Available current and transformer inrush
Available current and transformer inrush
(OP)
I'm working on a 12470V distribution system with a max available fault current ~5000A. For math simplicity, let's say the system feeds ten 2,000kva transformers. When determining xfmr inrush, 10 times fla @ 100ms is a number commonly used as a estimate. Fla @ 12470 is 92A per xfmr. Estimated inrush per xfmr of 920A.
So when the system is initially energized, the calculated estimate for inrush of all 10 xfmrs is 9200A. The available current of the system is only 5000A. What's the explanation for what is happening here? Are the transformers just taking longer to energize since the available current is less?
I am trying to set the instantaneous for the phase overcurrent protection, was going to set it just above 9200A to avoid problems with inrush, then realized this would be the same as disabling it since max available is 5,000.
Any help on this issue is appreciated.
Thanks.
So when the system is initially energized, the calculated estimate for inrush of all 10 xfmrs is 9200A. The available current of the system is only 5000A. What's the explanation for what is happening here? Are the transformers just taking longer to energize since the available current is less?
I am trying to set the instantaneous for the phase overcurrent protection, was going to set it just above 9200A to avoid problems with inrush, then realized this would be the same as disabling it since max available is 5,000.
Any help on this issue is appreciated.
Thanks.






RE: Available current and transformer inrush
S&C had a paper on this on their website in the past, but I don't know if it is still accessible or not.
RE: Available current and transformer inrush