Step Up Transformer

[mustang17]

Project for a small local utility service entrance at a Water Treatment Plant. Using a 250KW, 480 generator to step up to 12470 Y. Generator sizing and recorder data indicate these are very comfortable numbers. Using automatic transfer switch to select between utility power or generator power. 12470 Y is then distributed throughout the water plant.

Question is the plant has 6 services. Combined they have about 1000KVA of transformers. Peak loading over two years never exceed 140 KVA combined. We are stepping up the individual loads on the services but I wanted to account for the transformer inrush currents. I know the KVA of each service and the impeadence. Do you know the formula or how I should go about accounting for this unloaded transformer inrush. At these levels is this even a concern?

 

[jghrist]

See Overcurrent Protection of Transformers — Traditional and New Fusing Philosophies for Small and Large Transformers

http://www.sandc.com/webzine/012003_1.asp

for a discussion of transformer inrush.