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 of 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 circumstances. We could conclude that the reason of "fast quench" in AC-cables is a specific mechanism of electromagnetic development of quench.
