Research On Electric Field Distribution Characteristics Of 200kV DC Cable Accessories

DC transmission has the advantages of flexible transmission,low loss,large current carrying capacity,easy control,little impact on communication and ecological environment,long distance and smart grid interconnection,and has become one of the development trends of high voltage long distance transmission in the future.Cable accessories,as an important part of power cable system,have become the weak link in HVDC transmission line because of their complex structure and complicated electric field distribution.When the DC cable attachment operates in steady state,the field strength distribution in the insulation is inversely proportional to the conductivity of the material,and the electric field is locally concentrated due to the discontinuity of the conductivity characteristics at the interface of the double layer medium in the attachment.Studying the influence of the electrical conductivity of the insulating material and the spatial characteristics of the interface on the electric field distribution of the DC cable accessories can guide the design of the DC cable accessories.In this thesis,200 kV prefabricated DC cable connector and DC cable terminal are taken as the simulation model,the influence of the insulation conductance on the electric field distribution of the DC cable connector under steady state and transient voltage is calculated by COMSOL Multiphysics software.At the same time,according to the experimental data,SPAW package to simulate the shape of the space charge accumulation on the interface of the medium in the terminal of the DC cable and calculate the influence of the different forms of the space charge accumulation in the interface space and thedifferent positions of the charge concentration on the terminal field distribution of the cable terminal.The results show that with the increase of voltage polarity reversal time,the field strength of XLPE inner field,the end of high voltage shielding tube and stress cone root tend to decrease,and the effective control measures are taken to reduce the conductance of insulating material activation energy can improve the non-linear correlation coefficient of insulation conductivity at the same time can improve the distribution of electric field inside the accessory;the space charge amount at the interface of cross-linked polyethylene and non-linear silicone rubber in DC cable terminal and its distribution in both sides of insulation HVDC cable The distribution of electric field of the terminal,the interface space charge in the insulating layer on both sides of the interface,the greater the radial concentration,the greater the value of field strength XLPE terminal high voltage DC cable,that is the more serious the electric field distortion;cross-linked polyethylene and non-linear silicone rubber When the distance between the central peak of the space charge accumulation on the interface and the root of stress cone gradually increases,the maximum field strength in the terminal decreases exponentially,and the maximum field strength in the reinforced insulation slowly increases to a stable value.