Electric Field Analysis And Experimental Research On 10kV Cold-shrink Cable Accessories

Cold-shrink cable accessories play an important role in the connection and transition of cable lines,and are an integral part to ensure the reliable operation of power systems.Due to the complicated internal structure and different materials of cable joints,it is easy to produce electric field distortion,which has become a weak link of cable transmission lines and a typical part of operation failure.To improve the operational reliability of the cable joint system,on the one hand,it is necessary to ensure that the on-site manufacturing process of the cable joint system is standardized,and the environmental conditions(such as humidity)at the manufacturing site should meet the requirements.More importantly,the cable accessories should be optimized to improve the design quality of the product.In order to study the influence of the defect of the intermediate joint of the 10 kV cold-shrink cable on the electric field distribution and explore the electric field distribution of the defect at different positions.Firstly,a finite element simulation model for the defects of 6 types of cable intermediate joints is established.Then the model is used to analyze the electric field distribution law of the defect at different positions of the intermediate joint.Finally,six defect intermediate joints were made according to the analysis results,and partial discharge and withstand voltage tests were carried out on the samples.The results show that the main insulation is scratched,the main insulation has copper particles,and the main insulation has a semi-conductive tip located below the end of the stress cone,the electric field is greatly distorted.However,as the distance between the defect and the outer semi-conductive layer is increasing,the influence on the electric field is gradually decreasing.When the connecting tube is misused with insulating tape,the electric field distortion at the tape is obvious and the degree of distortion is inversely proportional to the thickness h of the insulation.When the cable attachment is offset,the electric field distortion intensity increases as the distance of the offset increases.When the burr is on the tip of the connecting pipe,there is a large electric field concentration at the burr.Partial discharge and withstand voltage tests prove that the partial discharge detection system can effectively detect most cable joint defects,but there are still some limitations on the detection of the tip burrs of the connection tube.In order to meet the design requirements of modern products,this paper takes the medium-voltage cold-shrinkable cable intermediate joint as a model,and optimizes its structural parameters according to the electric field distribution law.The finite element simulation model of the cable intermediate joint is established firstly,and then the structural parameters matching of the intermediate joint is deeply analyzed by using the model.Finally,a 10 kV cold-shrink cable intermediate joint is made according to the analysis results.The simulation and test results show that: By optimizing the structural parameters of stress cone and shielding tube,when the axial length,curvature radius and thickness of stress cone are 65 mm,25 mm and 2.5 mm respectively,the length and shape of shielding tube are 170 mm and 90 degrees respectively,the distance between stress cone and shielding tube is 60 mm,and the length of intermediate joint body is 420 mm.The maximum field strength and tangential field strength of the sample are less than 30 kV/cm(air breakdown field strength)and the electric field distribution on the interface is more uniform.The design requirements can be met by partial discharge and voltage withstand test,which provides a theoretical basis for the reasonable design of 10 kV cold shrinkage intermediate joint.