Electrical fault analysis of NET poloidal coils

A mathematical model and a corresponding computer code which allows the analysis of the behavior of a system of circular mutually coupled superconducting coils are described. The analysis can be performed during normal operation and during fault conditions. The faults considered are short circuits between windings or shorts to ground in one or more coils. The electrical part of the model is obtained by means of circuit theory applied to the network formed by the coils and the power supplies. The network structure changes for each fault condition because two or more subcoils must be considered in order to simulate one faulted coil. The model takes the occurrence of fast discharges and/or quenches into account. The thermal part of the model connects the temperature to the quench resistances and to the currents flowing into the coils. The evaluation of quench resistances is based on an adiabatic model. The model is applied to the poloidal system of the Next European Torus (NET) tokamak for the evaluation of the currents when a fault occurs