87
Differential protection
A function comparing documented electrical quantities across a protection zone.
Protection functions
Protection functions · 87GD
Restricted ground differential protection
Compares ground-fault-related currents for the restricted zone defined by the cited relay application.
SLD / Schematic · 87GD
What it represents
Compares ground-fault-related currents for the restricted zone defined by the cited relay application.
The drafting record should connect this function to the phase and neutral CT arrangement and winding earthing point, then trace the restricted ground differential zone and trip outputs. 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.
How to read it
- Identify the phase and neutral CT arrangement and winding earthing point.
- Trace the restricted ground differential zone and trip outputs.
Information to show or reference
- Label the phase and neutral CT arrangement and winding earthing point.
- Cross-reference the restricted ground differential zone and trip outputs.
- Retain the complete suffix, selected device tag and manufacturer manual revision.
A distinction that matters
Restricted ground differential protects a defined earthed zone; it is distinct from the transformer-wide phase differential element.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
ETR-4000 and ETR-5000 transformer protection function tables
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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