Electromagnetic Calculation of a 35 kV/3.5 MVA Single-Phase HTS Controllable Reactor With Field-Circuit Coupled-FEM

A controllable reactor is able to compensate a flexible reactive power in a long-distance and an ultrahigh-voltage system. A high-temperature superconductivity controllable reactor (HTS-CR) is a potential equipment in the power system. A method to accomplish the electromagnetic calculation of the HTS-CR is proposed, wherein the field-circuit coupled finite-element method (FCC-FEM) is introduced. Test results of the steady-state current of all the windings of an HTS-CR prototype is compared with the calculation results, which proves the reliability of FCC-FEM. Based on FCC-FEM, the accuracy of the four-probe method, which is used to measure the dc critical current of HTS winding with the criterion 10 -6 V/cm, is studied. Contrary to the four-probe method, a new method based on FCC-FEM, which has better accuracy, is designed to calculate critical current. With FCC-FEM, distributions of the current in the parallel-connected HTS tapes and the ac critical current of the HTS windings for a 35 kV/3.5 MVA single-phase HTS-CR are presented.