Safety Alert 137 | Electric Shock
A first-year apprentice was working on a commercial rooftop completing solar installation
works.
The apprentice started on site and was instructed to terminate MC4 (DC connector)
connections at either end of a DC feed cable that had been prepared the previous day. The
apprentice was working under general supervision, with the supervising tradesperson on the
same roof but n1ot in close proximity.
The apprentice began at the array side of the cable and terminated both the positive and
negative conductors before plugging them into the solar array. This action energised the
cable.
The apprentice then moved to the opposite end of the cable to complete the remaining
terminations. While handling the DC cable prior to termination, the apprentice contacted both
the positive and negative conductors, receiving an electric shock through the finger and
sustaining a minor contact burn.
It was identified that the apprentice was not aware that the cable had become live once
connected to the array and had not been clearly instructed on the risks associated with
constant live DC when working with solar panels. The apprentice was not specifically
instructed to plug in the connectors, however, was also not clearly instructed not to do so.
The apprentice did the right thing and reported the incident to their supervisor immediately,
allowing for the host company and EGT to arrange an ECG straight away. The ECG was
carried out, and the apprentice was cleared of any effects.
The site was made safe following the incident.
Remember your ABC – Assume nothing, Believe no-one, Check everything
Root Cause
- Job/System Factors:
• Inadequate work practice – Cable was energised by connection to the solar array prior to both ends being safely terminated
• Inadequate instruction and supervision – the Apprentice was not clearly instructed on the correct sequence of work or the risks of live DC when working with solar systems - Inadequate work procedures:
• Failure to establish safe work sequence – No clear process in place to prevent energisation of cables during installation
• Failure to identify hazard – Solar DC not recognised as becoming live immediately once connected to the array - Contributing Factors
• Lack of awareness – Apprentice did not understand that connecting to the array would energise the cable.
• Instruction – No clear direction provided on when DC connectors were to be plugged in.
• Sequence of work – Cable was connected and energised before work at the opposite end was complete.
• Supervision – Supervising tradesperson was not in close proximity during a high-risk task i.e. direct supervision.
• Nature of solar work – DC cabling becomes live when the solar panels they are connected to are exposed to light and cannot be isolated in the same manner as typical LV circuits.
Recommendations
- EGT apprentices are to ensure that safe work sequences are followed, with all terminations completed prior to energising any part of a solar system.
- EGT apprentices must ensure that they DO NOT connect DC plugs until the system is ready for energisation and only under the direction of their supervising electrical worker.
- Clearly identify designated DC disconnect points within the array and implement controls (such as taping or blocking connectors) to prevent accidental connection prior to completion of all terminations.
- Ensure adequate instruction and supervision of apprentices undertaking solar installation works.
- Apprentices should always be aware that solar DC cabling can become live immediately once connected and must plan works accordingly.
For further information regarding this Safety Alert, please contact EGT on (08) 6241 6100 or
talk to your Field Officer.
