Calculation of transient electrical behaviour of ITER PF coils

The verification of the high voltage design of the magnet system is an important issue for a reliable operation of the ITER machine. Transient electrical excitations occur on the PF coils for example during the normal operation, in case of a fast discharge or if a failure appears in the components of the electrical circuit. For proper insulation co-ordination it is important to determinate the transient electrical voltage distribution within the coils. The maximum calculated voltages of all relevant cases will yield a necessary basis for testing parameters for different kinds of insulation, e.g. turn, layer or ground insulation. With Finite Element Method (FEM) models calculated values for lumped elements were used to build the network models for PF 3 and PF 6 coils. First the resonance frequencies of the PF 3 and PF 6 coils were calculated, which give the first benchmark for the calculation of transient electrical behaviour of these coils. Further the influence of instrumentation cables on the resonance frequency of the coils was calculated, which causes a decrease of resonance frequencies to lower values. The methods of calculations and results for resonance frequencies with and without two types of instrumentation cables are presented.