# Differential-current measuring relay

Canonical URL: https://eloragrid.ai/symbols/differential-current-measuring-relay
Publisher: Elora Grid
Updated: 2026-10-13
Lookup label: I DIFF
Drawing use: SLD, Schematic
Reference families: Manufacturer

A differential-current relay responds to the relationship between specified current inputs.

## What it represents

A differential-current relay responds to the relationship between specified current inputs. The schematic must identify input directions, ratio matching and the protected or monitored zone.

## How to read it

- Follow polarity and reference directions on all compared current circuits.
- The preview is an original explanation of this function. Match the actual drawing convention to its legend and the selected equipment documentation.

## Information to show or reference

- Identify compared inputs
- Show polarity references
- Link setting and zone documentation

## Important distinction

Differential measurement is not simply a single high-current threshold.

## Facts

- Drawing role: Monitoring element
- Representation scope: Functional concept; not an official standard graphic or a product footprint
- Public vendor block reference: HCR1F29, VCR1F29 (Autodesk identifiers; not IEC symbol numbers)
- Identifier status: The short label is a functional lookup label, not an assigned IEC or IEEE symbol number. Any separately listed Autodesk code is a verified vendor block name.

## Public references

- [AutoCAD Electrical: Current monitoring relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-E0DDA638-4664-4F1E-B191-29A4C40C4A0A.htm) — Autodesk. Public documentation of this equipment function or named vendor variant; the illustration is independently authored and is not the source graphic.

## 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.