EGT Safety Alert 80: Electric shock - contact between active and neutral

Date
5 June 2019

Description
The apprentice was tasked with replacing a faulty light fitting in the basement / lower level carpark at the RAAFA Estate Headquarters in South Perth. Isolation was carried out at an incorrect load centre (located in the floor above) by the tradesperson and confirmed by the apprentice via mobile phone that the circuit was identified and isolated as indicated by his voltstick. The apprentice was located at the light fitting on the carpark level.

The tradesperson then went into the basement and tested the light fitting himself. He verified that the circuit was not live. He then instructed the apprentice to climb the fibreglass ladder to disconnect and remove the light fitting. When the apprentice was descending the ladder, his left ear brushed against the bare conductors and he received an electric shock. 

The supply to the light fitting (controlled by a motion sensor) was in fact fed from a switchboard on the same level, approximately 15 metres away from the light fitting.

Root cause

Job / system factors:
-    Inadequate instruction by the tradesperson for not following the correct isolation procedure.

Personal factors:
-    Lack of knowledge – the tradesperson did not make himself aware of the circuit arrangement.

Type of contact:
-    Caught between – contact between active and neutral whilst working on a fibreglass ladder, and
-    Contact with – electricity.

Contributing factors

  • Failure to follow the isolation procedure. (Note: the correct isolation procedure was carried out at the correct load centre on the same level (basement carpark) post incident)
  • The tradesperson accepted the receptionists’ word for the location of the applicable switch board. 
  • When testing we can assume that the motion sensor was not activated, hence the supply at the light fitting was not live - the motion sensor was giving the indication on and off at the light fitting as vehicles entered the carpark.
  • Whilst the tradesperson was turning the light circuit breaker on and off, the apprentices’ voltstick indicated same (indicated same by mobile phone).
  • The apprentice did not participate in the tag and lock out procedure (as per page 18 of Building and Energy's 'Safe working guidelines and assessment for electrical apprentices').

Recommendations

  • Reaffirmation of the isolation procedure.
  • EGT Apprentices are to participate in the verification of de-energisation as per page 18 of the Safe working guidelines and assessment for electrical apprentices (see Figure 1).

Figure 1


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