about distribution system

[teptep]

Please help. Here's the question...
For a building having transformer of 2,000 kVA, 34.5kV-460V, what is the short circuit interrupting capacity (in kAIC) of main circuit breaker on the low voltage side of transformer?

 

[tkb]

Not enough information.

Need the impedence of the transformer, secondary conductor size, conduit type, wire length, and wire type CU or AL.

 

[teptep]

can you give an assumption?

 

[tkb]

Never Ass-U-Me

 

[bradleyelectric]

can you give an assumption?

can't do the math without the numbers.

 

[Pierre C Belarge]

can you give an assumption?

Very low to very high....assumptions in the electrical industry can only lead to trouble.

 

[jim dungar]

Please help. Here's the question...
For a building having transformer of 2,000 kVA, 34.5kV-460V, what is the short circuit interrupting capacity (in kAIC) of main circuit breaker on the low voltage side of transformer?

Are your questions out of a text book? I believe it should be asking for the required minimum kAIC and the secondary voltage should be 480V.

If you want a precise answer than you need more information.
If you want an approximate answer for the available fault current, the industry standard (but not guaranteed) minimum is %Z=5.0 for this size transformer. Of course you should also make assumptions about the transformer X/R ratio and impedance tolerances.

 

[teptep]

ok thanks for the info.

 

[weressl]

Please help. Here's the question...
For a building having transformer of 2,000 kVA, 34.5kV-460V, what is the short circuit interrupting capacity (in kAIC) of main circuit breaker on the low voltage side of transformer?

The information you supplied is not sufficient for an accurate answer, but as a rule of tumb the worst case for a typical 5.5% impedance transformer at infinite utility SC on the primary you would be looking at about 55kA symetrical SC duty.