On 14 September 2022, an electrical worker received burns to his left arm and flash burns to his eyes from an arc flash explosion that occurred while load testing electrical supply wiring to a new electricity meter. The meter was being added to a main switchboard in a large commercial/residential building under construction.
What is arc flash?
Arc flash is the light and heat produced from an arc fault – created by a short circuit between two conductors; phase to phase or phase to earth. The massive energy released in the fault can rapidly vaporize the metal conductors and tools involved, changing it from a solid state to a gas vapour (plasma) that expands with explosive force (arc blast). The temperature of the plasma can reach 19,000ºC – hotter than the surface of the sun. Exposure to the noise, concussive forces, blasted molten metal, high-energy radiation and temperatures can be catastrophic.
The radiant energy released by an electric arc is capable of permanently injuring or killing people. Arc flashes may cause severe burns to the skin and flash burns to the face and eyes. Inhaled hot gases and molten particles can cause serious internal burns to the throat and lungs. Injury can also occur through the impact from flying debris and dislodged components, or by the concussive blast.
Electricians must not work live on customer’s electrical equipment or installation merely because it is more convenient. Convenience is not an excuse to carry out dangerous work.
The Work Health and Safety Regulations 2012 (SA) prohibit work on energised (live) electrical equipment unless one or more of the exceptions. Refer to the Approved Code of Practice: Managing Electrical Risks in the Workplace for more information on the few circumstances under which working live is permitted and how it should be carried out.
Working de-energised eliminates significant electrical risks. The following are the key steps for an effective isolation of electrical supply.
Consultation: consult with the person who manages or controls the workplace or the premises (eg in relation to the timing of the work) and notify any other affected people as appropriate
- identify the circuit(s) requiring isolation
- disconnect active conductors from the relevant source(s), noting there may be multiple sources and stand-by systems/generators/photovoltaic systems as well as auxiliary supplies from other boards
- if a removable or rack out circuit breaker or combined fuse switch is used, it should be racked out or removed then locked open and danger tagged
- each high-voltage exposed part must be earthed after proven de-energised – Consider taking this out considering the installation being worked on wasn’t high voltage and is a secondary control after isolation
Securing the isolation: lock the isolating switch(es) or remove and tie back relevant conductors to protect the people carrying out the electrical work
Tagging: tag the isolation points where possible to provide general information to people at the workplace
Testing: test to confirm the relevant circuits have been de-energised along with any other relevant conductors in the work area, and re-test as necessary.
The safe work principle TEST FOR ‘DEAD’ BEFORE YOU TOUCH must be applied at all times.
Important information for meter installers
Installing or replacing an electricity meter requires the proper isolation of the electrical supply at the Service Protection Device (SPD) before proceeding. If the SPD is missing or inoperable, workers must stop work. An isolation on the distribution network must be arranged before proceeding with the meter installation.
Managing Electrical Risks in the Workplace – Approved Code of Practice