Warning over electrical hazard from neutral conductors
Tuesday 21 September, 2010
WorkCover NSW recently issued a safety alert following a serious incident in which an electrician sustained an electric shock after cutting into an isolated power circuit cable that became energised via a neutral backfeed on an electrical installation.
Although the power circuit being worked on had been correctly identified and isolated at the distribution board, inadequate testing of the power circuit, by relying solely on the use of a voltage proximity tester (commonly known as a “volt stick”) contributed to the incident.
Furthermore, failure to undertake a positive test and verify the absence of voltage on the conductors, by using an alternative test instrument such as a multimeter, as well as
the rise in potential to 230 volts of the neutral conductor, once it had been cut by the electrician, also contributed.
To avoid similar incidents, WorkCover NSW said in its safety alert that electrical workers should conduct a site-specific risk assessment and identify the risks associated with the work (including voltages on disconnected neutrals).
Electrical workers should also identify the circuits and apparatus to be worked on, and the appropriate sources of power supply, de-energise the circuits and apparatus, and isolate from all sources of supply, and ensure the supply remains isolated, by locking off and/or tagging the isolator.
“Test before you touch – prove and verify the supply is de-energised by using appropriate test methods and approved test instruments, to test for the absence of voltage on all conductors, including the neutral conductor,” WorkCover NSW said in the safety alert.
Volt sticks, however, should only be used as an indicator and should not be relied on to verify if a circuit is energised or de-energised.
Furthermore, the safety alert noted that electrical workers should use appropriate clothing and personal protective equipment, and ensure that work does not present a hazard to others at the workplace when leaving unfinished work.