What Is An Arc Flash?

What Is An Arc Flash?

Now that we have a good idea about electricity and shock, we can finally get into what an arc

flash is and just how dangerous it can be.

An arc flash is a short circuit through the air in an electrical panel box or any other piece of

energized electrical equipment. Air, as you have already learned, is normally an insulator, but

with a high enough voltage, a slipped tool, or a panel box that is dirty, the circuit can be

completed, causing a short.

When the short happens and the circuit is completed through the air, the air breaks down to

where it offers little‐to‐no resistance to the flow of electricity.

Remember, this is what a short circuit is. A short circuit will have almost zero resistance and will

have very high levels of current. The high current is what is responsible for the arc flash.

The tremendous amounts of energy released in an arc flash make for a very bright, very hot, and

very loud explosion.

Arc Flash vs. Safely Completed Circuits

Higher than normal currents

Now in a safely completed circuit, such as when a motor turns on a manufacturing line, the

circuit is complete, just like in an arc flash, but a safely completed circuit has a load on the

circuit offering resistance.

So in a safely completed circuit, the resistance affects the current in the circuit, keeping the

current under dangerously high levels.

Think of a lamp plugged into the outlet of your house. When you turn it on, the circuit is

completed, but the light bulb has resistance, so the current stays within safe limits.

If you were to stick a paper clip in an outlet, the circuit will also be completed, but this time it

will be a short circuit because the metal paper clip offers very little resistance to the flow of

electricity.

By the way, NEVER stick a paper clip into an electrical outlet. It is dangerous, and if you do it you

will receive an electric shock or worse