EGT Safety Alert 73 - Electric Shock (Neutral Conductor Back Feed)

Safety Alert
73 – Electric Shock (Neutral Conductor Back Feed)

Date 
11 May 2018

Description
An EGT apprentice was tasked with removing existing lighting fuses/holders and installing a din rail in its place for RCD installation. Both the tradesman and the apprentice proved that both lighting and protected power was isolated – both the tradesman and the apprentice fitted lock-out tags. The apprentice was then given the go ahead to commence the task.

Following this, the apprentice removed the neutrals from the neutral bar. He touched the B2 neutral conductor with his right hand while his left forearm was leaning / touching the earth (switch board) frame - he then received an electric shock.

The apprentice immediately tested and found 266V between the B2 neutral conductor and neutral bar.

Root Cause
Both the tradesman and the apprentice failed to ensure that the last step of the EGT IITT process was physically completed. (Note: The IITT checklist was completed - admin only).

This procedure clearly states to "Re-test separated conductors for possible back feed" as indicated in Figure 1.

Recommendations

• EGT apprentices are to ensure the “test before you touch” principles are physically carried out, including re-testing separated neutral conductors for possible back feed prior to commencement of all work activities.
• EGT host employers must ensure they have this step in their own processes that is adhered to or, failing that, adhere to and administer the EGT Test Before You Touch Isolation Checklist (IITT).
  

Contributing Factors

• Inadequate leadership/supervision – the tradesman failed to ensure that the last step of the EGT IITT process was physically carried out.
  
• Incorrect wiring from one zone to another - it needs to be noted that the source of the supply would have been very difficult to identify as no indication was present. It was only through further investigation by the site tradesman that it was established that B2 was being back fed by DB4. This is a contributing factor to the electric shock.
  

Feedback
For further information regarding this Safety Alert, please contact EGT on (08) 6241 6100.