Transactions of the American Institute of Electrical Engineers Volume 32, PT. 2 (Paperback)

This historic book may have numerous typos and missing text. Purchasers can download a free scanned copy of the original book (without typos) from the publisher. Not indexed. Not illustrated. 1913 Excerpt: ...of single converting units has increased from 250 kw. to 3500 kw., and fortunately the building art has so advanced that head-room of from 15 to 26 ft. (4.5 to 7.9 m.) has been made available in some of the sites more recently secured. In the heart of Chicago, practically within the "loop," there are ten substations either in service or about to be commissioned which have a combined capacity of 42,000 kw. in converting apparatus or storage batteries, all operating on the Edison three-wire system, eight of which, with a total capacity of 29,000 kw., are of this sub-grade type. One of the latest substations has an ultimate capacity of four 3500-kw. and one 2000-kw. synchronous converters; one of the earliest has eight 500-kw. and four 1000kw. converters. The district has an area of only 0.81 sq. mi. (2.1 sq. km.) and a connected load of 1,940,000 lamps (50-watt equivalent), a maximum last year of 31,000 kw. and an annual load factor of 32 per cent. Fig. 1 shows the 24-hour load on the day of maximum kw. in the winter of 1912, and Table I shows the annual kw. increment, an interesting table, in which may be discerned indiscriminate periods of great business expansion and depression and, faintly, the advent qf the tungsten lamp. Fig. 1--Low-tension Down-town Direct-current Load On Day Of Maximum Output--Dec. 16, 1912 Devoid of all exterior attractiveness, these converting substations may be viewed from the engineer's standpoint as a series of large, deep pits surrounded by concrete walls, upon which devolves the duty of resisting the inward thrust of the TABLE I Per Cent Of Increase Of Down-town Low-tension Maximum Load Per cent abutting earth and of keeping out the surface and sub-soil water, bottomed with a layer of concrete which must be heavy enou...