Design requirements of a high temperature superconducting transformer

Abstract

We studied the technical design targets of high temperature superconducting (HTS) large capacity transformers through the design of 3-phase 66 kV–100 MVA transformers, expecting further performance progress of HTS tapes. It is required for large capacity transformers installed in a power system to have enough percent impedance %IX in order to limit a fault current in the power system at the time of a short circuit accident. It is not easy at the present technical level for HTS transformers wound with Bi-2223/Ag tapes to secure enough percent impedance due to low air gap fields. The design targets are a percent impedance of 7.5%, an air gap flux density of 0.3 T, tape current density of about 40 A/mm 2, winding strain of about 0.5% and AC losses of about 0.3 W/km A.