Power-Flow Study is an analysis of the system’s capability to adequately supply the connected load. It is also a steady-state analysis whose target is to determine the voltages, currents, and real and reactive power flows in a system under a given load conditions. Power- Flow Study plays a key role in the planning of additions or expansions to transmission and generation facilities. The principal information obtained from the power-flow study is the magnitude and phase angle of the voltage at each bus, and the real and reactive power flowing in each line.It is especially valuable for a system with multiple load centers, such as a refinery complex.