Transformer Substation

—In an electric railway system extending over a considerable area, it is customary to distribute the power in the form of high tension alternating current, and transform it by means of step-down transformers and rotary converters to direct current for feeding the trolley wire. The apparatus for transforming is located in substations conveniently situated for meeting the demand for current at different sections of the line. Portable substations consisting of specially designed cars with complete substation equipment are frequently employed to provide for temporary exce ive use of portions of the line, as at resorts or at the time of sporting events, etc.