The rise of Renewable Energy Sources (RES) such as wind and solar power, creates new challenges for electric power systems. One of these challenges occur in Frequency Containment Reserves (FCR) on power system because of decreasing system inertia from RES. The purpose of FCR is to regulate the system frequency after a disturbance that gives rise to a Rate of Change of Frequency (RoCoF) and an Instantaneous Frequency Deviation (IFD). Conventional electricity production such as hydro and nuclear power have a contribution for the amount of inertia in the system, while RES lack this contribution of inertia.This paper studies different cases of amount of inertia to understand the impact of lower amount of inertia caused by RES on power system. A power system was simulated and the IFD and SteadyState Frequency Deviation (SSFD) of the system were examined as the nuclear powers were substituted by wind powers. The results showed that a large amount of inertia implies a small IFD and vice versa.Furthermore, this paper also studies Battery Energy Storage System (BESS) as a power support for FCR when using RES. The conclusion for the impact of the battery was to use high injected power and triggering frequency level (TLF) and vice versa to get an acceptable IFD. In other words, this means that it is possible to keep the IFD within predefined limits by using batteries and identify the appropriate range of battery control settings.