27
Undervoltage
A function responding to voltage below its configured operating criteria.
Protection functions
Protection functions · 27Q
Reactive-power undervoltage protection
Combines a reactive-power criterion with undervoltage supervision in the cited interconnection application.
SLD / Schematic · 27Q
What it represents
Combines a reactive-power criterion with undervoltage supervision in the cited interconnection application.
The drafting record should connect this function to the voltage and current inputs and defined reactive-power direction, then trace the combined reactive-power and undervoltage operating logic. 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 voltage and current inputs and defined reactive-power direction.
- Trace the combined reactive-power and undervoltage operating logic.
Information to show or reference
- Label the voltage and current inputs and defined reactive-power direction.
- Cross-reference the combined reactive-power and undervoltage operating logic.
- Retain the complete suffix, selected device tag and manufacturer manual revision.
A distinction that matters
27Q is an Eaton application designation; ABB separately labels a related function 32Q,27, so retain the device-specific legend.
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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