Electric Power Principles, 2nd Edition

11Load Flow

The purpose of an electric power system is to deliver, as the name implies, electric power to a consumer. That electric power is made by a producer and carried through power system components over geographic distance from the producer to the consumer. Electric power systems very often have numerous paths over which power can flow, and the term load flow refers to techniques to understand how load flows and over which pathways.

Load flow techniques have been developed so that currents flowing in conductors may be evaluated and so that voltage distributions over the network can be determined. Load flow evaluations are required in advance of any system expansion to ensure that the expanded system will work adequately. Load flow calculations are required as part of generation dispatch to ensure that lines are not overloaded. In fact, optimal dispatch (use of generation resources) must take into account transmission and distribution system losses, which are also determined by load flow calculations. For these reasons, it is necessary to understand how electric power flows through the wires, transformers, and other components that make up the electric power system.

Even though electric power networks are composed of components that are (or can be approximated to be) linear, electric power flow, real and reactive, is a nonlinear quantity. The calculation of load flow in a network is the solution to a set of nonlinear equations.

There is still quite a bit of activity in ...