Conceptual design of air-core superconducting transformer for 500 kV cable transmission system

The air-core superconducting transformer, which has a large magnetising current, has been proposed as a possible type of future power transformer having a function as a shunt reactor. In this paper, a basic design procedure for the air-core superconducting transformer is presented. By using this procedure, a 500/√3 kV-66/√3 kV-300 MVA single-phase air-core transformer which includes the function of a 100 MVA shunt reactor is designed. The size, weight, loss and capacity of this transformer are compared with those of a conventional transformer, and the performance of the designed air-core transformer in the model cable transmission system is analysed. From the results of these investigations, it is confirmed that the air-core superconducting transformer can function as a shunt reactor in addition to its principal function as a power transformer, and the merits of the air-core superconducting transformer are clarified