Fig. 2,773.—Westinghouse three cylinder gas engine, direct connected to dynamo, showing application of gas engine drive for small direct connected units.
Consequently, persons desiring electrical power were in the majority of cases forced to install their own apparatus for producing it, this being the origin of isolated plants.
From the nature of the case it is evident that an isolated plant is as a rule smaller and more simple in construction than a central station, and in consequence much more readily operated and managed. It is generally owned by a private individual or a corporation and operated in conjunction with other affairs of a similar character. A basement or other portion of a building is usually set aside in which the necessary apparatus is installed.
Fig. 2,774.—General Electric 25 kw., gasoline electric generating set for lighting and power. The engine has four cylinders 7¼ × 7½, and runs at a speed of 560 revolutions per minute. The total candle power capacity in Mazda lamps is 20,000. The ignition is by low tension magneto, coil and battery. Carburetter is of the constant level type to which gasoline is delivered by a pump driven by the engine. Forced lubrication; five crank shaft bearings babbitted; valves in side; overall dimensions 96 × 34 × 60 high; weight 5,000.
Although electricity is now transmitted economically to great distances from central stations, there is still a field for the isolated plant.
The average type of isolated plant has enlarged from a small dynamo driven by a little slide valve engine located in an out of the way corner to direct connected generators and engines of hundreds and even thousands of horse power assembled in a large room specially adapted to the purpose.
In the more modern of these, the electrical outputs are each frequently equal to that of a town central station of respectable size, and the auxiliary equipments are similar in every particular. As a matter of fact, in certain modern isolated plants the only feature that distinguishes them from central stations is that in the former case the owner of the plant represents the sole consumer and conducts other business in connection with it, whereas in the latter case there are a large number of consumers uninterested financially in the enterprise, which is itself generally owned and operated by a company conducting no other business.