Impact of Active Superconducting FCL on Distance Protection in Nine Bus

Abstract

In this paper, Active Superconducting Fault Current Limiters (ASFCLs) has been introduced in the existing nine bus ring system to validate prompt reduction in fault current magnitude. Instigation of FCL in rapidly expanding transmission and distribution network supports existing installed equipment. ASFCL uses converter in association with superconducting transformer to decrease fault current with its inception instantaneously. In nine bus ring system, with and without ASFCL, various faults are simulated, sampled and processed using MATLAB/Simulink. The mitigation of current during LG fault has been observed to be effective with ASFCL placement near the generating buses in the existing system. This inclusion of ASFCLs in the existing system appends the impedance seen by the distance relays affecting its characteristics operation and the protection scheme. Resistance, reactance, impedance and phase angle as seen by the relay have been computed using fundamental component of the voltages and currents, extracted by applying Discrete Fourier Transform (DFT) on sampled data. The change in the impedance and its component have been tabulated and plotted without and with ASFCL for different types of fault with respect to distance between fault points and relay location. The zone settings of protected transmission line, need to be modified as per appended reactance and impedance seen by distance relay with inclusion of SFCL to prevent maloperation.