In a previous study, we developed a 66/6.9 kV-2 MVA REBa2Cu3Oy (REBCO) superconducting transformer with a current-limiting function that was cooled with subcooled liquid nitrogen at 65 K. By considering the flux-flow state, it is possible to quantitatively explain the behavior of REBCO superconducting transformers and cables subjected to a sudden short circuit. Our goal was to demonstrate that limiting an excess fault current to triple the rated current after 0.2 s (while maintaining a superconducting state) was possible with the cooperation of superconducting transformers and cables. For that purpose, a numerical analysis was performed by coupling thermal equations and circuit equations. Consequently, the numerical analysis demonstrated that limiting the excess fault current to triple the rated current after 0.2 s can be achieved by adjusting the thickness of the stabilizing copper layer of REBCO superconducting tapes and the length and critical current, Ic, of the superconducting cable. Through these simulations, the balance of Ic and thickness of copper layers was shown to be important in limiting overcurrent and normal transition rates of the superconducting winding of the transformer and cable.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Electrical and Electronic Engineering