Discussion of application and economics of automatic railways substations

Abstract

The automatic substation is defined, and its history is traced from the first station placed in service in 1914 to the present time. The number of automatically controlled railway stations up to the beginning of 1922 is given as 142 equipments totaling 86,000 kw. Outside the city of Cleveland, two-unit stations have been installed in but four instances, although a number of these stations are now under construction. With manually operated stations, especially in interurban work, the location of stations is determined by local conditions, availability of labor, etc. rather than by load conditions. But with the advent of the automatic substation it is possible to locate stations more nearly at the proper points to take care of the system loads giving improved voltage conditions with a minimum of feeder copper. Accessory advantages, in addition to the labor saving item, include a reduction in running light losses, a reduction in distribution losses, lower cost of substation and, in some cases, an actual retirement of existing feeder copper. An example is cited of a double track line 80 miles long with figures from a report which shows a net annual return on the investment, including 6 per cent interest, of 34.9 per cent. The labor saving is based on two twelve-hour shifts, and it is further calculated that with three eight-hour shifts the annual saving would be increased by an appreciable figure. The Des Moines City Railway was the first system to install a group of automatic substations for city service, while the Cleveland Railway Company is given credit for installing the first two-unit automatic substation for metropolitan railway service. Reasons are advanced for using two-unit stations in Cleveland in contrast to the general practise of employing single-unit stations in interurban work. Emphasis is laid on the necessity for absolutely uninterrupted service in a large city system, even under such emergencies as either an interruption of the a-c. power supply, or short circuit due to breaking of the trolley wire. A further comparison between the operation of manual and automatically controlled substations is taken from one of the surveys made in Cleveland. The tabulation indicates a net annual saving of $13,900 per year for the automatic over the existing stations. As to the reliability of automatic control equipments, conclusion is reached that an operator is very unlikely to anticipate trouble, whereas with automatic control the protective equipment operates so successfully that various interruptions are a rare occurrence. There is also the possibility of an operator making an error in judgment, thereby causing trouble which might not otherwise occur. A further consideration which should not be overlooked is the possibility of loss of operators due to strikes or other causes. An outline of the equipment used in the Cleveland stations is given with special reference to outgoing feeders and the proposed method of eliminating current-limiting resistance. Description is also given of the remote control equipment now being manufactured, which will enable the several automatic stations to be supervised from a central point by a dispatcher.