Increasing wind generation causes displacement of conventional power plants with Synchronous Generators in electrical power systems. This condition leads to less inertia, less controllability and a degraded damping performance in the electrical systems. Studies of stability of the power system attempt to analyze this issues. Rotor angle stability studies using real time digital simulation requires the use of data mining to obtain an insight about the coherency of the system with the variation of the time series data. However, the limitations of the simulation systems as well as the magnitude of the models can lead into difficult study scenarios. By modeling the power systems in real time simulators, electrical studies can be performed faster than with conventional offline simulators. In this thesis project, the Britain baseline system was modeled in the Real Time Digital Simulator (RTDS) using as a starting point and initialization reference, the electrical power model developed for the simulator Power Factory. The model then was reduced using coherency analysis by clustering time-series-data. The same modeling considerations were applied for implementing future scenarios of the GB in the RTDS. For reduction purposes, three main areas describing the North, Central, and South parts of the system were considered in the GB model. The results show that while the area of study is considered constant the other two areas can be replaced by the coherent areas. Thus, less use of racks is required for analyzing the model in the simulator. This study contributes to the analysis of the power electrical systems, by providing valuable insights in how to reduce electrical models for their study in the RTDS.