# Loss-of-voltage monitoring relay

Canonical URL: https://eloragrid.ai/symbols/loss-of-voltage-monitoring-relay
Publisher: Elora Grid
Updated: 2026-10-13
Lookup label: U LOSS
Drawing use: SLD, Schematic
Reference families: Manufacturer

A loss-of-voltage relay changes its output for a documented absence-of-voltage condition.

## What it represents

A loss-of-voltage relay changes its output for a documented absence-of-voltage condition. Schematics distinguish measurement failure, actual source loss and auxiliary-supply loss where the design requires them.

## How to read it

- Trace the monitored voltage independently from relay auxiliary power.
- 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 monitored source
- State loss criterion
- Show output and supply-loss behaviour

## Important distinction

Loss-of-voltage indication is not necessarily the same function as breaker undervoltage release.

## Facts

- Drawing role: Monitoring element
- Representation scope: Functional concept; not an official standard graphic or a product footprint
- Public vendor block reference: HCR1F39, VCR1F39 (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: Voltage monitoring relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-5296749E-9336-4B07-9956-160963D6C848.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.