal cracking reaction was dominant,and thermal aging had an obvious destructive effect on electrical properties,physical and chemical properties,and mechanical properties. |
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