Power flow (PF) is an evaluation tool for operation and planning for determining the steady condition of operation. The feasibility of PF solution is a necessary condition for pricing theory and stability analysis as well as further robust optimal power flow program. Therefore stability for necessity of the performance of PF tools becomes very important. PF studies are routinely used in planning, control, and operations of existing electric power systems as well as planning for future expansion. Satisfactory operation of power systems depends upon knowing the effects of adding interconnections, connecting new loads, introducing new generating stations, or constructing new transmission lines before they are installed. In power system operations, a PF study is used to evaluate the state of the system under a given operational condition and to allow the operator to detect overloads and evaluate transfer limits. The extensive calculations required for both PF voltage determination requires the use of specialized computing tools.