During safe isolation what does zero voltage verification involve?

• A. Verifying that isolated the circuit carries no dangerous voltage by audible indication.
• B. Measuring earth continuity.
• C. Zero voltage confirmation using a calibrated tester on the isolated circuit.
• D. Measuring insulation resistance.

Answer: (C)

Zero voltage verification means confirming that the isolated circuit has no dangerous voltage by measuring with a calibrated tester on the isolated conductors. After you isolate a circuit, you must prove it is dead before touching it, and this is done with a proper, calibrated voltage tester applied to the conductors of the isolated circuit. Relying on an audible indication alone isn’t reliable, because it may not detect all forms of voltage (including phantom or residual voltage).

The other tests have different purposes: measuring earth continuity checks the integrity of the protective earth path, not whether the circuit is de-energized; measuring insulation resistance tests how well the insulation isolates conductors from each other and from earth, which is about insulation health rather than proving absence of voltage on the circuit. So the correct approach is to perform zero voltage confirmation using a calibrated tester on the isolated circuit.