The paper describes the issue of protecting dual-system high-voltage transmission lines using distance protection. The analysis of the calculation of the measured impedance of the distance protection for different types of short circuits is presented and its visualization in the R, X coordinate system. The criteria for selecting the distance protection settings (1st and 2nd stage) of dual-system overhead lines where electromagnetic coupling is present in the neutral system are also presented in detail. The criteria consider three different possible switching states of the dual-system transmission line and analyze the error of the measured impedance with respect to the switching state and the initial range setting, especially for the 1st stage and especially for the 2nd stage of distance protection. The analysis of the distance protection settings with the verification of selectivity and sensitivity is presented on a specific example of a dual-system line in a transmission network.