Improvement of Power System Stability by Use of Superconducting Fault Current Limiter With ZnO Device and Resistor in Parallel

Superconducting fault current limiters (SCFCLs) are expected to improve the reliability and stability of power systems. SCFCLs can be classified into R-types (resistive) and L-types (inductive) by the fault current limiting impedance. An L-type FCL is more effective in suppressing the voltage drop during a fault. On the other hand, a R-type FCL is more effective in consuming the acceleration energy of generators at the fault. Both functions lead to the improvement of the transient stability of the power system. We have proposed and fabricated the FCL unit, which is expected to have both functions. It consists of an inductive superconducting fault current limiter with a resistor and a ZnO device in parallel. In this paper, the simulation analysis on one machine and an infinite bus transmission system including the proposed FCL unit was carried out. EMTP (electro-magnetic transients program) was used in order to analyze the power system characteristics of the FCL unit. A rotor angle of the generator and a critical fault clearing time were analyzed to evaluate the effects of the FCL unit on the improvement of the transient stability of the model power system. A contribution share of the voltage drop suppression and the acceleration energy consumption to the improvement of the power system stability were clarified with various conditions, such as, generator output and fault clearing time.