The thesis deals with the modeling and simulation of distance relays in ATP - EMTP. Transmission line which is 125.6 miles long operates at 60 Hz and 115 kV line voltages are simulated in ATP - EMTP. The first part of the thesis discusses the implementation and simulation of the ATP - EMTP model for microprocessor based mho distance relay using angle comparator method in the network. The model includes the modeling of input filter, sample and Fourier fundamental frequency detector, which process the input for mho distance relay model. A number of simulations of single line to ground faults (SLGF) with different fault locations were carried out to verify the correct operation of the relay based on the developed protection scheme. The results of the simulation show the operation of the relay based on its protection scheme and its response time related to the fault locations. The study is also extended to the double line to ground fault for the same purpose. The second part of the thesis discusses the model for an electromechanical mho distance relay, which includes the modeling of current transformer (CT) and capacitive voltage transformer (CVT). A validated ninth-order mathematical model of the electromechanical Mho distance relay is constructed in ATP - EMTP to observe the dynamic behavior of the relay during a critical fault. For that purpose, SLGF were tested in critical locations which is very close to the relay. The results show how CT saturation and CVT transient influence the relay operation. The applied procedure can be used for testing of distance protection performance against single phase fault currents.