Basic Electrical Safety

Fire Due to Short Circuits

A short circuit most commonly occurs when a line to ground fault takes place in a system, although a line to line fault is also another form of a short circuit. Under either of these conditions, resistance will in effect go to 0 and as a result, current will attempt to spike towards infinity.  When current increases in such a drastic manner even protective circuit breakers with grossly oversized trip values will open up and cut off the current source. Design features that protect against short circuit conditions are relatively easy to protect against.  A short circuit will most commonly result in a fire when a ready source of fuel is present, such as a flammable atmosphere or combustible plastics. In these cases even a fault concern that is quickly cut off by a circuit breaker can result in a fire.  The solution to this problem is to eliminate the source of fuel.  When dealing with a flammable atmosphere the previously discussed 240VA limit does not apply.  The reason for this is that even a very small spark can ignite a flammable atmosphere.  In these case the common solution is to ensure that electrical energy and flammable atmospheres can never come together even under fault conditions.