I. Introduction
The prediction of the behavior of a superconducting coil during a transition from the superconducting state to the normal state is important because this phenomenon can lead to the destruction of the device. Historically the Wilson's QUENCH [1] program was the first published code allowing quench simulation of a superconducting coil on a computer. Despite its simplicity, this approach gives globally correct results [3] [4] [5]. Another approach is to treat the coil as a anisotropic solid and solve the nonlinear heat equation governing the quench process with methods like the finite-element method. But due to the existence of very strong temperature gradients such simulation required a large computing effort [2] (they use a Cray). We propose here an intermediate method which is more powerful than the Wilson's method but which is still very fast compared with finite-element method oriented approaches. This method can be very interesting during the design process where a lots of configurations have to be tested with a moderate accuracy. Definition of and using the level-set of a function . Evolution of : merging of two normal zones.