Conceptual Design of a 25.8 kV, 2.0 kA Resistive SFCL for Power System Interconnection

Abstract

This article presents conceptual design of a 25.8 kV / 2.0 kA resistive superconducting fault current limiter (R-SFCL). The local utility, Korea Electric Power Corporation, has a plan to introduce 154/22.9 kV mini-energy centers (mini-ECs) in urban, a kind of small-scale substations, in 2023, as a pilot project. And the R-SFCLs are expected to install at bus section and bus coupling locations between mini-ECs in order to operate stable loop system on 22.9 kV. The utility demanded the compact R-SFCLs which consist of two cubicle switchboards, each of which is 2,400 mm in width 2,800 mm in depth 2,800 mm in height, due to space constraints of the mini-ECs. To meet the requirements, we applied a fast switch (FS) which disconnects the circuit in half cycle after a fault and a modular-type current limiting resistor (CLR) instead of reactor type. The first cubicle switchboard is a superconducting part, which includes high temperature superconducting (HTS) modules and a cryocooling system. And the other is a non-superconducting part, which includes FS, CLR, control units. The HTS module is a combination of multiple bifilar coils wound with HTS tapes supplied by SuNAM. The three-phase HTS modules are cooled by subcooled liquid nitrogen in a single cryostat, which has a sidewall cooling structure particularly useful when electrical insulation and compactness are required at the same time.