Influence Of Pressure On Dielectric Strength Of Silicone Rubber For HVDC Cable Accessories Reinforced Insulation

DC cables and DC cable accessories are important parts of HVDC transmission,it's important for operational stability of HVDC transmission systems to reduce their failure rate.Due to the differences in temperature and field strength of the main insulation cross-linked polyethylene and reinforced insulation silicone rubber in HVAC accessories,as well as the effect of enhancing the pressure between the insulation and the main insulation,the cable accessories become the weakest link in the HVDC transmission system.In order to study the influence of pressure on the electrical strength of silicon rubber,the insulation material of cable accessory,this paper took pure silicone rubber and composite silicone rubber with nonlinear conductivity as the research object,tested 0.10 MPa,0.15 MPa,0.20 MPa,0.25 MPa,0.30 MPa pressure and 30 ?,50 ?,70 ? temperature breakdown characteristics of the two silicone rubber and cross-linked polyethylene / silicone rubber surface flashover characteristics of the interface;compared the different influence on dielectric strength between pure silicone rubber and non-linear silicone rubber,and according to the actual working conditions of the cable accessories,the silicone rubber samples were heated for 150 h,300h,450 h,600h and 750 h respectively at the temperatures of 90 ?,110 ? and130 ? while maintaining the pressure of 0.10 MPa,0.20 MPa and 0.30 MPa.The effects of different aging pressures,aging temperature and aging time on the breakdown characteristics of silicone rubber were tested.The results show that with the increase of pressure,the breakdown field strength of pure silicone rubber and non-linear silicone rubber decreases gradually.Compared with pure silicone rubber,the breakdown strength of nonlinear silicone rubber decreases more quickly under the same pressure.The flashover voltage of cross-linked polyethylene / pure silicone rubber and cross-linked polyethylene /non-linear silicone rubber interface increased as the pressure increased,and the flashover voltage of cross-linked polyethylene / non-linear silicone rubber interface increased faster.After thermal aging,the breakdown strength of silicone rubber increases first and then decreases with the increasing of aging time.Under the condition of constant aging pressure,the higher aging temperature,the smaller breakdown strength of silicone rubber is.When the aging temperature is constant,the more aging pressure,the weaker breakdown strength.