ATS
Automatic transfer switch
A mechanically switched changeover device that automatically moves a load from a failed normal source to an alternate source.
SLD / Schematic
Symbols · BP/ATS
Bypass-isolation transfer switch
An automatic transfer switch paired with a manual bypass switch so the ATS can be isolated for maintenance without losing the load.
In plain English
What does Bypass-isolation transfer switch mean?
A bypass-isolation transfer switch combines an automatic transfer switch with a parallel manual bypass switch. The bypass can connect the load directly to either source while the automatic switch is withdrawn or isolated, so maintenance and testing can proceed without interrupting critical loads such as hospital or emergency circuits.
A simple example
Single-line diagrams draw the automatic changeover in one path and a manually operated changeover in parallel, with isolating contacts on the automatic unit. Interlocks prevent the bypass from connecting the load to a source different from the one the automatic switch is using at the moment of bypass.
What the drawings help you do
The symbol does not show the interlock sequence or whether the bypass operation is load-break. Operators need the switching procedure to use it safely.
This particular reference
An automatic transfer switch paired with a manual bypass switch so the ATS can be isolated for maintenance without losing the load. A bypass-isolation switch adds a manual path around the ATS; a plain ATS must be not supplied with operating power for maintenance.
- Normally open / normally closed
- The contact state in the normal condition defined for the drawing.
- Rating
- A value stating the conditions for which equipment is specified.
- Schematic
- A drawing showing function and connections rather than physical appearance.
Read the source: Transfer switch fundamentals · Generator switchgear and paralleling controls
SLD · BP/ATS
What it represents
A bypass-isolation transfer switch combines an automatic transfer switch with a parallel manual bypass switch. The bypass can connect the load directly to either source while the automatic switch is withdrawn or isolated, so maintenance and testing can proceed without interrupting critical loads such as hospital or emergency circuits.
Single-line diagrams draw the automatic changeover in one path and a manually operated changeover in parallel, with isolating contacts on the automatic unit. Interlocks prevent the bypass from connecting the load to a source different from the one the automatic switch is using at the moment of bypass.
The symbol does not show the interlock sequence or whether the bypass operation is load-break. Operators need the switching procedure to use it safely.
How to read it
- Identify the isolating contacts that allow the automatic unit to be withdrawn.
- Bypass and automatic paths should be interlocked.
Information to show or reference
- State ratings for both paths.
- Show isolation contacts and interlocks.
- Reference bypass procedure.
A distinction that matters
A bypass-isolation switch adds a manual path around the ATS; a plain ATS must be de-energised for maintenance.
Sources you can follow
These public references support the explanation and provide further detail. Their graphics and downloadable files remain with their publishers.
Transfer switch fundamentals
Public transfer switch fundamentals.
Generator switchgear and paralleling controls
Public generator switchgear 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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