Dead in electrical safety means more than switched off: the equipment has been isolated from every possible source, tested with an approved detector that is itself proven before and after, and usually earthed. Insiders treat the word as a claim backed by a test, so 'it should be dead' is not accepted on site. A dead busbar or cable can still hold capacitive charge or be backfed, which is why proving and earthing follow isolation.
Feeder's isolated both ends and proven dead at the work site, earths are on, you can open the joint bay.
Also heard as
- de-energised
- de-energized
- cold
Related terms
Live
Connected to a source of voltage, or describing a conductor meant to be energised in normal use.
Prove dead
To test isolated equipment with a verified voltage detector and confirm no voltage before anyone touches it.
Portable earths
Removable earthing leads clamped onto isolated conductors to short them together and to earth during work.
Dead bus
Busbar with no voltage on it, the condition that lets a breaker close without synchronising checks.