INVESTIGATION ON TRANSIENT OVERVOLTAGES IN A LARGE WINDING FOR A FUSION DEVICE DURING INSULATION TESTS

In this paper an application of a method for the analysis of internal transient voltages in large windings is presented. The method, develop ed to study the voltage distribution inside simple coils, is based on the representation of the coil as a lumped circuit. It has been applie d to the Poloidal Field Block I1 of the RFX machine, which is composed of 8 independent coils with 96 turns in total. Due to the geometrical complexity of the Block, groups of turns have been represented with g lobal equivalent parameters, in order to reduce the model size and the computation time. A number of simulations have been performed, whose results are in good agreement with the measurements taken during tests , so that this model has been used for the interpretation of a breakdo wn occurred to Block I1 during acceptance tests.