Proving dead is the test-before-touch routine: check the detector on a known live source or proving unit, test every conductor against every other and against earth at the point of work, then check the detector again. Only after that sequence may the equipment be called dead and earthed. Skipping the second check is the classic way to be fooled by an instrument that failed halfway through.
Prove dead at the terminal box, not at the switch, the drawings for this plant have lied to us before.
The three-step sequence is often called live-dead-live.
Also heard as
- test before touch
- live-dead-live
- verify absence of voltage
Related terms
Dead
Isolated from every source, proven free of voltage and safe to work on.
Permit to work
Formal written authority to work on equipment that has been isolated, earthed and declared safe.
Portable earths
Removable earthing leads clamped onto isolated conductors to short them together and to earth during work.