Planning and operation of a large power pool

Most of the electric power supply systems in the United States are interconnected to provide more reliable service and economy of operation. The majority of these interconnections consist, generally, of tie lines between neighboring utility systems, with contracts between the parties providing for sharing of benefits or for operating procedures. This article discusses how interconnections evolved into fully coordinated power pools, and the benefits resulting from this coordination. Of particular interest is the Pennsylvania-New Jersey-Maryland Interconnection, the largest such pool in the country. Dating back to 1927, it established a successful pattern for the coordination of utility systems.