These standardized numerical codes, ranging from 1 to 99, represent specific functions of protective relays, associated devices, and control equipment in electrical power systems, facilitating clear communication and consistent documentation across the industry. There are two methods for indicating protection relay functions in common use. The functions are supplemented by letters where amplification of the function is required. The other is given in IEC 60617 and uses. The widely used United Sates standard ANSI/IEEE C37. Even in those parts of the world where IEC standards are predominate, the use of ANSI numbering. In electric power systems and industrial automation, ANSI Device Numbers can be used to identify equipment and devices in a system such as relays, circuit breakers, or instruments. 2 Standard for Electrical Power System Device Function. We'll explore symbols for various relay types—all-or-nothing, measuring, and static—looking at general forms as well as application-specific variants.
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