The calculation of ac short-circuit currents, essential to the selection of adequately rated protective devices and equipment in industrial and commercial power systems, is becoming increasingly important to the system designer. Today, power systems carry larger blocks of power, are more important to the operation of the plant and building, and have greater safety and reliability requirements. Meeting these requirements necessitates the fulfillment of certain criteria, including the use of adequately rated equipment.
This report outlines state of-the-art industrial power system engineering practices which should be especially valuable to industrial plant engineers and electricians, industrial power application engineers and others who are involved with the planning of electrical facilities for industrial plants or commercial buildings.
The method of short-circuit-current calculation has been selected, so that adequate ratings of all the air circuit breakers were obtained. Fault protective devices were selected to maintain proper relay coordination throughout the system. These devices has been selected and set so that only the device nearest a fault opened to clear the fault without affecting larger devices nearer the source of power or causing a wider outage than the minimum.