# Restrained current differential protection

Canonical URL: https://eloragrid.ai/protection-functions/87r-restrained-current-differential-protection
Publisher: Elora Grid
Updated: 2026-10-13
Lookup label: 87R
Drawing use: SLD, Schematic
Reference families: IEEE / ANSI, Manufacturer

Uses a differential operating quantity with restraint in the cited transformer-relay application.

## What it represents

Uses a differential operating quantity with restraint in the cited transformer-relay application.
The drafting record should connect this function to the differential-zone CT inputs and restraint-measurement definitions, then trace the restrained element and transformer trip matrix. 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 differential-zone CT inputs and restraint-measurement definitions.
- Trace the restrained element and transformer trip matrix.

## Information to show or reference

- Label the differential-zone CT inputs and restraint-measurement definitions.
- Cross-reference the restrained element and transformer trip matrix.
- Retain the complete suffix, selected device tag and manufacturer manual revision.

## Important distinction

Eaton's 87R mapping is restrained differential; R here does not mean the calculated residual-current input used in 50R.

## Facts

- Function designation: 87R
- Base function: 87 — Differential protection
- Published mapping: Eaton ETR family
- Suffix scope: Application or manufacturer specific; check the complete drawing legend and selected device manual.

## Public references

- [ETR-4000 and ETR-5000 transformer protection function tables](https://www.eaton.com/us/en-us/catalog/electrical-circuit-protection/transformer-relays.html) — Eaton. 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](https://ieeexplore.ieee.org/document/9984140) — IEEE. Device-number and suffix convention. This page is not a reproduction of the full licensed standard.

## 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.