Please Explain: Symmetrical fault current

[daveede]

That might be it

How does it effect all 3 phases if you consider only 2?
and why is it then considered different to the normal 2 phase pscc?

Thanks for helping me

 

[topquark]

Remember it's prospective (IE what could the maximum be). The minimum will be 0 (or as close to it as the real system would allow for). Remember we're considering a mathematically perfect system here (always will be some "real world" error, maybe one of the phases is slightly out etc).

So your fault could be a short between all 3 phases, so far so good. If you (during investigation, ignoring ESC) were to grab two of those phases thats what would flow.

 

[topquark]

How about this as a (maybe better) scenario. You have a fault involving all 3 phases (a short between all 3 phases/cables). The supply then drops a phase whilst that fault exists. That will then give you your maximum current of square root of 3 X (assuming minimal resistance for the short etc).