81
Frequency protection
A function responding to a documented frequency condition.
Protection functions
Protection functions · 7
Rate-of-change relay
Responds to how quickly a monitored quantity changes rather than only its absolute magnitude.
SLD / Schematic · 7
What it represents
Responds to how quickly a monitored quantity changes rather than only its absolute magnitude.
In a drafting package, connect this reference to the measured quantity and its engineering units. The associated drawing should trace the rate-sensitive alarm or trip output; the number identifies the role and does not specify the terminal arrangement, ratings or operating settings.
How to read it
- Identify the measured quantity and its engineering units.
- Trace the rate-sensitive alarm or trip output.
Information to show or reference
- Label the measured quantity and its engineering units.
- Cross-reference the rate-sensitive alarm or trip output.
- Identify the device tag, manual revision and logic drawing that define this implementation.
A distinction that matters
Device 7 is a general rate-of-change reference; 81R specifically denotes frequency rate of change in cited relay families.
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 manufacturer number/name association. Drafting explanations are independently written.
IEEE C37.2-2022: power-system device function numbers
Normative device-number publication; exact edition wording and compliance require the 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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