Verification of the absence of operating voltage shall always be completed prior to commencement of work using the intended and reliable equipment.
The absence of operating voltage shall be verified on all phases or poles of the electrical installation at or as near as practicable to the work location.
Voltage detectors and separately applied voltage detecting systems shall be proved immediately before and where possible after use (Test – Measure – Test).
Note that the installation can be energized with a lower voltage than the voltage detector can detect. Therefore, the installation can still be energized even though the voltage detector indicates that the installation is de-energized.
In the case of cable connected electrical installations, if cables that have been isolated cannot be positively identified at the work location, other means of ensuring safety shall be adopted. This may include the use of suitable cable cutting or piercing devices.
If, at any time, the work is interrupted or the work group has to leave the work location and as a consequence cannot continuously control the electrical installation, absence of voltage shall be verified once again prior to recommencement of the work, however if the work location is still earthed and short-circuited verification is not required.