68 / 2021-06-04 09:16:25

Preliminary Electrostatic Analysis and Insulation Design of High Voltage Transmission Line towards the CRAFT NNBI Test Platform

In order to satisfy the requirements of China Fusion Engineering Test Reactor (CFETR) for neutral beam injector system, a Negative-ion Based Neutral Beam Injector system (NNBI) test platform towards the Comprehensive Research Facility for Fusion Technology (CRAFT) will be established by Institute of Plasma Physics Chinese Academy of Sciences (ASIPP). The High Voltage Transmission Line (HVTL), which adopts SF6 gas insulation technology, plays an important role in the NNBI system, connecting the ion source and the power supply system. The HVTL is mainly composed of -200 kV intermediate voltage conductor, -400 kV high voltage conductor, grounding shell, post insulators (including metal inserts) and particle trap. Therefore, it is necessary to analyse and design the insulation structure of the HVTL.

Aiming at the insulation problem of the HVTL, this paper studies the insulation structure of the HVTL from the following three aspects through finite element analysis: the layout structure of the HVTL conductor, the structure of post insulators and the metal inserts, and the basic structure of particle trap. Firstly, the insulation design requirements of the HVTL are put forward, and the dimensions of the conductors and the grounding shell of the HVTL are determined according to the design theory of the coaxial transmission line and design requirements. And the effects of different positions of the high voltage conductor and the intermediate voltage conductor and different diameter of the grounding shell on the electric field in the HVTL and equivalent distributed capacitance of the HVTL are analysed, and the layout of the conductors and the grounding shell of the HVTL is determined according to the insulation design requirements. Then, the influence of different structural parameters of insulators and metal inserts on the electric field is analysed, and according to the design requirements of the insulation of the insulator, the preliminary main design structural parameters of the post insulator (including metal inserts) are determined. At the same time, the influence of different material parameters of insulators on the charge accumulation characteristics of gas-solid interface is analysed, and according to the design requirements of surface charge density, the material properties of insulators are determined. Finally, according to the working principle of the particle trap, the influence of the particle trap on the average electric field intensity at the bottom of the trap under different width and depth of the trap slot is analysed. And according to the design requirements, the basic structure parameters of the particle trap are determined. These simulation results and the determination of structural parameters of the HVTL provide a theoretical basis for the engineering design of the HVTL towards the CRAFT NNBI test platform.