# Numerical protection relay (IED)

Canonical URL: https://eloragrid.ai/symbols/numerical-protection-relay
Publisher: Elora Grid
Updated: 2026-10-28
Lookup label: IED
Drawing use: SLD, Schematic
Reference families: IEC, Manufacturer

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.

### Terms

- 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.

Concept diagram: Identify the device and form → Read the connections and state → Check the equipment reference
A guide to reading this reference. The original symbol illustration and its drawing notes appear below; these boxes are not a wiring diagram.

- [Relion 620: functions, codes and symbols](https://techdoc.relays.protection-control.abb/r/620-series-IEC-60870-5-103-Point-List-Manual/2.0-FP1-IEC/en-US/Functions-codes-and-symbols)
- [SEL 2022 Product and Solution Guide: published protection function tables](https://selinc.com/api/download/136012)


## 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

## Important distinction

An IED block represents a multifunction device; a single measuring relay symbol represents one function.

## Facts

- Content: Protection, control and measuring functions in one device
- Function labels: IEC symbols or ANSI device numbers
- Preview: Functional illustration of the device role; not a product footprint or certified standard graphic

## Public references

- [Relion 620: functions, codes and symbols](https://techdoc.relays.protection-control.abb/r/620-series-IEC-60870-5-103-Point-List-Manual/2.0-FP1-IEC/en-US/Functions-codes-and-symbols) — ABB. Public manufacturer list of relay functions with codes and symbols.
- [SEL 2022 Product and Solution Guide: published protection function tables](https://selinc.com/api/download/136012) — Schweitzer Engineering Laboratories. Public relay product guide with function tables.

## Graphic scope

Independent original educational concept illustration by Elora Grid. Not a certified standards graphic or manufacturer footprint. Unitless; not to scale. Original artwork licence: https://creativecommons.org/licenses/by/4.0/. Publisher material is linked only.