# Auxiliary-input overvoltage

Canonical URL: https://eloragrid.ai/protection-functions/59a-auxiliary-input-overvoltage
Publisher: Elora Grid
Updated: 2026-10-13
Lookup label: 59A
Drawing use: SLD, Schematic
Reference families: IEEE / ANSI, Manufacturer

Supervises high voltage on the auxiliary measurement input in the cited Eaton family.

## What it represents

Supervises high voltage on the auxiliary measurement input in the cited Eaton family.
The drafting record should connect this function to the auxiliary voltage input and the electrical node it measures, then trace the auxiliary overvoltage trip or control output. 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 auxiliary voltage input and the electrical node it measures.
- Trace the auxiliary overvoltage trip or control output.

## Information to show or reference

- Label the auxiliary voltage input and the electrical node it measures.
- Cross-reference the auxiliary overvoltage trip or control output.
- Retain the complete suffix, selected device tag and manufacturer manual revision.

## Important distinction

Auxiliary-input A distinguishes the input circuit here; it does not universally indicate an alarm-only function.

## Facts

- Function designation: 59A
- Base function: 59 — Overvoltage
- 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.