# Low-power current transformer

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

Small iron-core CT with an integral shunt that delivers a low-level voltage signal instead of a standard secondary current.

## In plain English

### What does Low-power current transformer mean?

A low-power CT uses a small magnetic core and an integral burden resistor, so its output is a low-level voltage proportional to primary current. It suits digital relays and compact switchgear, and a single LPCT can often replace several conventional CT ratios.

### A simple example

Because the burden is built in, the output must not be shorted or loaded like a conventional CT, and it cannot feed electromechanical relays or ordinary meters. The symbol shows the sensor but the reader must confirm the relay input type and the sensor's rated output.

### What the drawings help you do

Check the receiving input is an LPCT input. Do not short the output as for a conventional CT. An LPCT has an iron core with integral burden; a Rogowski coil has no iron core and gives a di/dt output.

### This particular reference

Small iron-core CT with an integral shunt that delivers a low-level voltage signal instead of a standard secondary current. An LPCT has an iron core with integral burden; a Rogowski coil has no iron core and gives a di/dt output.

### Terms

- Winding: A coil of conductor inside an electrical machine or transformer.
- Coil: A wound conductor that can produce a magnetic field when energised.
- Signal: Electrical information passed between devices, rather than necessarily the main power supply.

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.

- [Medium-voltage indoor sensors: Rogowski coil and voltage divider low-power instrument transformers](https://www.abb.com/global/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-sensors)
- [Indoor current and voltage transformers](https://www.abb.com/gb/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-instrument-transformers)


## What it represents

A low-power CT uses a small magnetic core and an integral burden resistor, so its output is a low-level voltage proportional to primary current. It suits digital relays and compact switchgear, and a single LPCT can often replace several conventional CT ratios.
Because the burden is built in, the output must not be shorted or loaded like a conventional CT, and it cannot feed electromechanical relays or ordinary meters. The symbol shows the sensor but the reader must confirm the relay input type and the sensor's rated output.

## How to read it

- Check the receiving input is an LPCT input.
- Do not short the output as for a conventional CT.

## Information to show or reference

- State rated output
- Reference relay input type
- Show sensor cable

## Important distinction

An LPCT has an iron core with integral burden; a Rogowski coil has no iron core and gives a di/dt output.

## Facts

- Output: Low-level voltage proportional to current
- Burden: Integral to the sensor
- Preview: Functional illustration of the device role; not a product footprint or certified standard graphic

## Public references

- [Medium-voltage indoor sensors: Rogowski coil and voltage divider low-power instrument transformers](https://www.abb.com/global/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-sensors) — ABB. Public manufacturer page describing low-power instrument transformers based on Rogowski coils and voltage dividers.
- [Indoor current and voltage transformers](https://www.abb.com/gb/en/areas/electrification/medium-voltage/grid-components/core-components/indoor-instrument-transformers) — ABB. Public manufacturer overview of indoor current and voltage instrument transformers.

## 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.