VT / PT
Voltage transformer
A transformer providing a voltage signal for metering or protection.
SLD / Schematic
Functional block · BSRI
Bus-voltage selection relay interface
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
Selects the voltage measurement associated with the bus supplying the protected circuit.
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 “Bus measurements and selection status” at the input and “Selected bus voltage” at the output. Selection must follow the actual bus configuration.
What the drawings help you do
Start at the named input: Bus measurements and selection status. Identify its source device or document and the state represented on the drawing. Follow the named output: Selected bus voltage. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Bus measurements and selection status
- Output
- Selected bus voltage
- 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 · BSRI
What it represents
Selects the voltage measurement associated with the bus supplying the protected circuit. 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 “Bus measurements and selection status” at the input and “Selected bus voltage” at the output. Selection must follow the actual bus configuration.
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: Bus measurements and selection status. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Selected bus voltage. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Selection must follow the actual bus configuration.
- 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 bus measurements and selection status.
- Identify the destination and defined state of selected bus voltage.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Selection must follow the actual bus configuration.
A distinction that matters
Selection must follow the actual bus configuration. 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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