An investigation on optimum volume of superconducting element of RSFCL considering harmonic generation

As electric power systems grow and become more interconnected, at some points, the available fault currents levels exceed the maximum short-circuit ratings of the switchgear. Superconducting fault current limiters (SFCLs) can limit the prospective short-circuit currents to lower levels, so that the underrated switchgears can be operated safely. Due to its simple structure and lower price, the resistive type superconducting fault current limiter (RSFCL) is being used widely in practical experiences. Since RSFCLs are installed to provide high levels of power quality for customers with sensitive loads, it is necessary to investigate their harmonic generation. In this paper, harmonic generation of a RSFCL installed in a distribution system is investigated considering the current total harmonic distortion (THD). Then a method is presented for determining the optimum high temperature superconductor (HTS) volume considering its harmonics generation. It is concluded that the THD reduces as the HTS element volume decreases. Also, since decrease in HTS element volume leads to decrease in limiting behavior of the RSFCL, an optimization should be achieved between the limiting behavior and the current THD level. This optimization results in the optimum volume determination of the HTS element.