Economic Dispatch Problem

Economic load dispatch concerns with the operating
cost rather than the fixed cost
Only fuel cost is considered in the study where all
other costs that are depend on the generated power
will be included in the expression of the fuel cost
Obviously, the cost of fuel is concerned since thermal
plants are assumed
An early approach of power dispatch was to supply
power from the most efficient plant till the point of
maximum efficiency and then from the next most
efficient plant and so on

Another approach was to load the machines so that

all units have the same incremental cost of
production
However, the locations of power plants and the
trans-mission losses are not considered
Generating power in far plants requires supplying the
transmission losses in addition to the load demand
Economic distribution of load demand among
generating units necessitates expressing the cost as
a function of the generated power
The performance curve of boiler-turbine-generator
set is required, which is called input-output curve