K MEAS
Measuring relay
A measuring relay responds to a measured electrical quantity and issues an output according to its configuration.
Schematic
Symbols · IED
Numerical protection relay (IED)
Single relay block on an SLD that lists the protection functions it provides, with CT, VT and trip connections.
In plain English
What does Numerical protection relay (IED) mean?
A numerical protection relay, or IED, combines many protection, control and measuring functions in one device. Single-line diagrams draw it as a block connected to its CTs, VTs and breaker trip coil, with the enabled functions listed inside or beside it using IEC function symbols or ANSI device numbers.
A simple example
Listing a function on the block shows it is enabled, not how it is set. The block does not show settings, logic between functions, or communications, so it must be read with the settings file and the protection logic diagram.
What the drawings help you do
Read the function list as enabled functions, not settings. Trace CT, VT and trip connections to the block. An IED block represents a multifunction device; a single measuring relay symbol represents one function.
This particular reference
Single relay block on an single-line diagram that lists the protection functions it provides, with CT, VT and trip connections. An IED block represents a multifunction device; a single measuring relay symbol represents one function.
- Coil
- A wound conductor that can produce a magnetic field when energised.
- Signal
- Electrical information passed between devices, rather than necessarily the main power supply.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: Relion 620: functions, codes and symbols · SEL 2022 Product and Solution Guide: published protection function tables
SLD / Schematic · IED
What it represents
A numerical protection relay, or IED, combines many protection, control and measuring functions in one device. Single-line diagrams draw it as a block connected to its CTs, VTs and breaker trip coil, with the enabled functions listed inside or beside it using IEC function symbols or ANSI device numbers.
Listing a function on the block shows it is enabled, not how it is set. The block does not show settings, logic between functions, or communications, so it must be read with the settings file and the protection logic diagram.
How to read it
- Read the function list as enabled functions, not settings.
- Trace CT, VT and trip connections to the block.
Information to show or reference
- List enabled functions
- Show CT, VT and trip connections
- Reference settings file
A distinction that matters
An IED block represents a multifunction device; a single measuring relay symbol represents one function.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Relion 620: functions, codes and symbols
Public manufacturer list of relay functions with codes and symbols.
SEL 2022 Product and Solution Guide: published protection function tables
Public relay product guide with function tables.
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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