Anyone tell me what are typical maximum inrush values one can expect on large autotransformers (>200MVA, >=220kV)? I need to set the diff hi-set element on a 375MVA, 275kV unit.
This seems to be the general rule of thumb for trfr inrush. But I have also seen that for small units (< 5MVA ) it can be up to 10p.u. and someone said for large autos you can look at 2.5p.u..
Are there perhas more specific rule of thumbs depending on trfr size?
No thumb rules.Inrush varies due to various factors.Transformer size is a parameter. In a voltage transformer it can be 25 times rated current. In a distribution transformer 10-15 times FLC.Power Transformers 8-12 times and very large units 3-5 times.For the size mentioned by you and for auto transformers the range mentioned by me is normal.