Transformer fault current

[peterpylon]

General system fault level is specified at 35kA

Part of installation involves small isolation 50kVA Tx's before dist boards for lighting & small power etc. (415/433V)

What is best way to calculate expected max fault level to be expected at secondary terminals? Z = 6%

I am looking to rate the DB's at around 16kA

Any help would be appreciated.

Thanks in advance
Peter

 

[davidbeach]

50kVA 3[Ø] transformers, 415V secondary voltage, 6% impedance, connected to an infinite bus on the primary will have 1159A of fault current on the secondary.

50/(0.415*sqrt(3)*0.06)=1159A.

I wouldn't worry about complicating the calculation by trying to include a less than infinite source on the primary.

 

[wareagle]

David
I used a single phase transformer.
50kva/0.415 = 120 amps/0/06 = 2000 amps phase to phase and
about 3000 amps phase to neutral.

 

[peterpylon]

Thanks Guys

Very helpfull

Regards
PeterP