Which sequence describes the safe isolation procedure before work?

• A. Identify circuit isolate supply apply lock off tag verify zero voltage with a calibrated tester ensure isolation remains in place.
• B. Switch off the circuit and wait for the worker to confirm with no voltage.
• C. Remove the protective device and proceed.
• D. Switch off all MCBs and test with a non contact tester.

Answer: (A)

Safe isolation before work means making sure there is no live energy in the circuit and that it cannot be re-energized while you’re working. The proper sequence is to identify the circuit, isolate the energy source, apply a lockout and tag to the energy‑isolating device, then verify zero energy with a calibrated tester and keep the isolation in place until the job is finished. This combination prevents accidental re-energization and accounts for stored or residual energy that could still pose a danger. Relying on switching off the circuit and hoping there’s no voltage, or removing protection and proceeding, or just using a non-contact tester after switching off MCBs does not guarantee safety, since it can miss actual energy presence, leave the circuit capable of being re-energized, or fail to de-energize stored energy.