1. Generating stations;
2. Distributing stations;
3. Converting stations.
and with respect to the form of power used in generating the electric current, generating stations may be classed as
1. Steam electric;
2. Hydro-electric;
3. Gas electric, etc.
Central Stations.—It must be evident that the general type of central station to be adapted to a given case, that is to say, the general character of the machinery to be installed depends upon the kind of natural energy available for conversion into electrical energy, and the character of the electrical energy required by the consumers.
This gives rise to a further classification, as
1. Alternating current stations;
2. Direct current stations;
3. Alternating and direct current stations.
The alternators or dynamos may be driven by steam or water turbines, reciprocating engines, or gas engines, according to the character of the natural energy available.
Fig. 2,705.—Elevation of small station with direct drive, showing arrangement of the boiler and engine, piping, etc.