CT
Current transformer
A current-measurement transformer used with metering and protection equipment.
SLD / Schematic
Symbols · CBCT
Core-balance current transformer
A core-balance CT measures residual current from the net magnetic effect of conductors passing through its window.
SLD / Schematic · CBCT
What it represents
A core-balance CT measures residual current from the net magnetic effect of conductors passing through its window. It is used with earth-fault protection where the conductor arrangement and sheath routing affect the measurement.
How to read it
- Verify the included conductors and cable-sheath treatment against the protection scheme.
- The preview is an original explanation of this function. Match the actual drawing convention to its legend and the selected equipment documentation.
Information to show or reference
- Identify enclosed conductors
- Show polarity and relay input
- Reference sheath-earthing detail
A distinction that matters
A CBCT measures a combined residual quantity; a phase CT measures an individual conductor current.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Current transformer symbol variants
Public documentation of this equipment function or named vendor variant; the illustration is independently authored and is not the source graphic.
Indoor current and voltage transformers
Public documentation of this equipment function or named vendor variant; the illustration is independently authored and is not the source graphic.
Residual current and neutral-earthing protection context
Public documentation of this equipment function or named vendor variant; the illustration is independently authored and is not the source graphic.
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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