Circuit breaker symbol
Also called CB, Breaker, Device 52
A circuit breaker opens and closes the circuit and interrupts fault current, tripped by its protective relays or its own trip unit. It is the main switching device on a one-line.
What the circuit breaker symbol means
A circuit breaker opens and closes the circuit and interrupts fault current, tripped by its protective relays or its own trip unit. It is the main switching device on a one-line.
ANSI and IEC symbols
A square in the line, often marked 52, the ANSI device number for an AC circuit breaker.
ANSI SVGWhere you see it
Incomers, bus ties and feeders in medium and low voltage switchgear.
What is written next to it
On a one-line, the circuit breaker carries its tag and its ratings: rated voltage, rated current, short-circuit breaking current in kA and the operating mechanism.
What gets checked at commissioning
Before the circuit breaker is energised, the test records usually cover: insulation resistance, contact resistance, timing, close and trip from local and remote, and interlocks. 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 circuit breaker:
- 52 AC circuit breaker
- 50/51 overcurrent
- 86 lockout
See the full list of ANSI device numbers with their IEC equivalents.
Related symbols
Frequently asked questions
What does the circuit breaker symbol look like?
On ANSI drawings: A square in the line, often marked 52, the ANSI device number for an AC circuit breaker. In IEC 60617: A switch with a cross at the fixed contact. The cross is the circuit breaker function, S00219.
Is the circuit breaker symbol the same in IEC and ANSI?
No. A switch with a cross at the fixed contact. The cross is the circuit breaker function, S00219. The IEC 60617 number is S00287.
Where is a circuit breaker used?
Incomers, bus ties and feeders in medium and low voltage switchgear.
Which ANSI device numbers go with a circuit breaker?
52 AC circuit breaker, 50/51 overcurrent, 86 lockout.
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