The standard for industrial power breakers with several hundred amperes is, that they hve to be able to safely shut off even in case of a total short circuit. So exactly what you mentioned, at the given voltage the breaker will not meltdown. to kill the arc, these breakers (also the samll household ones) have "loeschkammern" (i dont know the word), small metal plates in a row to weaken the arcs power and finally extinguish it.

If the poco's transformer short circuit power is bigger that the short switching capacity of your breaker, you have to install another breaker or (mostly here) big melting fuses with enough switchoff capacity.

with these precautions, and assuming the power transformer works correctly, you wont run into a meltdown nowhere.

just different if you've got an overvoltage on the line due to a transformer coil failure ect.
thats why most (all?) high amperage panels are equipped with surge detectors, also capable of at least the switchoff capacity
of the fuse they are connected to.
they short the line out in case of overvoltage, causing the fuse to blow. These are one-time surpressors, after one strike they're dead.

i've seen boxes for them with a clear front that spring mounted. The tripping detectors would break the cover if it wouldnt lift up [Linked Image]


to come back to the breaker at home: i've never heard f dangers in resetting a shorted breaker. never heard of anyone that heard of anyone who dreamed of someone that heard of this.
the standard after a breaker tripped here is to assure no one is in danger and switch it back on. if it bangs and the breaker tripped again, go for a search.

[This message has been edited by :andy: (edited 02-28-2004).]