{"schemaVersion":1,"slug":"12-overspeed-device","name":"Overspeed device","kind":"function","abbreviation":"12","aliases":["overspeed relay","high speed protection","ANSI 12","IEEE device 12"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEEE / ANSI"],"summary":"Responds when machine speed exceeds the documented operating criterion.","description":["Responds when machine speed exceeds the documented operating criterion.","In a drafting package, connect this reference to the speed sensor and shaft or machine identity. The associated drawing should trace the overspeed shutdown or alarm path; the number identifies the role and does not specify the terminal arrangement, ratings or operating settings."],"readingNotes":["Identify the speed sensor and shaft or machine identity.","Trace the overspeed shutdown or alarm path."],"drawingChecklist":["Label the speed sensor and shaft or machine identity.","Cross-reference the overspeed shutdown or alarm path.","Identify the device tag, manual revision and logic drawing that define this implementation."],"distinction":"Electrical frequency can relate to speed, but an 81 element is not universally equivalent to mechanical overspeed protection.","facts":[{"label":"ANSI / IEEE function number","value":"12"},{"label":"Drawing context","value":"The speed sensor and shaft or machine identity"},{"label":"Application scope","value":"Protection or apparatus-control role; exact implementation is defined by the equipment documentation."}],"references":[{"sourceId":"pub-function-sel-numbers","relevance":"Public manufacturer number/name association. Drafting explanations are independently written."},{"sourceId":"ieee-functions","relevance":"Normative device-number publication; exact edition wording and compliance require the licensed standard."}],"related":["generator","52-ac-circuit-breaker"],"artwork":"pub-function-box","publishedOn":"2026-10-13","updatedOn":"2026-10-13","provenance":"independent-public-research","url":"https://eloragrid.ai/protection-functions/12-overspeed-device","illustration":{"url":"https://eloragrid.ai/library/illustrations/12-overspeed-device.svg","scope":"Original educational concept; not an official standard graphic or product footprint","license":"https://creativecommons.org/licenses/by/4.0/"},"sources":[{"id":"pub-function-sel-numbers","title":"ANSI device-number and suffix reference table","publisher":"Schweitzer Engineering Laboratories","url":"https://selinc.com/pt/products/tables/ansi/","type":"manufacturer","scope":"Public Portuguese-language base-number and application-suffix table. Used to cross-check public number associations. Application-specific and historical labels need the selected drawing legend; this table is not a substitute for the licensed IEEE standard.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public manufacturer number/name association. Drafting explanations are independently written."},{"id":"ieee-functions","title":"IEEE C37.2-2022: power-system device function numbers","publisher":"IEEE","url":"https://ieeexplore.ieee.org/document/9984140","type":"standard","scope":"Device function numbers, acronyms and contact designations. The full publication may require access through IEEE.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Normative device-number publication; exact edition wording and compliance require the licensed standard."}]}