High Voltage Transformer Termination

[augie47]

I seldom inspect > 600v. I have a job with a 12kv & 4160 circuits.
The design calls for a 4160 circuit from a 2500 kva pad to 4160 gear with (3) 350 kcmil 5kv cables supplying 400 amp fuses in the gear.
The engineer is referencing 310.77 showing 415 amp at 105?C.
Is it common for transformers and 4160 gear to permit 105? terminations ??

 

[bwolf]

I believe you use the 90? column unless the terminations are otherwise identified. See 110.40.

 

[augie47]

Great reference.. one would think an inspector would know that one Thanks.

 

[ron]

Agree with bwolf.

 

[mivey]

We stop at 90 deg. This is from the historical 90 deg continuous, 130 deg emergency rating (emergency rating not recognized in the NEC but are by utility standards). Now they have a 105 continuous and 140 emergency ratings. The problem might be finding PVC rated for 105 if using NMC. There are conductors and terminals rated for higher than that also.