Influence Of Nonlinear Barrier On Electric Field Distribution In HVDC Cable

HVDC transmission has become a research hotspot in the field of electrical engineering.Electric field distribution of cable insulation is the main factor to long-term and reliable operation of HVDC cable.More uniform the distribution of electric field is,higher the reliability of the insulating structure will be.The nonlinear insulation material has unique electrical conductivity.Its conductivity and relative permittivity change with the variation of field strength.It not only has the ability of homogenizing the electric field distribution by itself,but also have obvious inhibition effect on electrical trees growth and the formation of space charge.Therefore,nonlinear material is tried to use as barrier layer and putted between shield and insulation.It is hoped that the structure can make the electric field distribution of HVDC cable insulation more uniform,reduce the thickness of insulation layer and reduce the technical difficulty of developing pure insulating materials.According to the actual situation,And the simulation model is established by the software of COMSOL Multiphysics.At different temperature gap,it is studied that the influence of barrier layer structure to the electric field distribution and space charge of HVDC cable insulation.And the analysis of the interface charge between the barrier layer and generating insulation.On this basis,we continue to study the influence of the thickness of the barrier layer and the material properties in the non-linear barrier layer on the distribution of the electric field.The simulation results show that compared with the non-barrier cable,the HVDC cable with the barrier layer structure has the ability to homogenizing the electric field.At different temperature gap,the steady and transient electric field strength maximums of the cable insulation without barrier layer are both higher than the maximum value of HVDC cable with barrier layer.And the space chargein HVDC cable insulation with nonlinear barrier layer structure are less than the non-barrier layer structure.As the barrier layer thickness increases,the space charge in the insulation and the maximum field strength decreases,but the interface charge increases.In the nonlinear barrier layer,with the change of nanomaterial properties,the activation energy and the electric field dependence coefficient of conductivity will also change.If the numerical value is too high or too low,it will have a negative effect on the electric field distribution of barrier layer.According to the simulation results,the electric field distribution of cable insulation can be optimized by barrier layer.However,it also causes the accumulation of interfacial charge.So when developing the HVDC cables with nonlinear barrier layer,the interface charge accumulation and electric field distribution should be considered for the selection of barrier layer thickness,so as to improve the cable insulation performance.