| High voltage direct current?HVDC?transmission has the advantages of long-distance,large-capacity,low-loss,that is listed as a key development direction in the national"Thirteenth Five-Year Plan".As a result,the state has great demand for HVDC power cables and their accessories,which means that their research and development have important engineering value.It has been found that cable faults always occur in the insulation part of cable accessories.In this paper,first of all,the influence of the property of the reinforced insulation on the electric field distribution of the cable termination has been analyzed by the simulation software,and then the basic experiment of formula of ethylene propylene diene monomer?EPDM?rubber for the cable termination has been carried out.In order to find out the influence of the property of reinforced insulation on the electric field distribution of HVDC cable termination,the 320kV HVDC cable composite termination has been selected as the research object,and the property of insulation has been used as research elements.Influence of material coefficient,the dependence coefficient of electric field and the thermal activation energy on the steady and transient electric field of cable termination have been separately studied.The simulation results show that in the electric field of the cable termination,there are mainly three sensitive positions,the root of the stress cone,the end of the reinforced insulation and the top of the stress cone.Under the conditions given in this paper,when material coefficient is 5.39×10-3V/???m2?,the dependence coefficient of electric field belongs to the 1.506.00×10-7m/V and the thermal activation energy is0.23eV,the electric field distribution of cable termination is better.Based on the results of the simulation study,the possible ways of regulating the material properties of EPDM rubber were experimentally explored.In this study,single component nano-carbon black?CB?,micron-sized SiC,two-factor nano-CB,and micron-sized SiC were added to the EPDM rubber matrix to prepare nanocomposites.The direct current?DC?conductivity were tested,and the DC conductivity data measured at different temperatures and field strengths was fitted and the dielectric spectrum of the composite material was tested at the same time.The experimental results show that material coefficient decreases first and then increases slightly,the dependence coefficient of electric field increases and the thermal activation energy decreases first and then increases,with the increase of single-factor nano-CB filler;material coefficient is greatly reduced,the dependence coefficient of electric field gradually increases,and the thermal activation energy gradually decreases,with the increase of single-factor SiC filler;1.5 copies of nano-CB and two-component addition of 1.5 copies of nano-CB and 20 copies of SiC added to EPDM rubber have similar fitting parameters of conductivity,that is,Nano-CB plays a leading role in two-components.Although the ideal EPDM rubber has not been found in the experimental study,it laid a certain experimental basis for the control of material properties. |
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