Ok Mr. MBooke,
I understand short circuit as existing between phases, and a ground fault to go to earth.
Almost, they go back to the source. That would be the utility transformer via the incoming service neutral.
Semantics yes, but if we are to describe 'arc' as a different electrical phenomenon, we need to clear this up first.
I think so.
Let's focus on Ground faults , as it seems the repackaged residential terror , at least to the electrical marketing world....
That it is unfortunately.
What is a Gfault? , How does it occur, how is duration vs. impedance a factor?
~RJ~
For the sake of this conversation a ground fault is a short circuit between the line (phase) to the equipment grounding conductor or any piece of metal bonded to the equipment grounding conductor.
It works like this. When a short circuit occurs whether a breaker trips thermally or magnetically determines the duration of said fault. When a short circuit magnetically trips its breaker the fault rarely lasts longer then 3 cycles. Magnetic trip has no delay. Now, when a short circuit current is below a breaker's magnetic trip the time it takes to clear a short circuit is a bit longer. It will take over 3 cycles because the bi-metal must heat up first before any action takes place. If the arc sputters this also increases the time a bit. The reason being that when a short circuit sputters the fault current is not fully sinusoidal, it varies in the sine wave. Thus the sputtering fault adds more time to the bi-metals unlatching time.
What determines if a short circuit trips a breaker magnetically or not are two things:
1. The impedance of the circuit. This is further broken in two parts:
a. the impedance of the wire from the panel to the fault. (length and gauge determine this impedance).
b. Fault current from the utility, which basically boils down to the transformer's impedance and that of the service conductors.
2. The magnetic trip threshold of the breaker itself.