I am designing electrical system for a power plant. I need to know the BIL of 5 MVA, 13.8 KV synchronous generators for the insulation level coordination studies. But the generators do not have BIL ratings, to do the calculation I am making following assumption.
Synchronous Generator Insulation level
I know the rotating machine winding can withstand a voltage wave with the crest value of 1.25 times the hi-pot test voltage in 10 microseconds. There is a formula in IEEE for the value hi-pot test voltage for stator coils during manufacture, which is test voltage = 2*(2U+1).
Using this criteria the value of crest of voltage wave would become 2*(2*13.8+1) *1.41*1.25=100.815 KV
Can I consider 100 KV as a BIL of this these generators in my insulation level coordination studies?
What is your experience on this? How do you deal with synchronous generators BIL?
I need your expert judgment on this, together with reference to relevant standards