Power flow studies, commonly known as load flow, form an important part of power system

analysis. They are necessary for planning, economic scheduling and control of an existing system as

well as planning its future expansion. The problem consists of determining the magnitudes and phase

angle of voltages at each bus and active and reactive power flow in each line.

In solving power flow problem, the system is assumed to be operating under balanced

conditions and a single-phase model is used. Four quantities are assumed at each bus. These are voltage magnitude v, phase angle  , real power P, and reactive power Q.The Newton Raphson method of load flow analysis is an iterative method which approximates the set of non-linear simultaneous equations to a set of linear simultaneous equations using Taylor’s series expansion and the terms are limited to first order approximation.