Some small isolated power systems have a grid infrastructure weakly meshed and stability could be seriously affected when a large amount of renewable energy is being flowed into the grid. In this paper critical clearing time (CCT) is studied along with the increase in renewable energies integration. This study considers the use of squirrel cage induction generators (SCIG) wind turbines. Battery energy storage systems (BESS) have been considered in order to overcome this kind of power system drawbacks. Thus, renewable energy integration improvement is achieved. Renewable energy improvement is analyzed by means of CCT values. Dynamic analysis is performed in order to determine CCT values taking into account voltage, system frequency and the amount of load shedding.