CT
Current transformer
A current-measurement transformer used with metering and protection equipment.
SLD / Schematic
Symbols · VT / PT
Voltage transformer
A transformer providing a voltage signal for metering or protection.
SLD / Schematic · VT / PT
What it represents
A voltage transformer provides a secondary voltage related to the voltage on its primary winding. VT and PT, for potential transformer, are common terms encountered in power drawings. Its representation identifies a measurement function; winding connections, fuses, earthing and secondary circuits need their own documented detail.
A single line diagram places the VT at the system connection being measured. The associated schematic shows how that voltage reaches a meter, relay or control system. A power transformer can look similar in a simplified drawing, so the label and context matter.
How to read it
- Check the measured voltage connection and the number of windings or secondaries shown.
- Read polarity, ratio and secondary earthing from the specified device documentation.
Information to show or reference
- Identify the measured bus or feeder.
- Record the specified ratio and accuracy information.
- Cross-reference primary and secondary protection and terminals.
A distinction that matters
A VT supplies a voltage measurement; a power transformer supplies a power circuit. A shared transformer-like outline does not make their functions interchangeable.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Power, potential and autotransformer symbols
Public potential- and voltage-transformer categories.
Indoor current and voltage transformers
Manufacturer instrument-transformer information.
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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Power transformer
Equipment transferring electrical power between winding circuits.
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Overvoltage
A function responding to voltage above its configured operating criteria.
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