Quench development in superconducting cable having insulated strands with high resistive matrix. I. Experiment

The process of quench development in two- and six-strand cables was investigated in detail. Different types of quenches were found. The increase of the starting current level led to a change in the nature of the quench, from current redistribution, to a quench in all strands, to multi-quench with acceleration of the process from step to step, and to fast quench. Strand currents never achieved the critical current value under DC conditions. It is concluded that the cause of fast quench in AC cables is a specific mechanism of the electromagnetic development of quench. It is caused by a rapid redistribution of currents between the strands, which leads to a multi-quench process with acceleration of the normal zone propagation after each quench of the strand. The cause of the fast redistribution is the high inductive coupling coefficient between strands