Study of Electromagnetic and Thermal Transients in a High-temperature Superconducting Transformer during a Short Circuit

Today, high-temperature superconducting (HTS) current limiters and transformers allow to limit the surge short circuit current during failure without negatively affecting on the power grid complex at the normal operation mode. However, the transition of a superconductor to a resistive state at the moment of current limitation can cause significant heat generation, which can destroy the transformer windings. The research goal is to provide optimal technical characteristics of the HTS transformer to achieve effective short circuit current limitation and prevent thermal breakdown of its windings. To achieve this goal, a mathematical model of a HTS transformer was developed. The presented method considers the material type and geometry of the superconducting tape, the critical parameters of the superconductor (current and temperature), the parameters of the cryogenic liquid, dependence of the resistance and heat capacity of the HTS tape layers on temperature. The simulation model was created in the Matlab/Simulink software. The most important result is the possibility of obtaining optimal electrical and thermal parameters of the HTS transformer windings during the short circuit current limitation, as well as ensuring the thermal stability of the superconducting tape at the quench moment. The obtained results are significant in the design and operation of HTS transformers. For efficient and safe operation in the current-limiting mode, it is necessary to take into account heat generation on the transformer windings. It is important for the superconductor returning to the superconducting state without causing significant overheating of the windings.