The design and operation of a metropolitan electrical system from the viewpoint of possible major shutdowns

W. J. Lyman (Duquesne Light Company, Pittsburgh, Pa.): The so-called “loose link” system described in Mr. Dean's paper is an excellent example of a sound principle of system design which strikes an economic balance between two opposing relationships. In general, the more extensive the generation and distribution system which runs tied together in a close network, the better is the generating economy and the more efficiently are the circuit capacities utilized. In contrast to this, as the extent and complexity of the network is increased, the protection becomes more expensive, short-circuit currents require larger breakers, and many of the operating problems become difficult, particularly during trouble. These two opposing tendencies fix an economic limit to the size of the system which should be closely tied together. Following this principle, a large system can be divided into two or more parts, loosely linked together, without any over-all sacrifice in economy and with much better operating characteristics. Relatively high reactances can be placed at natural division points which normally carry little load but which can still take advantage of the diversity between load areas through moderate interchange of power.