Abstract For the development of electrical insulation design of a HTS transformer with Z continuous winding, we have discussed insulation composition and investigated breakdown characteristics such as breakdown of LN 2 , polymer and surface flashover on FRP and breakdown-surface combination in LN 2 . Also we have designed and manufactured a bobbin that has spiral slot for the Z continuous winding. A Z continuous winding mini-model from Kapton film insulated Cu tape for simulated 22.9 kV class HTS transformer has been constructed using 0.1% breakdown strength obtained by Weibull distribution. The winding model was measured with respect to its insulation characteristics such as ac (50 kV, 1 min) and impulse (154 kV, 1.2 × 50 μs full wave, 3 times) withstand test and its excellent performance was confirmed.