Longitudinal Insulation Design of Solenoid Type Superconducting Fault Current Limiter

The longitudinal insulation analysis method is developed for the solenoid type windings. The distributed lumped model is proposed to calculate the response under high-frequency transient impulse for the solenoid type superconducting fault current limiter (SFCL). Various simulation results according to the proposed model are consistent with the experimental results, which indicates that the developed model is effective for describing such kind of “noninductive” type solenoid windings. Therefore, the longitudinal insulation of the 20 kV/400 A SFCL has been analyzed by this method. The initial voltage distribution and the standard lightning impulse response for different turn-to-turn distances of the superconducting windings are calculated. According to the simulation results, the most severe impact is at the time when the lightning impulse wave is applied to SFCL, and the first and last turns of the winding endure a very high voltage drop at this moment. Considering the insulation margin and size, the turn-to-turn distance of 4.5 mm is taken as the longitudinal insulation distance of the SFCL.