Protection of superconducting AC windings

Protection schemes for superconducting AC windings are proposed which are applicable when the conductor is made up of several wires. Attention is first given to active protection, which involves ultrarapid quench detection. It is based on the measurement of the current passing through the central resistive wire and/or of unbalanced currents in the different superconducting wires. About 20 ms after detection, a fast circuit breaker switches off the current. Also considered is a complementary passive protection, which is provided by the resistance developing during normal phase propagation. This behavior naturally induces a certain amount of current reduction. Experimental results show how this effect can be magnified through an adequate definition of the superconducting and resistive wires assembled in the conductor