Simulation And Analysis Of Electrical Field Distribution Of XLPE Insulated DC Cables Terminal

High voltage direct current(HVDC)transmission has become an important development direction of high voltage transmission because of its low loss,high reliability,large carrying capacity,and suitable for long distance transmission.The reliability of the cable system is an important prerequisite for the stable operation of the power grid,and the cable terminal is an important part of the cable system.But compared with the cable as a whole,the failure rate of the cable terminal is higher.The main reason is that the electric field strength endured by the cable terminal is much higher than the average value of the overall electric field strength.Thus it is significance to research the electrical field distribution in the cable terminal and obtain efficient ways improvi ng electrical field distribution.In this paper,110 kV HVDC cable composite terminal is chosen as the research object.Firstly,the stress cone curvature of 42 mm,48mm and 54 mm curvature is taken as the research factor,and the electric field of stress co ne surface,enhanced insulation and XLPE insulation layer under polarity reversal voltage and lightning impulse voltage are simulated and studied by Comsol software.The simulation results show that in the electric field of the cable terminal,when the curvature of the stress cone is 54 mm,the electric field of the stress cone surface decreases more smoothly,and the position of the maximum electric field strength on the stress cone surface moves from the root of the stress cone to the top of the stress cone.The maximum electric field strength modulus of the stress cone inside and in the enhanced insulation decreases,but the electric field strength modulus decreases.The varying stress cone curvature has little relationship with the electric field modulus in XLPE insulation.The electrical conductivity of insulating materials in HVDC cable terminals varies greatly with temperature and electric field strength.In the process of modeling,EPDM and silicone rubber are selected as reinforcing insulating materials.The electric field distribution of cable terminals under different temperature gradients is simulated and calculated.The simulation results show that there are mainly three electric field intensity sensitive points in the electric field of cable terminals.The stress cone root,the reinforced insulating end and the stress cone top.Ethylene propylene diene rubber and silicone rubber can homogenize the field strength distribution of DC cable terminals,the field strength in the enhanced insulation decreases obviously,and the high field strength concentrates in XLPE.If temperature difference or the field strength at cable terminals increases,ethylene propylene diene rubber has more advantages than silicone rubber from the point of view of field strength modulus.