Abstract
In this paper, through AC and DC overcurrent tests on second generation high temperature superconducting tape (2G HTS tape), we respectively summarize the typical types of quenching resistance and corresponding quenching degree, in which there are three types under AC overcurrent and two types under DC overcurrent. According to experimental results, a rule was found that, when 2G HTS tape quenches to normal state, the relationship between quenching resistance and joule heat generated from 2G HTS tape presents a fixed trend line, and the influence of liquid nitrogen can be ignored. Then, the characteristics and rules of quenching resistance found in experiments are well explained and confirmed by a detailed 3D finite element model of 2G HTS tape including electromagnetic field and thermal field. Finally, based on above works, our group proposes a new equivalent method to estimate the quenching resistance, where the results of AC and DC overcurrent experiments can be equivalent to each other within a certain range. Compared with FEM, the method has the following advantages: (i) The method is simple and easy to implement. (ii) This method combines precision and computational efficiency. (iii) With superconducting tape quenching to normal state, this method presents a good consistency with experimental results.
Highlights
With the discovery of the cuprate-based high temperature superconductors, first generation high temperature superconducting (1G HTS) tapes represented by BSCCO (Bismuth Strontium CalciumCopper Oxide) Ag-sheathed conductors and second-generation high temperature superconducting (2G HTS) tapes represented by YBCO (Yttrium Barium Copper Oxide) coated conductors have appeared successively [1,2]
When the superconducting tape enters normal state, it is approximately in an adiabatic environment, and quenching resistance will vary with the accumulated joule heat along a fixed R-Q curve, which is consistent under alternating current (AC) and direct current (DC) overcurrent
When superconducting tape starts to quench, the accumulated joule heat Q in each time step is calculated by discrete calculation, whose corresponding quenching resistance R can be obtained by interpolation calculation based on R-Q curve
Summary
With the discovery of the cuprate-based high temperature superconductors, first generation high temperature superconducting (1G HTS) tapes represented by BSCCO A new estimation method is proposed, which can accurately reflect and estimate the quenching resistance within a certain range, whose feasibility and availability was verified by comparing with experimental results It provides theoretical basis and experimental support for AC equivalent test method before a large-scale DC R-SFCL connected to DC power grid. The 2G HTS tape is 12 mm wide with a two-core configuration, including two typical structures of YBCO tape with copper stabilizer on both side, which are stacked back-to-back and encapsulated with stainless steel layer, as shown in Figure 1a,b (buffer layer is omitted) This structure can increase self-field critical current, which is suitable for power systems with high current. (b) sectional view; and (c) the sample prepared for experiment
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