자속결합형 초전도 한류기의 인덕턴스에 따른 특성해석

Abstract

We investigated a flux-coupling type superconducting fault current limiter (SFCL) using coils and analyzed its operating characteristics. The SFCL consisted of the primary and secondary coils, which were wound in series each other through an iron core. The superconducting unit, which was based on the YBCO thin films, was connected with secondary coil in parallel. The operation of the flux-coupling type SFCL can be divided into the subtractive and the additive polarity windings according to the winding directions between the primary and secondary coils. The short-circuit currents were effectively limited by adjusting the numbers of winding turns of each secondary coil and the winding directions of the coils. The flux generated from a coil in normal operation is cancelled out by its structure and the zero resistance of the superconducting unit. In this paper, in order to compare the influence by turn numbers between coils, the turn number of the secondary coil was varied from 42 to 84 while the turn number of the primary coil was 42, 63 and 84. We confirmed that the flux-coupling type SFCL was significantly efficient to reduce initial line current after fault instant. The quench time of the flux-coupling type SFCL in the additive polarity winding was also quicker than that of the subtractive polarity winding. The fault current of the flux-coupling type SFCL with the additive polarity winding during first-half cycle after the fault was limited effectively more than that of the subtractive polarity winding. In addition, the voltage generated in the superconducting unit was also lowered by reducing power burden of the YBCO thin film in the flux-coupling type SFCL. The structure of the flux-coupling type SFCL is similar to the flux-lock type SFCL but their operational characteristics are slightly different. Each of magnetically coupled coils makes a difference according to the direction wound on an iron core. In addition, the flux-coupling type SFCL has more flexibility than that of the flux-lock type SFCL by adjusting the inductance between the primary and secondary coils. So, the operational characteristics of the flux-coupling type SFCL were investigated and compared to the flux-lock type SFCL. We confirmed that the flux-coupling type SFCL was significantly efficient to reduce initial line current than that of flux-lock type SFCL after fault instant. The flux-coupling type SFCL has more flexibility and reliability for the inductance variation than the flux-lock type SFCL in case of additive polarity winding. Therefore, it gives the application flexibility for power system when the flux-coupling type SFCL is adopted. In conclusion, the current limiting behavior of our flux-coupling type SFCL was more effective for fault current limiting operation.