LPCT
Low-power current transformer
Small iron-core CT with an integral shunt that delivers a low-level voltage signal instead of a standard secondary current.
SLD / Schematic
Symbols · RC
Rogowski coil current sensor
Air-cored coil around a conductor whose output voltage is proportional to the rate of change of current.
In plain English
What does Rogowski coil current sensor mean?
A Rogowski coil is wound on a non-magnetic former and placed around the conductor. Its output voltage is proportional to the rate of change of current, so an integrator in the relay or meter reconstructs the current waveform. With no iron core it does not saturate, which suits high fault currents and wide measuring ranges.
A simple example
The output is a low-level voltage, not a current, so it must go to an input designed for it and cannot be wired into a conventional 1 A or 5 A CT circuit. The symbol does not show the sensor's coefficient, cable length limits or the matching relay input, all of which affect accuracy.
What the drawings help you do
Confirm the receiving input is designed for Rogowski sensors. Do not apply CT shorting practice to this low-level voltage output. A Rogowski coil has no iron core and gives a voltage output; a conventional CT has an iron core and a current output.
This particular reference
Air-cored coil around a conductor whose output voltage is proportional to the rate of change of current. A Rogowski coil has no iron core and gives a voltage output; a conventional CT has an iron core and a current output.
- Normally open / normally closed
- The contact state in the normal condition defined for the drawing.
- Coil
- A wound conductor that can produce a magnetic field when energised.
- Terminal
- An identified point where a conductor connects.
Read the source: Medium-voltage indoor sensors: Rogowski coil and voltage divider low-power instrument transformers · Indoor current and voltage transformers
SLD / Schematic · RC
What it represents
A Rogowski coil is wound on a non-magnetic former and placed around the conductor. Its output voltage is proportional to the rate of change of current, so an integrator in the relay or meter reconstructs the current waveform. With no iron core it does not saturate, which suits high fault currents and wide measuring ranges.
The output is a low-level voltage, not a current, so it must go to an input designed for it and cannot be wired into a conventional 1 A or 5 A CT circuit. The symbol does not show the sensor's coefficient, cable length limits or the matching relay input, all of which affect accuracy.
How to read it
- Confirm the receiving input is designed for Rogowski sensors.
- Do not apply CT shorting practice to this low-level voltage output.
Information to show or reference
- State sensor coefficient
- Reference matching input
- Respect cable length limit
A distinction that matters
A Rogowski coil has no iron core and gives a voltage output; a conventional CT has an iron core and a current output.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Medium-voltage indoor sensors: Rogowski coil and voltage divider low-power instrument transformers
Public manufacturer page describing low-power instrument transformers based on Rogowski coils and voltage dividers.
Indoor current and voltage transformers
Public manufacturer overview of indoor current and voltage instrument transformers.
About this graphic
This illustration was authored independently by Elora Grid to explain the concept. It is not reproduced from a customer drawing, an official standard graphic or a manufacturer CAD file. Its correspondence to an exact IEC or IEEE symbol identifier has not been certified.
SVG and DXF downloads contain this original artwork. DXF uses unscaled drawing units; a GA envelope supplies no product dimensions, clearances or fabrication information. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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