Research Of Design And Fabrication On ITER HV Cable Splicing Device

Splicing devices(SD)are used in the ITER machine to connect high voltage(HV)individual wires with HV cables to provide insulation,structure and signal shield protection.The SDs work under high vacuum,cryogenic temperature,strong electromagnetic and radiation conditions,therefore,materials and structural design were strictly required for the HV splicing devices.Similar structures used for power cables can hardly fulfill the requirement of materials used in fusion device,so it is necessary to develop a new type of splicing device used in the ITER machine.Material selection,electrical and mechanical performance analysis,assembly process and performance tests of high voltage splicing device are performed in this dissertation.Researches on structure materials were carried out under the working conditions of HV splicing device.Firstly,toughening methods of epoxy resin system were presented to improve its cryogenic properties.Secondly,the bonding strength between glass and epoxy resin was improved by using silane coupling agent and corona treating method.Thirdly,the dielectric property of epoxy resin system was adjusted by adding nano alumina particles.At last,the coefficient of linear expansion and out-gassing rate of glass fiber reinforced epoxy resin composite tests were performed to prove that the results can fulfill the allowable value.A new structure of HV SD with electromagnetic shielding was designed according the technical requirements of HV splicing device from ITER organization.Electrical field analysis,stress analysis during cooling-down process was performed to prove the design is reliable.The analysis results indicate that the insulation is dangerous under helium leak condition,so helium tightness of high voltage splicing device is necessary.For 30 kV splicing device,high voltage electrode with helium tightness and semiconducting layer are designed to reduce the electrical strength at the interface of two materials.Moreover,to reveal the influence of defects of the electrical performance of HV splicing device,the existing defect types of glass fiber reinforced epoxy resin composite were discussed.The simulating model with defects was established and the electrical field analysis was performed,the results indicate that defect can lead to electrical field multiplied at the interface of two materials,so it is necessary to reduce the defects of high voltage splicing device so as to ensure the safety of insulation.According to the technical requirements of site installation of high voltage splicing device from ITER organization,investigation on VR assembly of the high voltage splicing device was performed by computer aided design technology,the practicability of modular structure design was verified,as a result,the assembly sequence of from left to right and from inside to outside is determined.For the developed high voltage splicing device,routine test including electrical performance and thermal cycle tests were performed to check the cryogenic and electrical properties of HV SDs,the results indicate the insulating performance is qualified after 50 times of thermal cycles.In addition,the results of Paschen discharge and partial discharge indicate the helium tightness performance and defect control of HV splicing device are satisfactory,and the developed prototype HV splicing device can meet the technical requirements of ITER organization.