Busbar symbol
Also called Bus, Switchboard bus
A busbar is the common conductor in a switchboard that all incomers and feeders connect to. On a one-line it is a heavy horizontal line with its voltage and rating.
What the busbar symbol means
A busbar is the common conductor in a switchboard that all incomers and feeders connect to. On a one-line it is a heavy horizontal line with its voltage and rating.
ANSI and IEC symbols
Where you see it
Every switchboard and switchgear line-up, split into sections by bus tie breakers.
What is written next to it
On a one-line, the busbar carries its tag and its ratings: voltage, rated current and short-circuit withstand in kA for 1 or 3 seconds.
What gets checked at commissioning
Before the busbar is energised, the test records usually cover: insulation resistance, joint torque or contact resistance, and phasing. Each check is recorded against the tag, so the system can be handed over with its evidence. See commissioning software.
ANSI device numbers
Protective functions you will often find with a busbar:
- 87B bus differential
See the full list of ANSI device numbers with their IEC equivalents.
Related symbols
Frequently asked questions
What does the busbar symbol look like?
On ANSI drawings: A heavy line, with the feeders dropping from it. In IEC 60617: Drawn the same way.
Is the busbar symbol the same in IEC and ANSI?
Yes, it is drawn the same way in most legends.
Where is a busbar used?
Every switchboard and switchgear line-up, split into sections by bus tie breakers.
Which ANSI device numbers go with a busbar?
87B bus differential.
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