Abstract –The advancement in science and engineering led to the development of relays, started by electromechanical, and followed by solid-state, and lately digital and numerical relays. Numerical relays are the result of the application of microprocessor technology in the relay industry. This paper describes an approach for detailed modeling of a numerical distance relay using MATLAB/SIMULINK. The distance relaying is for use in a modeled EHV transmission system. A section of 400 kV, 350 km length transmission lines is chosen for the case study. The numerical relay is modeled having Mho characteristics suitable for three-zone distance relaying. A set of tests were performed to investigate the applicability and consistency of the developed relay model. The results showed that the numerical relay model respond satisfactorily to fault incidents and in accordance with the expected results of the performed tests.