This research paper elaborates detailed significance of stabilizing the core parameters of generated power, i.e., Frequency and Voltages. In addition, VRT capability of integrated renewable energy sources (RES) from existing conventional power systems is compared. As the greenhouse effect is rising rapidly, sustainable power systems are required which could eliminate global energy crisis. This paper has provided precise results of the behavior of conventional power system after integrating Renewable Energy Sources (RES) on existing IEEE-39 bus system, simulations are carried out by Dig SILENT Power Factory software and their transient responses are recorded after introducing large disturbances i.e. creating short circuit events on different buses. Results obtained from RES are compared with the default Synchronous Machines results.