Development and qualification of ITER current lead electrical insulation

•The ITER current lead insulation consist of interleaved pre-preg and polyimide tapes.•The acceptance high voltage test for current lead includes DC, Paschen and PD test.•ASIPP has completed the insulation qualification of ITER current lead. The ITER high temperature superconducting current lead is a critical component for the magnet system, which has the benefit of reduction in the heat load of the cryogenic system compare with the conventional lead. The current lead is located in the coil terminal box and dry box at the end of the ITER feeder system. As a warm to cold transition section, the current leads feed the huge current from the power supply system into the coils. At the outer surface of the current lead, one layer of a composite insulation is applied to isolate the high voltage potential of the current lead to the ground potential of the environment. The main body of the current lead is that of a long cylinder, but at the cold termination and the cooling inlet, the local geometry is much more irregular. So the insulation wrapping and curing technology of the current lead had to be developed to acquire its uniform mechanical and electrical performance. Now, the multi-stage autoclave curing technology has been qualified in ASIPP and the series ITER current leads are being manufactured based on the qualified procedure. In this paper, the latest insulation progresses for the ITER current lead are introduced, the high voltage testing results as part of the formal qualification are presented and discussed.