매트릭스형 초전도 전류제한기의 고장전류 해석

Abstract

We fabricated the matrix type superconducting fault current limiter (MFCL) based on YBa₂Cu₃O7(YBCO) thin films. In case of YBCO thin films, they have high current density and the high indexing value. Then, we could make the MFCL with compact size and high switching speed. This MFCL consisted of trigger matrix part and current limiting matrix part. The level of applied voltages is able to be increased by using the matrix type array of superconducting elements. We designed the basic 1×2, 1×3, and 1×4 MFCL modules. The current limiting operation and voltage distribution between superconducting elements were compared when the applied voltages were 160V, 320V and 480V, respectively. A slight difference in critical current density among elements produced significantly unbalanced power dissipation among elements. The unbalanced quenches give the difficulties in increasing the voltage ratings of power system. In order to promote the quench stability, this MFCL could be operated by inducing fast quenching behavior of superconducting elements through the magnetic field. However, when a fault occurred, the current limiting characteristics are influenced by a impedance of the shun coil. So, we connected a resistor with the shunt coil in series from 5Ω to 20Ω. The test results showed that higher resistor performed more effective for current limiting operation at first and second cycle after a fault. However, test results showed slightly unbalanced power dissipation among the elements. The imbalance was removed by increasing applied voltage and connecting a shunt coil with a resistor in series. Also, the quench starting point and the generated resistance of a element could be controlled by adjusting turn numbers of magnetic coil and the applied voltage. The magnetic filed of the trigger part have an influence on response time (Tq) and the critical current densities of superconducting elements. As a result, these module structures induced fast quenching of the superconducting elements quick detection of the fault current.