Coordinating overcurrent protection devices

Abstract

Distribution, substation, and plant engineers can benefit from using an overcurrent protection program in commercial, industrial, and utility applications to aid in clearing temporary faults and isolating permanent faults. In the time it normally takes to check one coordination scheme manually, dozens of alternatives can be evaluated using a graphics-oriented program, because the engineer receives immediate feedback for quick decision-making. It is well known that accurately coordinating overcurrent protection devices can minimize or prevent equipment damage, and electrical power service to customers can be greatly improved. In addition to assisting experienced engineers, an overcurrent protection program is an excellent training tool for new engineers. One such tool, V-PRO II, is a second generation program that is Windows-based. An extensive protective device library and an interactive on-line diagram for direct data entry are key new features. Easily identifiable icons are used along with pop-up menus and dialog boxes to simplify command selection. HELP can be accessed any time, and information on a specific topic can be retrieved quickly using hypertext. The program contains two separate windows: a one-line diagram with symbols for buses, lines, components, and protection equipment; and a time-current worksheet with time-current characteristic curves for both phase and ground coordination.