Research On Key Technologies Of Low Voltage Self-shielding DC High Temperature Superconducting Cable With Large Current Capacity

Compared with the high temperature superconducting(HTS)AC cable,HTS DC cable has large current capacity,low AC loss and higher controllability.In order to reduce the influence of magnetic field generated by itself on the critical current,a new configuration of DC HTS cable,self-shielding DC HTS cable,is researched.With analysis on the current status and future development tendency of HTS DC cable at home and abroad,through theory and experimental method,the critical current anisotropy and current transfer length is studied first.Then,the design method of cable conductor,termination influence and connect method et al.are studied.Through the analysis results,a self-shielding DC HTS cable is fabricated and the experiment is done to verify the feasibility of the cable.Finally,the cryogenic characteristic of long distance HTS DC cable is analyzed which can provide reference to the engineering application of self-shielding HTS DC cable.Through the self-consistent model,the critical current anisotropy under external magnetic field of 2G HTS tape is studied using the simulation method.After the comparison between experimental and simulation results,the empirical formula of critical current anisotropy under external magnetic field is got which can provide reference for the simulation of HTS cable.The design principle of cable former,layer number,number of tapes in each layer,total tapes,winding angles in each layer and insulation layer in self-shielding DC HTS cable is introduced.Then the structure advantages of self-shielding DC HTS cable is analyzed.The influence of termination is researched.A method to calculate the magnetic field influence generated by the termination on the cable critical current is proposed,the force among the current leads in the termination is also analyzed.According to the influence of termination and connection difficulty,two methods of connection between current lead and HTS tapes in the termination are proposed.The current transfer length of 2G HTS tape is also studied,through the experimental results,the best soldering length of 2G HTS tape is got which is very important for the connection of current lead in the termination.Through the simulation method,the magnetic field of each layer,critical current and AC losses of conventional structure cable and self-shielding cable are analyzed.Based on the analysis results above,a self-shielding DC HTS cable model is fabricated.The experimental test is done under liquid nitrogen temperature,including connect resistance,critical current and short circuit current test.The temperature and critical current distribution along length of HTS DC cable is studied,the exterior loss,flow rate,heat exchange and wall roughness influence on the longest cryogenic length are also analyzed.