Arc flash incidents reported
Workplace Health and Safety Queensland has advised that two electrical workers suffered burns following an arc flash incident in January this year. They were working in a switch room with an LV main switchboard. Initial inquiries indicate electrical work was being done on the switchboard metering when the incident occurred.
The following month, an electrical worker was injured working near energised electrical parts in a switchboard. Early investigations indicate he may have been trying to move cables in the switchboard that stopped the escutcheon panel closing. The tool being used by the worker to move the cables appears to have contacted energised parts, causing a short circuit and arc flash.
Workplace Health and Safety Queensland says that the findings are not yet confirmed and investigations into both incidents are continuing to determine the exact cause, but the department does offer the following safety issue information as a reminder for electrical workers.
Working in switchboards carries a greater risk of injury because of high fault currents and often the work is done in confined areas.
If you have to work live — for example, when testing or fault finding — you must conduct a risk assessment. The risks associated with performing work near exposed live parts can be equivalent to those associated with live work. Typical risks include:
- electric shock if exposed energised parts are touched;
- explosion — for example, if a metal tool is dropped onto bus bars causing a short circuit;
- exposure to high-temperature parts, causing burns to bare skin;
- electrical fires induced by allowing moisture or dust to enter electrical equipment.
Ways to manage health and safety
Taking steps to manage risks is a condition of doing business. Effective risk management starts with a commitment to health and safety from those who manage the business. If an incident occurs, you’ll need to show the regulator you’ve used an effective risk management process. In Queensland, this responsibility is covered by your primary duty of care in the Electrical Safety Act 2002.
If there is a safety risk associated with working near energised electrical parts, a written risk assessment should be conducted to determine the risk level and appropriate control measures. For the risk of arc flash, the risk assessment must consider the level of possible fault current present at the board considering:
- the physical size of the switchboard;
- the size of the incoming consumer mains;
- high fault current ratings of circuit protection devices;
- the presence of fault current limiters on the switchboard;
- transformers located near the switchboard.
Use the hierarchy of control to decide how to eliminate and reduce risks in your place of work. The hierarchy of controls ranks types of control methods from the highest level of protection and reliability to the lowest. It’s a step-by-step approach to eliminating or reducing risks. You must work through the hierarchy of controls when managing risks, with the aim of eliminating the hazard, which is the most effective control.
Possible control measures to prevent similar incidents
Effective control measures for arc flash related incidents are often made up of a combination of controls. Always test before you touch and never assume parts of electrical equipment are de-energised. Turn off the power to the entire switchboard, even if this means rescheduling the work to another time.
A safe system of work or safe work method statement for managing the risk of arc flash should include:
- electrically isolating nearby electrical equipment or installation before starting work, and ensuring it can't be reconnected while the work is being carried out;
- using insulated or non-conductive physical barriers to prevent inadvertent contact with energised parts;
- ensuring people not required for the work are excluded from the area (using screens, barriers and signage).
Risks can be further minimised by implementing administrative and personal protective equipment (PPE) controls. Examples include:
- ensuring workers have appropriate knowledge and skills to perform the work safely;
- provision of suitable and adequate training, establishing exclusion zones, and use of permits and warning signs;
- ensuring testing procedures are in place to prove parts are de-energised before work commences;
- ensuring workers have tools, test equipment and PPE suitable for the rated level of fault current;
- consider the use of a safety observer.
Adopting and implementing higher order controls before considering administrative or PPE controls will significantly reduce the likelihood of a similar incident occurring. The control measures you put in place should be reviewed regularly to make sure they work as planned.
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