The operating position of a mechanical switching device that completes an electrical circuit. When a breaker or isolator is closed, power can flow freely through it. This terminology often confuses laypeople who associate a closed state with a blocked pipe or shut door, but in electrical switching, closing the gap means turning the power on.
Confirm the earth switch is open before you order the main feeder breaker closed.
Always double-check terminology with non-electrical staff, as telling them a circuit is closed might make them think it is turned off and safe to touch.
Do not mix it up with
- Dead: A closed circuit is live and conducting, whereas a closed door blocks access; laypeople often confuse closed with dead or off.
Related terms
Circuit
A complete, closed path through which electric current can flow.
Circuit breaker
A mechanical switching device capable of making, carrying and breaking currents under normal and fault conditions.
Dead bus
Busbar with no voltage on it, the condition that lets a breaker close without synchronising checks.