87
Differential protection
A function comparing documented electrical quantities across a protection zone.
Protection functions
Protection functions · 87G
Generator differential protection
Compares current measurements bounding the selected generator differential zone.
SLD / Schematic · 87G
What it represents
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.
How to read it
- Identify the generator terminal and neutral-side CT connections.
- Trace the generator differential zone and unit tripping matrix.
Information to show or reference
- 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.
A distinction that matters
G denotes generator in this differential application; it should not be interpreted using the ground-current meaning of 50G.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
ANSI device-number and suffix reference table
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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