# Maximum-voltage measuring relay

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

Measuring relay that operates when the monitored voltage rises above its set level.

## In plain English

### What does Maximum-voltage measuring relay mean?

The maximum-voltage relay form operates when voltage exceeds its setting. Typical uses include generator overvoltage after load rejection, capacitor bank protection and inverter connection points, where sustained high voltage can stress insulation or breach grid connection limits.

### A simple example

The box shows a greater-than voltage threshold but not whether the element uses phase-to-phase or phase-to-neutral quantities, the reset ratio or the time delay. Grid-connection settings are usually specified as several stages with different delays, which this single symbol does not reveal.

### What the drawings help you do

Identify the voltage connection used by the element. Check for multiple stages in the settings record. A maximum-voltage relay responds to high voltage magnitude; a residual voltage relay responds to neutral displacement.

### This particular reference

Measuring relay that operates when the monitored voltage rises above its set level. A maximum-voltage relay responds to high voltage magnitude; a residual voltage relay responds to neutral displacement.

### Terms

- Coil: A wound conductor that can produce a magnetic field when energised.
- Phase: One of the related AC waveforms in a power system.
- Terminal: An identified point where a conductor connects.

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.

- [AutoCAD Electrical: Voltage monitoring relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-5296749E-9336-4B07-9956-160963D6C848.htm)
- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/)


## What it represents

The maximum-voltage relay form operates when voltage exceeds its setting. Typical uses include generator overvoltage after load rejection, capacitor bank protection and inverter connection points, where sustained high voltage can stress insulation or breach grid connection limits.
The box shows a greater-than voltage threshold but not whether the element uses phase-to-phase or phase-to-neutral quantities, the reset ratio or the time delay. Grid-connection settings are usually specified as several stages with different delays, which this single symbol does not reveal.

## How to read it

- Identify the voltage connection used by the element.
- Check for multiple stages in the settings record.

## Information to show or reference

- State threshold and delay
- Show VT connection
- Reference stage settings

## Important distinction

A maximum-voltage relay responds to high voltage magnitude; a residual voltage relay responds to neutral displacement.

## Facts

- Measured quantity: Voltage above a set level
- Publisher reference token: HCR1F36 (Autodesk identifier; not an IEC database ID)
- Preview: Independent educational concept; consult the publisher and applicable standard for the exact graphic

## 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 AutoCAD Electrical relay listing that names the Maximum Voltage Protection block; the illustration is independently drawn.
- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/) — IEC. IEC context for graphical symbols used in diagrams; no IEC graphic is reproduced.

## 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.