{"schemaVersion":1,"slug":"87r-restrained-current-differential-protection","name":"Restrained current differential protection","kind":"function","abbreviation":"87R","aliases":["restrained differential","percentage differential","ANSI 87R","IEEE 87R"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEEE / ANSI","Manufacturer"],"summary":"Uses a differential operating quantity with restraint in the cited transformer-relay application.","description":["Uses a differential operating quantity with restraint in the cited transformer-relay application.","The drafting record should connect this function to the differential-zone CT inputs and restraint-measurement definitions, then trace the restrained element and transformer trip matrix. Keep the complete designation and equipment tag together so that the SLD, relay logic and terminal schedule describe the same implementation.","The cited mapping is a public manufacturer example (Eaton ETR family). Suffixes are not universal equivalences across products, and this reference supplies neither a protection setting nor certification of the selected scheme."],"readingNotes":["Identify the differential-zone CT inputs and restraint-measurement definitions.","Trace the restrained element and transformer trip matrix."],"drawingChecklist":["Label the differential-zone CT inputs and restraint-measurement definitions.","Cross-reference the restrained element and transformer trip matrix.","Retain the complete suffix, selected device tag and manufacturer manual revision."],"distinction":"Eaton's 87R mapping is restrained differential; R here does not mean the calculated residual-current input used in 50R.","facts":[{"label":"Function designation","value":"87R"},{"label":"Base function","value":"87 — Differential protection"},{"label":"Published mapping","value":"Eaton ETR family"},{"label":"Suffix scope","value":"Application or manufacturer specific; check the complete drawing legend and selected device manual."}],"references":[{"sourceId":"pub-function-eaton-transformer","relevance":"Public primary-source function or application mapping used to identify this designation; wording and drafting notes are original."},{"sourceId":"ieee-functions","relevance":"Device-number and suffix convention. This page is not a reproduction of the full licensed standard."}],"related":["87-differential","current-transformer"],"artwork":"pub-function-box","publishedOn":"2026-10-13","updatedOn":"2026-10-13","provenance":"independent-public-research","url":"https://eloragrid.ai/protection-functions/87r-restrained-current-differential-protection","illustration":{"url":"https://eloragrid.ai/library/illustrations/87r-restrained-current-differential-protection.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-eaton-transformer","title":"ETR-4000 and ETR-5000 transformer protection function tables","publisher":"Eaton","url":"https://www.eaton.com/us/en-us/catalog/electrical-circuit-protection/transformer-relays.html","type":"manufacturer","scope":"Public transformer-relay mappings including restrained/unrestrained differential, restricted ground differential, main and auxiliary voltage inputs, and measured/calculated earth-current inputs.","checkedOn":"2026-10-13","reuse":"link-only","relevance":"Public primary-source function or application mapping used to identify this designation; wording and drafting notes are original."},{"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":"Device-number and suffix convention. This page is not a reproduction of the full licensed standard."}]}