{"schemaVersion":1,"slug":"21yn-admittance-based-earth-fault-protection","name":"Admittance-based earth-fault protection","kind":"function","abbreviation":"21YN","aliases":["earth fault admittance","EFPADM","ANSI 21YN","IEEE 21YN"],"category":"measurement-protection","drawingTypes":["SLD","Schematic"],"referenceFamilies":["IEEE / ANSI","Manufacturer"],"summary":"Uses earth-fault voltage and current relationships to assess an admittance-based directional criterion.","description":["Uses earth-fault voltage and current relationships to assess an admittance-based directional criterion.","The drafting record should connect this function to the residual voltage and residual current measurements and neutral-earthing method, then trace the earth-fault operating element and selected feeder trip. 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 (ABB Relion 620 function mapping). Suffixes are not universal equivalences across products, and this reference supplies neither a protection setting nor certification of the selected scheme."],"readingNotes":["Identify the residual voltage and residual current measurements and neutral-earthing method.","Trace the earth-fault operating element and selected feeder trip."],"drawingChecklist":["Label the residual voltage and residual current measurements and neutral-earthing method.","Cross-reference the earth-fault operating element and selected feeder trip.","Retain the complete suffix, selected device tag and manufacturer manual revision."],"distinction":"ABB documents 21YN for EFPADM; this admittance earth-fault function is distinct from a generic line-distance zone.","facts":[{"label":"Function designation","value":"21YN"},{"label":"Base function","value":"21 — Distance protection"},{"label":"Published mapping","value":"ABB Relion 620 function mapping"},{"label":"Suffix scope","value":"Application or manufacturer specific; check the complete drawing legend and selected device manual."}],"references":[{"sourceId":"pub-function-abb-mappings","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":["21-distance-protection","current-transformer"],"artwork":"pub-function-box","publishedOn":"2026-10-13","updatedOn":"2026-10-13","provenance":"independent-public-research","url":"https://eloragrid.ai/protection-functions/21yn-admittance-based-earth-fault-protection","illustration":{"url":"https://eloragrid.ai/library/illustrations/21yn-admittance-based-earth-fault-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-abb-mappings","title":"Relion 620 series: published protection function and designation mappings","publisher":"ABB","url":"https://techdoc.relays.protection-control.abb/r/620-series-IEC-60870-5-103-Point-List-Manual/2.0-FP1-IEC/en-US/Functions-codes-and-symbols","type":"manufacturer","scope":"Manufacturer mapping of function names, IEC identifiers and ANSI labels. These are examples for a documented product family, not universal equivalences between standards or products.","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."}]}