Bus
Busbar
A common conductive connection distributing power to connected circuits.
SLD / Schematic
Functional block · SSI
Source-availability selection interface
Functional block · Switchgear
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
Compares the declared health of available incoming sources for transfer logic.
A simple example
In a switchgear lineup with two incomers and a bus tie, the single-line arrangement helps the engineer identify normal supply paths and which loads change source during a transfer. For this reference, the drawing identifies “Incoming source health” at the input and “Available-source selection” at the output. Source voltage alone may not establish supply suitability.
What the drawings help you do
Start at the named input: Incoming source health. Identify its source device or document and the state represented on the drawing. Follow the named output: Available-source selection. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Input
- Incoming source health
- Output
- Available-source selection
- Application reference
- An explanation of a named drawing function or circuit relationship; the project documents define the equipment and its connections.
Read the source: SEL-451 protection, automation and bay control
Schematic · SSI
What it represents
Compares the declared health of available incoming sources for transfer logic. A source and bus arrangement shows how incoming supplies and outgoing circuits can be connected. Breaker and tie positions determine which sections are energized and whether sources can become electrically paralleled.
In a switchgear lineup with two incomers and a bus tie, the single-line arrangement helps the engineer identify normal supply paths and which loads change source during a transfer. For this reference, the drawing identifies “Incoming source health” at the input and “Available-source selection” at the output. Source voltage alone may not establish supply suitability.
Keep normal positions, transfer limits, source independence and protection-zone boundaries visible. An arrangement drawing explains connectivity; the permitted switching sequence needs a separate approved scheme. 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: Incoming source health. Identify its source device or document and the state represented on the drawing.
- Follow the named output: Available-source selection. Cross-reference its destination and separate the command from confirmation that the equipment responded.
- Source voltage alone may not establish supply suitability.
- Keep normal positions, transfer limits, source independence and protection-zone boundaries visible. An arrangement drawing explains connectivity; the permitted switching sequence needs a separate approved scheme.
Information to show or reference
- Label the source and connection reference for incoming source health.
- Identify the destination and defined state of available-source selection.
- Record the equipment or control-document revision supporting this functional block.
- Check this application limit in the project design: Source voltage alone may not establish supply suitability.
A distinction that matters
Source voltage alone may not establish supply suitability. 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.
SEL-451 protection, automation and bay control
Public technical context for switchboard source and bus interfaces. Bus arrangements, breaker control and bay-level coordination. 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.
Explore related references
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Automatic transfer switch
A mechanically switched changeover device that automatically moves a load from a failed normal source to an alternate source.
SLD / Schematic
ITI
Incomer transfer-in-progress indication
Reports that the documented source-transfer sequence is active and not yet complete.
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Put the reference into a drawing workflow.
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