Study On The DC Electrical And Mechanical Properties Of Silicone Rubber At Low Temperature

Silicone rubber insulation material has the advantages of ozone resistance,corona resistance and surface hydrophobicity,et al.Thus,has been widely using in power system.The characteristics of reverse distribution of primary energy and load demand in China demands optimized allocation of energy on a large scale objectivly.HVDC transmission has become an important mean of long-distance cross-regional power transmission,the transmission line may pass through Qinghai,Tibet,Northeast China and foreign "Belt and Road,ect,in these region,the low temperature lasts for a long time and the diurnal temperature difference varies greatly,the DC electrical and mechanical properties of silicone rubber may vary greatly,thus may not meet the higher requirements of HVDC transmission system under the corresponding temperature environment,may cause serious power system accidents,therefore,it is of great significance to study the DC electrical and mechanical properties of silicone rubber insulation before and after alternating aging at low temperature.In order to study the effect of low temperature environment and alternating change of high and low temperature on DC electrical properties of silicone rubber,through the self-built low temperature test platform,between 20? and-60?,before and after alternating aging at high and low temperatures,tested the DC flashover voltage,DC breakdown strength and volume resistivity of silicon rubber samples,with relative content of 90%,110%and 130%aluminum hydroxide.While analyzing the law of variation with the decrease of temperature,compared the data before and after aging.By analyzing the test results,finding that,in the range of test temperature,as the temperature droped,the DC flashover voltage,of which three kinds of Al(OH)3 samples,showed a linear increasing trend,and the DC breakdown strength increased first and then tended to be stable.While the volume resistivity increaseed gradually,satiefied the linear relationship between volume resistivity and temperature of polymer insulating materials.After aging,the DC electrical properties of silicone rubber materials weakeded.and the lower the content of aluminum hydroxide,the greater the effect of alternating changes of high and low temperatures.However,the above three characterizations still increase with the decrease of temperature,but the linear relationship between volume resistivity and temperature in low temperature range was destroyed.Before and after aging,the sample with relative content of AI(OH)3Of 130%had the best electrical properties,and with 90%worst.Considering the effect of low temperature conditions on the mechanical properties of materials,at low temperature,the tensile strength and elongation at break of silicone rubber insulation materials were measured before and after alternating aging at high and low temperatures.The result showed that,between 20 C and-60°C,before and after aging,the tensile strength of silicone rubber insulation increased with the decrease of temperature and the elongation at break decreased.The mechanical properties of silicone rubber were weakened by alternating aging at high and low temperatures,the mechanical properties of the sample with 90%Al(OH)3 content,before and after aging,were the best,and with the relative content of 130%worst.