15 kv ampacity

[augie47]

I don't deal with over 600v often enough to be half knowledgeable so I could use some verification here.
In have a customer owned arrangement with a 4350 KVA 12.4KV/575V 3 phase transformer.
Primary protection is 300 amp fusing. Primary wiring is muticonductor cable mv105 in cable tray transitioning to conduit. Termination ratings are unknown, possibly 90?.
E/C has elected to use 4/0 Cu cable. Based on 310.60(C)(73) {'11 Code}, I see no problem.
Am I overlooking something ?

 

[Ragin Cajun]

4/0 is good for 295A @ 90degC. Table 310.73 since the cable is in conduit part of the length. Cable looks OK, assuming the ambient is less than 40degC.

Per Table 450.3(A) the fuse looks a bit on the low side. Perhaps they are using only a 300A fused switch?

4250KVA is ~200A @ 12.47KV, thus the 300A fuse is 150%. Is this an OA transformer or are there FA, FOA, 65degC, etc. ratings?

Is there secondary protection? Is it a "supervised location"?


RC