Voltage sag caused by the short circuit fault in transmission and distribution line. In this paper, voltage sag due to power system faults such as three-phase-to-ground, single-phase-to-ground, phase-to-phase and two-phase-to-ground are created in transmission line model for generation of different types of voltage sag. This paper describes a methodology for voltage sag generation using Matlab/Simulink. It includes fault simulations for generation of different types of voltage sag using Matlab/Simulink-based on the sim power systems toolbox.