{"schemaVersion":1,"slug":"87g-generator-differential-protection","name":"Generator differential protection","kind":"function","abbreviation":"87G","aliases":["generator differential","generator diff","ANSI 87G","IEEE 87G"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEEE / ANSI","Manufacturer"],"summary":"Compares current measurements bounding the selected generator differential zone.","description":["Compares current measurements bounding the selected generator differential zone.","The drafting record should connect this function to the generator terminal and neutral-side CT connections, then trace the generator differential zone and unit tripping 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 (SEL public device-number table). Suffixes are not universal equivalences across products, and this reference supplies neither a protection setting nor certification of the selected scheme."],"readingNotes":["Identify the generator terminal and neutral-side CT connections.","Trace the generator differential zone and unit tripping matrix."],"drawingChecklist":["Label the generator terminal and neutral-side CT connections.","Cross-reference the generator differential zone and unit tripping matrix.","Retain the complete suffix, selected device tag and manufacturer manual revision."],"distinction":"G denotes generator in this differential application; it should not be interpreted using the ground-current meaning of 50G.","facts":[{"label":"Function designation","value":"87G"},{"label":"Base function","value":"87 — Differential protection"},{"label":"Published mapping","value":"SEL public device-number table"},{"label":"Suffix scope","value":"Application or manufacturer specific; check the complete drawing legend and selected device manual."}],"references":[{"sourceId":"pub-function-sel-numbers","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/87g-generator-differential-protection","illustration":{"url":"https://eloragrid.ai/library/illustrations/87g-generator-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-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 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."}]}