Fault identification of double circuit lines

The technique for identifying fault types on single circuit lines, suggested by Ferrero et al. (1993) is modified to be suitable for protecting double circuit lines. The modified technique is based on estimating the Fourier coefficients of double circuit line currents using the recursive least square identifier. The sequence components are obtained by a linear transformation of the fundamental frequency phase currents of each circuit. The fuzzy logic inference system processes these components to identify fault type. The computer simulation test results indicate the possibility of using the suggested technique as an effective tool for high speed digital relaying