Battery Energy Storage System (BESS) becomes important for many applications, including frequency regulation and control. This paper presents a comprehensive analysis of all the electro-mechanical-chemical variables involved in improving the system frequency response. It also evaluates the impact of including inertial emulation control of grid-scale BESS on the system frequency response of classical transmission systems. In order to investigate this impact, several simulations case studies are carried out, with different sudden generation outages and load disturbances with different power supply capacities. All case studies are combined with time-domain events to inspect the dynamic behavior of the frequency response of grid-scale battery. The purpose of this paper is to investigate the inertial response to design a set of algorithms to control the output of the inertial controller. Keywords—Frequency Response, Inertia Emulation Control, Grid-Scale BESS.