In this research, a novel fault-location algorithm for transmission lines including the unified power-flow controller (UPFC) is proposed. Since this method does not utilize model of the UPFC, the errors resulting from the fault interval model of the UPFC are avoided. In addition, the new technique does not require proposing a selector to select fault section with respect to the UPFC location. This method uses synchronous data gathered from both ends of the transmission line and takes advantage

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... f the distributed parameter line model in time domain. One quadratic equation is obtained, assuming that the fault is located on the left-hand side of the UPFC. The same procedure is applied for the assumed fault on the right-hand side of the UPFC and another quadratic equation is achieved. These two equations are used to derive an optimization problem that the location of fault is calculated by solving this problem. A 300-km/500-kV transmission line, including a UPFC simulated in MATLAB/Simulink, has been used to evaluate the performance of the new method. The obtained results show the accuracy of the proposed algorithm. Index Terms-Distributed parameter line model, fault location, synchronous sampling, time domain, unified power-flow controller (UPFC).