A Resistance Model of Fault Current Limiting Coils Under DC Impact

The short-circuit fault current on the dc side affects the operation safety of the multiterminal flexible HVdc (MTDC) transmission system seriously. The resistance-type superconducting fault current limiter (RSFCL) has received extensive attention in limiting the dc impact current because it has a fast response speed and zero impedance at a steady state. At present, there are so many works on the simulations of RSFCLs but the error is relatively larger, which affects the design accuracy of RSFCLs. In this article, the characteristics of dc fault current limiters are studied. The resistance and other parameters of yttrium barium copper oxide (YBCO) samples under the dc impact are measured. The equivalent heat capacity and the equivalent heat dissipation of YBCO tapes are defined and calculated to analyze the heat transfer process of YBCO tapes under the dc impact. A modeling method based on the equivalent heat parameters is obtained. In addition, the thermal balance point during the dc impact is defined by that thermal power production and heat loss of the YBCO tape are equal to identify the credible boundary of the resistance curve. Finally, the correctness of the proposed method is verified by the experimental results of fault current limiter coils and compared with the R-Q fit model. This research aids in the simulation analysis and optimization design of dc RSFCLs.