Hello, can someone explain in layman's terms how arc flash happens and what arc flash is. I have browsed wiki and google but I think I'm still missing it...

Arc Flash is the sudden release of high pressure, high temperature gas and debris caused as a result of electrically conductive metals being tranformed from solid to gas state during rapid melting. In example form, you are working in a electric panel, and your screwdriver bridges across two phase conductors. V=IR, so if V is constant, and R goes to near zero, the I goes to near infinity. So much current through such small bus bars causes them to melt almost instaneously, and convert from solid to gas state. The gas is expanding in all directions, including toward the worker. The gas is super hot so it would severely burn the worker if he wasn't protected. The visual effects is one of an 'explosion'.

There is more to it, but thats the layman's version.
Check out youtube and search for arcflash and watch some of the videos.

Are you not explaining more of an Arc Blast rather then Arc Flash. My understanding is that an Arc Flash is the result of an arc being created by an electrical source that has both high enough voltage as well as sufficient current capability that it will ionize the air around the arc, causing a ball of superheated gas that will cause burning. If either sufficient voltage or sufficient current are not available, an Arc Flash will not happen.

It was also my understanding that if there was metal involved where you were converting the solid metal into a gas, that the resulting expansion in the relm of tens of thousands of times of the metal will create an explosion called an Arc Blast.

Maybe I missed something in the definition?

Arc Flash definition

I am also a bit confused about what happens with the electricity in an arc flash. I understand the basics, but what i'm now wondering is:

a) Does an arc flash require the electricity to travel in a completed circuit? Or does it involve the electricity being dispersed into the air? I'm trying to understand how the electricity can be released into the air because I always thought it would try to find its way to "ground".

b) Will an arc flash always require crossing through the air? In other words, if an electric current went straight from an electrical bus through a person to ground, would it always product an arc flash? Would a high-voltage electrocution always produce an arc flash?

a Yes a complete circuit. No it doesn't disperse into air, it travels through ionized air. No it does not necessarily seek ground; ground must be part of the circuit.

b Arcs can occur in other mediums, but the air shared with people is where injuries occur. Direct contact can cause arcs as electricity flashes over the skin and when a person moves to break the circuit. Not really considered an arc flash incident though.