# Neutral-current measuring relay

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

Measuring relay fed from a CT in a neutral conductor or star-point connection, responding to neutral current.

## In plain English

### What does Neutral-current measuring relay mean?

This relay form is used where a CT is installed in a neutral conductor or in the earthing connection of a transformer or generator star point. Current there indicates earth faults or, in four-wire systems, heavy unbalance and triplen harmonic loading, depending on where the CT sits.

### A simple example

The symbol identifies the measured conductor but not the purpose. A neutral CT in the star-point earth lead gives standby earth-fault protection, while one in the four-wire neutral of a feeder sees load unbalance as well, so settings and grading differ greatly.

### What the drawings help you do

Confirm whether the CT is in the neutral conductor or the earthing lead. Check grading against downstream earth-fault devices. A neutral-current relay measures one neutral path; a residual connection sums the three phase CTs to derive the same quantity.

### This particular reference

Measuring relay fed from a CT in a neutral conductor or star-point connection, responding to neutral current. A neutral-current relay measures one neutral path; a residual connection sums the three phase CTs to derive the same quantity.

### Terms

- Winding: A coil of conductor inside an electrical machine or transformer.
- Coil: A wound conductor that can produce a magnetic field when energised.
- 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: Current monitoring relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-E0DDA638-4664-4F1E-B191-29A4C40C4A0A.htm)
- [IEC graphical symbols for diagrams](https://tc3.iec.ch/tc-activity/graphical-symbols-for-diagrams/)


## What it represents

This relay form is used where a CT is installed in a neutral conductor or in the earthing connection of a transformer or generator star point. Current there indicates earth faults or, in four-wire systems, heavy unbalance and triplen harmonic loading, depending on where the CT sits.
The symbol identifies the measured conductor but not the purpose. A neutral CT in the star-point earth lead gives standby earth-fault protection, while one in the four-wire neutral of a feeder sees load unbalance as well, so settings and grading differ greatly.

## How to read it

- Confirm whether the CT is in the neutral conductor or the earthing lead.
- Check grading against downstream earth-fault devices.

## Information to show or reference

- Show neutral CT location
- State setting and delay
- Reference grading study

## Important distinction

A neutral-current relay measures one neutral path; a residual connection sums the three phase CTs to derive the same quantity.

## Facts

- Measured quantity: Current in a neutral or star-point conductor
- Publisher reference token: HCR1F32 (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: Current monitoring relays](https://help.autodesk.com/cloudhelp/2021/ENU/AutoCAD-Electrical/files/GUID-E0DDA638-4664-4F1E-B191-29A4C40C4A0A.htm) — Autodesk. Public AutoCAD Electrical relay listing that names the In Neutral 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.