Research On The Influence Of Crosslinking Agent And Antioxidant On The Performance Of XLPE Insulation Materials

Compared with the oil-paper insulation,cross-linked polyethylene（XLPE）insulation material has significant advantages in the application of power cables.In the future,XLPE cables will be mainstream in power cables.The research and development of XLPE insulation materials for high-voltage AC cables in our country is relatively late,and the domestic 220 kV voltage-grade insulation materials have not yet been used in engineering.Cleanliness,the limitation of impurity content,is the prerequisite to ensure high insulation strength.Therefore,while ensuring sufficient cross-linking reaction sensitivity and cross-linking degree of polyethylene（PE）,minimize the amount of cross-linking agent to reduce the output of by-products,thereby improving the cleanliness of XLPE.Meanwhile,different antioxidants and their contents have different effects on the electrical properties,thermal properties and mechanical properties of XLPE cable insulation materials,as well as different resistance to heat and oxygen aging.Therefore,the optimal content of the crosslinking agent dicumyl peroxide（DCP）and the type and content of antioxidants are crucial to the research of high-voltage cable insulation materials.This article first used PE as the base material,added different mass parts of crosslinking agent DCP and 0.3 phr antioxidant 300 to prepare XLPE insulation materials.And studied the effect of crosslinking agent content on the degree of XLPE crosslinking,crosslinking reaction time,by-product gas output,mechanical properties and electrical properties,and compared the properties of XLPE insulation materials with imported high-voltage AC cables.So as to get the crosslinking agent content with excellent comprehensive performance of XLPE.The experimental results of crosslinking characteristics showed that as the content of DCP increases,the degree of cross-linking and the rate of cross-linking reaction of XLPE increased.But when the DCP content increased to 1.8 phr,the degree of crosslinking and the rate of crosslinking reaction increased slowly.The gas production measurement value showed that with the increase of DCP content,the gas production gradually increased.Therefore,in order to ensure good degassing efficiency,the degassing time should be at least 24 h.The tensile strength test results showed that with the increase of DCP content,the tensile strength and elongation at break increased obviously.The AC breakdown strength and dielectric spectrum results showed that the breakdown strength and dielectric constant of XLPE insulation materials with more than 1.7 phr of DCP had little difference and good dispersion,which is similar to imported XLPE insulation materials.Even at high temperatures,the attenuation rate was lower than that of imported XLPE insulation materials,but the dielectric loss in the high frequency range was slightly higher than that of imported XLPE insulation materials.The results of accelerated thermal aging test and oxidation induction period test at 168 h and 135 ℃showed that the XLPE insulation materials with 1.8 and 1.9 phr DCP had better thermal aging resistance,and the growth rate of carbonyl index was lower.Considering the overall consideration,the added amount of DCP was selected as 1.8phr.Then,on the basis of 1.8 phr DCP,different mass parts of antioxidant 1010 and antioxidant 1035 were added to prepare XLPE insulation materials.The effect of the type and content of antioxidants on the electrical properties and heat aging properties of XLPE insulation materials was studied,and XLPE insulation materials for highvoltage AC cables with excellent comprehensive performance were obtained.The cross-linking characteristic experiment found that the cross-linking time of the XLPE insulation materials of the combination system of antioxidant 1010 and antioxidant1035 was longer than that of the XLPE insulation materials of a single antioxidant system.It showed that the combination of two antioxidants would have a synergistic effect.Antioxidant 1010,as a low-efficiency antioxidant,provided hydrogen atoms to the free radicals generated by high-efficiency antioxidant 1035,and regenerated them into high-efficiency antioxidants.At the same time,the low-efficiency antioxidant free radicals formed could also be combined with peroxides.Thereby strengthening the overall inhibitory effect of antioxidants.The AC breakdown strength and dielectric spectrum results showed that,except for the XLPE insulation materials with 0.3 phr antioxidant 1010,the breakdown strength and dielectric constant were not much different,and the dispersion was good,which was similar to imported XLPE insulation materials.In the aging experiment,the growth rate of the carbonyl index of the two compound systems was lower,which further showed that the synergistic effect of the two antioxidants could better inhibit aging.Therefore,the antioxidant addition was selected as 0.15 phr antioxidant 1010/0.15 phr antioxidant 1035.In general,the system of 0.15 phr antioxidant 1010/0.15 phr antioxidant 1035/1.8 phr DCP had excellent comprehensive performance.