| Electricity is a basic industry related to the national economy and the people's livelihood.With the development of the national economy and the improvement of people's living standards,the demand for electric energy in today's society is growing.Cable accessories are an important part of the power cable line,and also a weak link.In actual installation and operation,the cable accessories will be affected by the long-term effects of thermal oxygen and mechanical expansion.In this paper,the EPDM rubber for reinforced insulation of cable accessories was studied,and the effects of thermal oxygen on dielectric properties,mechanical properties and microstructure under mechanical stress were studied experimentally.In this paper,the industrial cable accessories are formulated with ethylene-propylene rubber formula.In order to determine the rationality of the formulation design,the effects of different filling concentrations of transformer oil on the mechanical properties of the material were studied experimentally.The results show that the mechanical properties of the material are best when the filling concentration of the transformer oil is 6 phr.On this basis,the effects of temperature and pressure on the dielectric frequency dielectric properties of ethylene-propylene rubber matrix composites were tested.The experimental results show that the temperature has significant dielectric constants for EPDM-based composites under different pressures.Under the condition of pressure determination,the relative dielectric constant of the composite decreases with the increase of temperature,and the loss factor increases with the increase of temperature.Under the determined temperature,the dielectric constant of ethylene-propylene rubber increases with the increase of pressure.The loss factor does not change with increasing pressure.The safe operation of cable accessories is not solely concerned with the basic properties of insulation materials,and long-term aging performance is more important.To this end,the study conducted thermal aging experiments under different conditions of elongation?0%,5%,10%?.The thermal aging temperature was determined to be 125°C,and the dielectric properties of the composite samples were tested after aging for 72 hours,144 hours,216 hours,and 288 hours.The results show that the difference between the low-frequency relative dielectric constant and the high-frequency relative dielectric constant of the composite increases with the aging time,which means that the thermal aging causes the low-frequency relative dielectric constant of the ethylene-propylene rubber to increase.The mechanism is aging.The concentration of polar groups inside the material is increased;the difference between the low-frequency relative dielectric constant and the high-frequency relative dielectric constant of the composite after stretching is greater;the longer the aging time,the DC conductance of the composite The smaller the rate,the order of 10-15S/m,that is,the DC insulation performance is not reduced by thermal aging;the aging time is determined,the larger the strain is,the smaller the DC conductivity of the composite is,that is,the tensile stress.It will affect the DC conductivity of the composite;the aging time and the strain are constant,and the conductivity increases with the increase of the field strength,and it is approximately linear.In addition,mechanical properties of the samples aged under different strains were tested.The results show that the glass transition temperature of the composite increases after 72 hours of aging;the aging time only has a significant effect on the tensile strength of the composite under unstretched and 5%set strain,and the aging time is prolonged.In order to further explore the effects of thermal aging and strain on the internal molecular structure of the composite,the sample was tested by Fourier transform infrared spectroscopy,and the hydroxyl index was used as an indicator to measure the degree of aging.The results showed that aging with the aging time Within 216 hours,the hydroxyl index of the composite increased,and after 216 hours of aging,the hydroxyl index decreased;in addition,the strain was set to increase the hydroxyl index of the ethylene propylene rubber after aging. |
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