Research On Current Carrying Capacity And Ac Loss Characteristics Of Different Arrangement And Initial Phase Of Current Of Hts Cable

The emergence of the second generation of high-temperature superconducting materials has promoted the further development of superconducting technology.The superconducting current limiter has many positive effects on the operation of the power grid,but how to increase the critical current of the superconducting current limiter and reduce the AC loss is still a problem that needs to be solved in the current research work.In the resistive superconducting current limiter,the wire cake and the strip are stacked on each other.The impact of different current directions and different arrangements on the critical current and AC loss will directly affect the performance of the resistive superconducting current limiter,which in turn affects the stable operation of the power grid.This article uses experiment and simulation methods to compare the first and second generation high-temperature superconducting tapes and TSTC(Twisted Stacked-Tape Cable)and QIS(Quasi-Isotropic Super-cable)cables and their combined structures.The current-carrying performance and AC loss under the arrangement and flow mode are studied.And using experimental methods,the difference between the current-carrying performance and AC loss of the first-generation and second-generation high-temperature superconducting cables under tension and lateral pressure has been studied.The specific work content is as follows:Using experimental methods,it is found that in different arrangements and current flow modes,the critical current of the current in the same direction is smaller than that of the reverse direction when stacked;in parallel,the critical current of the current in the same direction is greater than the reverse direction,and the difference is greater when stacked.Between the two strips,the magnetic fields generated by currents in the same direction are superimposed on each other,and the magnetic fields generated by the reverse current flow cancel each other out.When stacked,the main direction of the magnetic field is parallel to the strip,so the critical current of the current in the same direction is smaller than the reverse direction;when parallel,the main direction of the magnetic field is perpendicular to the strip,so the critical current of the same direction current is greater than the reverse.The variation range of Bi2223 strip is larger than that of YBCO strip,because the critical current anisotropy of Bi2223 is not as good as that of YBCO.With the increase of the current frequency,the single-cycle AC loss of YBCO and Bi2223 has a slight decrease.In the case of the same current,the AC loss in the same direction of the stack is greater than the AC loss in the reverse direction of the stack;the AC loss in the same direction is less than the AC loss in the reverse direction of the stack.Under the same arrangement,the difference in AC loss between YBCO co-current and reverse current is greater than that of Bi2223.This is because YBCO strips are thinner than Bi2223,and the effects of magnetic field superposition and cancellation are more obvious.Under the action of mechanics,due to the structure and substrate,the critical current,n value and AC loss of Bi2223 strips are not as good as YBCO strips under the pressure and tension of the receiving side.The method of finite element analysis found that the maximum critical current of a single TSTC is 2765.92 A and the minimum is 2238.78 A under the four current flow modes,and the ratio of the two is 1.24 times;the single QIS is critical under the three current flow modes.The maximum current is 2704.44 A and the minimum is 2279.47 A.The ratio of the two is 1.19 times.In the TSTC composite cable,the maximum critical current is 5633.2A,the minimum is 4223.4A,and the ratio of the two is 1.33 times;in the QIS composite cable,the critical current is the maximum of 5429.6A and the minimum is 4467.3A,and the ratio of the two is 1.22 Times.When a 400 A amplitude AC is applied to each small conductor,the maximum transmission loss of the TSTC combined cable is 0.55236J/Cycle/m,the minimum transmission loss is 0.09749J/Cycle/m,and the ratio of the two is 5.67 times;In the QIS composite cable,the maximum transmission loss is 0.48597J/Cycle/m,and the minimum transmission loss is 0.10135J/Cycle/m.The ratio of the two is 4.79 times.It can be seen that the critical current and AC loss of a single QIS and its combined cables are not as good as those of TSTC and its combined cables,but the difference between the maximum value and the minimum value is smaller than that of TSTC.