Electrical Engineering ⇒ Topic : Selection of size and number of generating units

SELECTION OF SIZE A.ND NUNIBER OF GENERATING UNITS

The following points are worth noting :

The most appropriate way of deciding the size and number of generating sets in a station is to select the number of sets in sucrh a way so as to fit in the load curve as closely as possible, so that the plant capacity may be used efficiently.

Extra spare capacity is not desired as it increases the capital expenditure.

The main aim should be to have units of different capacities which will suitably fit in the load curve so that most of the generators when in use can be operated at nearly full load.

The equipment prices are usually compared on the basis of price per unit of capacity, usually termed as 'unit price'. The unit price decreases as the capacity of the machine increases. This is the main reason for adopting a large size generating unit in power plants. Figure shows the general trend and trend of the major cost components in building a given type of machine.

                   Figure Variation of costs of power plant versus its capacity