CT
Current transformer
A current-measurement transformer used with metering and protection equipment.
SLD / Schematic
Symbols · CT/VT
Combined instrument transformer
Single unit housing a current transformer and voltage transformer for each phase, typical of MV and HV metering points.
In plain English
What does Combined instrument transformer mean?
A combined instrument transformer places a CT and a VT in one insulated housing for each phase. It saves space and foundations at outdoor higher-voltage metering points and appears in MV metering units where the supply authority needs both current and voltage for a billing meter.
A simple example
On a single-line diagram the CT and VT symbols are drawn together with a boundary showing they share one housing. The boundary does not change ratios or classes, which are still stated separately for the current and voltage parts.
What the drawings help you do
Read the CT and VT ratings separately. Check sealing and access requirements for revenue metering. A combined instrument transformer houses a CT and VT together; separate units are drawn and specified independently.
This particular reference
Single unit housing a current transformer and voltage transformer for each phase, typical of MV and higher-voltage metering points. A combined instrument transformer houses a CT and VT together; separate units are drawn and specified independently.
- Winding
- A coil of conductor inside an electrical machine or transformer.
- Phase
- One of the related AC waveforms in a power system.
- Rating
- A value stating the conditions for which equipment is specified.
Read the source: Indoor current and voltage transformers · CPB capacitor voltage transformer
SLD / Schematic · CT/VT
What it represents
A combined instrument transformer places a CT and a VT in one insulated housing for each phase. It saves space and foundations at outdoor HV metering points and appears in MV metering units where the supply authority needs both current and voltage for a billing meter.
On a single-line diagram the CT and VT symbols are drawn together with a boundary showing they share one housing. The boundary does not change ratios or classes, which are still stated separately for the current and voltage parts.
How to read it
- Read the CT and VT ratings separately.
- Check sealing and access requirements for revenue metering.
Information to show or reference
- State CT ratio and class
- State VT ratio and class
- Show sealing or metering boundary
A distinction that matters
A combined instrument transformer houses a CT and VT together; separate units are drawn and specified independently.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Indoor current and voltage transformers
Public manufacturer overview of indoor current and voltage instrument transformers.
CPB capacitor voltage transformer
Public instrument transformer product family context.
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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