In this thesis a version of the Kundur two-area model has been developed for Simulink and real time simulator software and hardware from OPAL-RT. This model should be used for testing the rotor angle oscillations load variations create. A review of the different control elements found in basic power systems has been reviewed and implemented. The main component that will be manipulated in the model is the active load, so a zip-load model had to be developed for Simulink to make the system work. It was necessary to build multiple models of the same figure in Simulink, one fixed step version to run in RT-lab, and one variable step to do Simulink tests on. Frequency and voltage stability are not a focus but are mentioned throughout because each of them do affect the system. The lack of secondary frequency reserves leads to never regain nominal rotor speed, and voltage stability affects the simulations done on the RT-lab model. Linear analysis of the stability was done using PST software. The linear results were compared to the variable step model. The results show that the different models behave similarly and manages to simulate what happens with the stability during load changes.