The numbers 30, 85, 86, and 87 represent a standardized terminal numbering system defined by the DIN 72552 standard, originally developed for automotive applications but now widely adopted in various industrial settings. The protection and control devices in electrical equipment can be referred to by numbers, with appropriate suffix letters when necessary, according to the functions they perform. These numbers are based on a system that is adopted by a standard for automatic switchgear by Institute of Electrical. The device numbers are enumerated in ANSI / IEEE Standard C37. These terminal designations create a universal language for relay connections. In North America protective relays are generally referred to by standard device numbers. ANSI IEEE Standard Device Numbers are below: (the more commonly used ones are in bold) 86T is a Lockout Relay for a. 1; Relay symbols and device numbers; selection from 1 MAK 590 OOB-BEN IEC 617-, IEEE C37. 2-1979 Symbols and designations ~)ymbols and designations, based on the IEC 617-series, IEC 617-7 (1983) and others Block symbols and qualifying symbols 1. General block symbols Protection.
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