51
Time overcurrent
An overcurrent function with a documented time characteristic.
Protection functions
Protection functions · 51P
Time phase-overcurrent protection
Supervises phase overcurrent using the selected time-current characteristic or intentional operating delay.
SLD / Schematic · 51P
What it represents
Supervises phase overcurrent using the selected time-current characteristic or intentional operating delay.
The drafting record should connect this function to the phase CT inputs and coordination-study reference, then trace the phase time-overcurrent output and protected breaker. 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 CT inputs and coordination-study reference.
- Trace the phase time-overcurrent output and protected breaker.
Information to show or reference
- Label the phase CT inputs and coordination-study reference.
- Cross-reference the phase time-overcurrent output and protected breaker.
- Retain the complete suffix, selected device tag and manufacturer manual revision.
A distinction that matters
51P identifies phase overcurrent timing; the symbol alone does not choose an IEC or IEEE curve family.
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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