Insulation test of reciprocal and concentric winding arrangement for a HTS transformer

In Korea, the Hyosung Industrial, Korea Polytechnic University and Gyeongsang National University are developing a power distribution and transmission class HTS transformer that is one of the 21st century superconducting frontier projects. For the development, it is necessary to establish the dielectric technology at cryogenic temperature such as insulating design, cooling system, manufacture, compact, and so on. Also, verification of insulating stability is an important dielectric technology. Therefore, we prepared two models, one is concentric arrangement, the other is reciprocal arrangement, from Kapton insulated Cu tape for a small simulated HTS transformer and measured their insulation characteristics such as PD, ac (50 kV, 1 min) and impulse (154 kV, 1.2×50 μs) withstand test. Before manufacture of each model, we have analyzed insulation composition and investigated electrical characteristics such as breakdown of LN₂, polymer and surface flashover on FRP in LN₂. We are going to compare with measured each value and apply the value to most suitable insulating design of the HTS transformer.