Analysis of Impact of RSFCLs on Fault Detection Schemes for DC Grid

Resistive type superconducting fault current limiters (RSFCLs) provide effective protection for a DC grid against a short-circuit fault; however, the installation of such fault current limiters also alters the measured signal, which will then affect the fault detection schemes. Existing literature does not show any thorough consideration of this critical issues. In this paper, after establishing the equivalent quench model of an RSFCL based on the characteristics of the superconducting YBCO tape, a theoretical analysis of the influence of the RSFCLs on the measured time-domain signal is carried out. The analysis yields mathematical expressions for the change of the measurement signals with and without the addition of RSFCLs. The appropriate value of the RSFCL resistance is selected according to the PSCAD/EMTDC simulation results. While verifying the results of the theoretical analysis, it is found that adding the RSFCL could increase the fault detection time by more than 40%. The paper fills an important gap in the existing knowledge about the influence of RSFCL on fault detection in DC systems, and also provides a base line for the design of the RSFCLs and fault detection method for DC systems.