Longitudinal Insulation Design of Hybrid Toroidal Magnet for 10 MJ High-Temperature Superconducting Magnetic Energy Storage

A hybrid toroidal magnet using MgB textsubscript 2 and YBCO material is proposed for the 10 MJ high-temperature superconducting magnetic energy storage (HTS-SMES) system. However, the HTS-SMES magnet is susceptible to transient overvoltages caused by switching operations or lightning impulses, which pose a serious threat to longitudinal insulation. Accurate and efficient simulation of the voltage distribution characteristics of HTS-SMES magnets under transient overvoltages is important for the design of the longitudinal insulation of the magnets. Conventional modeling and analysis methods based on a turn conductor are not directly applicable to large-capacity HTS-SMES, due to the massive scale of the circuit model and requiring significant computational costs. In this article, a “Two-Step” lumped parametric equivalent circuit model is proposed for large magnets to simplify the calculation. Then, the transient voltage distribution characteristics of the hybrid toroidal magnet for 10 MJ HTS-SMES under lightning voltage impulse are analyzed. The effect of the turn-to-turn insulation thickness on the voltage distribution characteristics is studied. Finally, a preliminary design of the longitudinal insulation of the hybrid toroidal magnet for 10 MJ HTS-SMES is presented. The proposed simulation model was verified by sample coils, which is consistent with the simulation results.