Buana Energi Surya Persada intend to expand its existing PV Farm capacity to max. power output. This PV Farm will be equipped with BESS and expected to be able to deliver power continuously whole day, with the main objective to reduce the usage of diesel generators in the system (supporting the de-dieselization program). To ensure a smooth operation of soon to be constructed PV+BESS, grid impact study for the plant interconnection to the power system is essential, by conducting the study we will be able to determine the optimum BESS sizing and to assess the technical feasibility of the Solar power plant interconnection from the electrical aspect, also an additional running with considering degradation for the study.