5.2 CONTROL AREA CONCEPT

We now consider the problem of control and power output of the generator at constant frequency.

In olden days, electric power systems were usually operated as individual units. Due to demand for larger bulk of power and increased reliability, interconnection of neighboring plants is done. It is advantageous economically because fever machines are required as reserve for operation at peak loads (reserve capacity) and fewer machines are needed to be run without load to take care of unexpected jumps in load(spinning reserve). Therefore, all generating plants are interconnected to form successively a state grid, a regional grid and a national grid. Load dispatch centers are required for the control of power flow in there grids.

It is feasible to divide a very large power system, say a national grid into sub-areas in which all the generators are assumed to tightly coupled, i.e. they swing in unision with change in load or due to speed changer setting. Such an area, where all the generators are running coherently, is termed as a “control area”.

All generators in this area constitute a coherent group i.e., all generators speed up or shutdown simultaneously.

Consider a single turbo generator system supply to an isolated load. The speed governing system controls the real power flow in the power system.