Simulation Of Transient Electric Field In Insulation Structure With Non-linear Dielectrics

Non-linear dielectrics are the insulating dielectrics whose electric conductivity or/and relative dielectric constant change with electric field, have been extensively applied in complex insulation structure due to the functions of grading the electric field. In this paper, the coaxial electrodes structure filled with non-linear conductivity or/and non-linear relative dielectric constant dielectrics is taken as main research object, and transient electric field distribution of nonlinear insulating dielectrics is simulated under the step voltage, AC and impulse voltage.The transient 2D solver in the electric field simulation software named ElecNet is adopted to simulate the transient electric field in the coaxial insulation structure with the non-linear insulating dielectrics in this paper. The result indicates that the non-linear conductivity dielectrics have the functions of grading the electric field at the steady state and lead to the increment of insulating utilization coefficient, under the step voltage. The nature of the nonlinear conductivity dielectrics in grading the electric field and enhancing insulating utilization coefficient is space charge effect. The non-linear relative dielectric constant dielectrics have the functions of grading the electric field at the initial state of the step voltage, whose insulating utilization coefficient is lower. The dielectrics with non-linear conductivity and relative dielectric constant have the functions of grading the electric field at the whole time, which have the best degree of electric field improvement.Under AC and impulse voltage, according to the theory of space charge limited field, the capability of the non-linear dielectrics in grading field is determined by the dominator of resistive current and capacitive current. When resistive current is larger than capacitive current, the non-linear conductivity dielectrics have the function of grading the electric field, vice versa. Electric field distribution of cable termination with stress cone structure is simulated in this paper. Electric field distribution of silicone rubber insulation with linear insulating dielectrics is compared with silica insulation with nonlinear insulating dielectrics. The result indicates the application of non-linear insulating dielectrics reduce total electric field outside stress cone surface as well as the biggest total electric field of stress cone end tail, has affected slightly axial electric field of cable insulation and stress cone interface as well as the silica insulation and air interface.