Conceptual design of 100 MVA high temperature superconducting auto-transformers

This paper describes the conceptual design of 100 MVA high temperature superconducting (HTS) autotransformers as well as coreless ones having the rating of three-phase, 50 Hz, and 132 kV/66 kV. Each one is compared with conventional oil-immersed autotransformers. The HTS autotransformers with core will provide a percent impedance of 11.7% close to the conventional one and require an air gap field of 0.33 T, while the coreless HTS autotransformers require 25.8% and 0.7 T respectively. HTS autotransformers with a core have a 22% smaller window size and 0.3% higher efficiency than conventional ones. The coreless HTS autotransformers need HTS tapes about two times the length required for the HTS autotransformer with a core.