Protection of superconducting transformers from the quench caused by excess fault current was studied theoretically with the aid of a simple equivalent circuit model which was composed of leakage inductance and resistances of the conductor. We distinguished the resistance in the flux-flow state from that in the normal state, and basic parameters of the transformer, such as sizes, leakage inductance and conductor length were described as functions of one-turn voltage. The quench process after the short-circuit was numerically analyzed by this circuit equation with the aid of the heat-balance equation. It was shown that the maximum temperature rise of the conductor until interruption of the power line increases monotonically with the one-turn voltage, but has a minimum around several percent of the copper ratio in the conductor. To suppress the temperature rise, therefore the one-turn voltage should be limited to smaller values than that in the conventional transformers even if the copper ratio is optimized for the rated capacity and voltage.
All Science Journal Classification (ASJC) codes
- Electronic, Optical and Magnetic Materials
- Electrical and Electronic Engineering