VT / PT
Voltage transformer
A transformer providing a voltage signal for metering or protection.
SLD / Schematic
Functional block · VVDA
VT voltage-selection discrepancy alarm
Functional block · Substations
An independently authored application reference. The drawing shows the named function or circuit relationship; use the project legend and selected equipment documentation for its drafting form and connections.
Browse this installation focusIn plain English
What this block does
Reports disagreement between the requested voltage reference and its selection feedback.
A simple example
In a substation bay, one voltage circuit can feed protection while a separately identified winding supplies metering. A voltage-selection circuit must make clear which bus or line measurement is being used. For this reference, the drawing identifies “Selection command and feedback” at the input and “Voltage selection fault” at the output. The affected protection and control functions need identification.
What the drawings help you do
Start at the named input: Selection command and feedback. Identify its source device or document and the state represented on the drawing. Follow the named output: Voltage selection fault. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Selection command and feedback
- Output
- Voltage selection fault
- Application reference
- An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.
Read the source: Indoor current and voltage transformers
Schematic · VVDA
What it represents
Reports disagreement between the requested voltage reference and its selection feedback. A voltage-transformer secondary arrangement connects a defined primary voltage measurement to protection, metering or control inputs. Winding identity, fuse protection and the voltage reference must remain visible across the drawing.
In a substation bay, one voltage circuit can feed protection while a separately identified winding supplies metering. A voltage-selection circuit must make clear which bus or line measurement is being used. For this reference, the drawing identifies “Selection command and feedback” at the input and “Voltage selection fault” at the output. The affected protection and control functions need identification.
Show the primary measurement point, secondary connection, protective devices and relay reference. A missing measurement can resemble a real system disturbance unless the voltage-circuit health is supervised appropriately. The functional block is an independent explanation of this named application. Equipment-specific ratings, terminal connections and operating conditions must be established in the project documentation.
How to read it
- Start at the named input: Selection command and feedback. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Voltage selection fault. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- The affected protection and control functions need identification.
- Show the primary measurement point, secondary connection, protective devices and relay reference. A missing measurement can resemble a real system disturbance unless the voltage-circuit health is supervised appropriately.
Information to show or reference
- Label the source and connection reference for selection command and feedback.
- Identify the destination and defined state of voltage selection fault.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: The affected protection and control functions need identification.
A distinction that matters
The affected protection and control functions need identification. This reference describes the named application; it does not establish a new IEC graphical symbol, an ANSI device-function number or an exact manufacturer connection diagram.
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 technical context for voltage-transformer secondary arrangements. Current and voltage measurement transformers and their secondary interfaces. The application text and educational graphic are independently authored; the publisher does not certify this representation.
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. Original artwork is available under CC BY 4.0. Third-party references retain their own terms.
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