The number of high power users operating in the subsystem will rise in line with economic expansion, which will result in overloading conditions on the inter bus transformers (IBT). To overcome the overload condition of 500 kV/150 kV (IBT) in the X area due to load forecasting, 2×400 MW power plant is planned to be moved from 500 kV bus into 150 kV bus. This research aims to analyze the power flow and short circuit study before and after the migration is implemented. The method used in this research is a simulation using ETAP software. From the results of the power flow study, it can be concluded that the migration of 2 units of power plant can reduce the load on IBT 1 and IBT 2 both under normal conditions and during contingency in one of IBTs. In addition, it also increases the bus voltage profile, reducing losses in the 150 kV sub-system area. From the results of the short circuit study, migrating 2×400 MW power plant units, is safe in terms of equipment durability.