49
Thermal protection
A thermal protection function for a documented machine or transformer application.
Protection functions
Protection functions · 46
Current unbalance / negative sequence
A current phase-balance or reverse-phase function used in documented protection applications.
SLD / Schematic · 46
What it represents
Device function number 46 is associated with reverse-phase or phase-balance current protection. Manufacturer implementations often use negative-sequence or current-unbalance quantities. The implementation, measurement basis and protected equipment must be identified in the protection documentation.
On a power drawing, keep this function reference connected to the selected equipment and its complete designation. A multifunction relay can implement several numbered functions. This entry explains the reference; it supplies no settings or commissioning procedure.
How to read it
- Identify the phase-current measurements used by the device.
- Confirm the manufacturer name and implementation rather than relying only on the number.
Information to show or reference
- Reference phase-current inputs.
- Identify the protected machine or circuit.
- Link the selected relay function documentation.
A distinction that matters
Current unbalance and voltage phase-sequence or balance functions use different measured quantities. Identify the element explicitly.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Public reference table of ANSI device-function numbers
Public manufacturer table used to check the base function-number name.
IEEE C37.2-2022: power-system device function numbers
Normative publication reference for the device-function convention.
Relion 620: functions, codes and symbols
Public examples of manufacturer-specific function names and suffixes.
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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