davidbeach, sorry my wording above, i meant fault through transformer gets reduced by grid impedance plus self impedance. 3120/(0.061+(480/56398))= 44892 which is less than transformer through fault capacity.
So why to match with utility SC value?
Thank you waross & bacon4life for your input.
Waross, Since it is "SC" rating that has been rated for 3s for mv switchgear, i believe transients are not much of a concern here. So far i have seen for any sc(phase/earth) which is quite a high value 50P is set to trip instantaneously, in some...
Why do MV Switchgear are rated for short circuit rating 3s?
I have seen (limited to my experience) tripping time in relays is within 1S for faults. Overcurrent it may be more based on current value, but that doesn't a concern to SC rating.
Even if I consider NGR current limiting to much lower...
