Abstarct: Identifying the location of faults in transmission lines and quickly fixing them increases network reliability and reduces outage duration. Stitched lines are used as a special type of double-circuit transmission lines due to economic issues and the lack of bays in high-voltage substations in the network. These lines are like regular double-circuit lines, but they are connected to a bay at both ends. This makes it impossible to measure the current of each circuit separately, making fault location challenging. One of the methods used in fault location is the impedance-baxsed method, which is simple, efficient, and accurate. Impedance-baxsed fault location methods for double-circuit lines require separate currents of both circuits, but it is not possible to access the currents of both circuits in stitched lines. Therefore, in this thesis, two impedance-baxsed fault location methods are proposed using two-terminal current data for locating asymmetrical faults and using one-terminal current data for locating single-phase-to-ground faults in stitched transmission and superdistribution lines. Simulation results indicate that the proposed methods have appropriate accuracy in fault location under the conditions of changing fault resistance, fault onset angle, fault clearing time, sampling frequency, noise, uncertainty of source and line Thonen impedances, and CT saturation. According to the obtained results, the highest average inaccuracy in all the cases investigated using the two-terminal method is less than 0.83 percent. Also, the average inaccuracy of the single-terminal method is obtained below 1 percent in more than 82 percent of the evaluated cases, and its highest inaccuracy is less than 1.5 percent.