21
Distance protection
Uses measured voltage and current to assess an electrical distance or impedance characteristic.
Protection functions
Protection functions · 21YN
Admittance-based earth-fault protection
Uses earth-fault voltage and current relationships to assess an admittance-based directional criterion.
SLD / Schematic · 21YN
What it represents
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.
How to read it
- Identify the residual voltage and residual current measurements and neutral-earthing method.
- Trace the earth-fault operating element and selected feeder trip.
Information to show or reference
- 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.
A distinction that matters
ABB documents 21YN for EFPADM; this admittance earth-fault function is distinct from a generic line-distance zone.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Relion 620 series: published protection function and designation mappings
Public primary-source function or application mapping used to identify this designation; wording and drafting notes are original.
IEEE C37.2-2022: power-system device function numbers
Device-number and suffix convention. This page is not a reproduction of the full licensed standard.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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