A Combined Circuit-FEM Model of HTS Power Cables for their Analysis During Critical Transients

The paper discusses the development and application of circuit models for superconducting DC power cables to investigate their interaction with the power system. These models, created as part of the SCARLET project, simulate the behaviour of different cable components (e.g., HTS layers, shield, cryopipes) during power system transients like energization and faults. By integrating these models with power system simulators, accurate current profiles of the cable components are obtained. Additionally, the paper introduces a combined circuit and 2D finite element method (FEM) model to study the electro-thermal behaviour of the cable. The circuit model is developed to account for all the relevant factors like the E-J power-law characteristic, the magnetic field's influence on the superconductor and heat generation. Then the FEM model provides the detailed electro-thermal behaviour of the cable components considering the current profiles obtained from the circuit model as input, enabling efficient and focused simulation of localized effects without the computational complexity of fully coupled simulations. Using this combined model, the performance of a reference HTS cable under a pole-to-pole fault is analysed. Results show a limited temperature increase during transients, including both energization and fault scenarios, with peaks of only fractions of a Kelvin occurring immediately after the pole-to-pole fault. The FEM model further provides detailed temperature maps, illustrating the corresponding temperature distribution throughout the cable components, proving the save operation on post restoration.