De-energise equipment before starting any electrical work to prevent burns, injury and death caused by an electrical arc flash. If the job requires you to work live, control the risks and follow safe work procedures.
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When you woke up this morning you thought this would be a day like any other.
You've been called in to do a quick job, change a circuit breaker. No big deal. You've done it a million times before. You aren't going to rock the boat by asking for the power to be shut down. You'll just do it live. It'll only take a second.
What you don't know is in the six months since this panel was last opened, dust has built up between live parts. There's a loose screw waiting to drop at any minute, and the insulation on the bus bar is old, worn and about to crack.
But that doesn't matter. Whatever the reason, you're working on live, energised equipment and this is about to happen.
[High pitched tone]
So what just happened, you just experienced an arc flash. An unexpected, violent electrical short circuit where current flowed between the phase conductors, neutral and Earth. When that electrical arc fault occurred, the following things happened.
The arc caused a superheated ball of flame to erupt around you. A fireball that reached 20,000 degrees Celsius in a fraction of a second. That's four times hotter than the surface of the Sun. And it happened 30 centimetres from your face.
The copper conductors vaporised and expanded up to 67,000 times their original volume, culminating in a shower of molten metal flying directly at you.
The vaporised metals, smoke and burnt components formed a boiling, poisonous gas that engulfed you and went into your airways.
The pressure wave knocked you off your feet and into the wall behind you. Collapsing your left lung.
Thankfully, you survived.
Your hands took the bulk of the heat blast, causing third degree burns. You'll need skin grafts and months of rehabilitation. If you had worn the correct protective gloves, you could have reduced the risks and avoided serious burns.
Your front and back were badly burnt, with second degree burns across your chest from the initial blast, as well as a patchwork of first and second degree burns where your shirt caught fire. If you had been wearing the correct arc-rated protective clothing, it could have prevented the arc flash from setting your clothes on fire.
None of this would have happened if you had assessed the risks and deenergised the switchboard before you started work.
But it's too late now.
You will never regain the full use of your hands, so you may not be able to work as an electrician again. You'll be off work of any sort for months. On top of the injuries and lost wages, you'll also have fines to pay.
If there are energised parts; expect the unexpected and protect yourself against arc flash.
Always follow safe work procedures and wear appropriate PPE to reduce the risks of serious burns, injury or death.
Remember, the only way to eliminate the risk of arc flash is to choose not to work live.