Transformer Cable Temperature Rating Question

[tumbleweed1]

I have a 1.5MVA transformer with a 600V secondary. The transformer is a 220 class transformer so 40degC Ambient + 150degC Winding Rise + 30degC Hot Spot = 220degC.

My question is: What temperature ratings do the cables have to be?

If you were to analogously compare a transformer insulation to motor insulation, CECode says Class F/H insulation requires 110degC rated cables.

Does the same apply to transformers? I mean, do the connection points on a transformer rise to 150degC and do I need to be concerned that a 90degC lug or Teck90 cable is inadequate??

Brings me to another point, even if I use 110degC rated cables, I dont know of any compression lugs rated past 90degC.

This temperature rating is always something that I am unsure about.

 

[prc]

Even if thermal class is 220 C ,normally actual winding temperature will be much less than that. Better to contact manufacturer for actual bushing terminal pad temperature. If it is anything near 100C should give a silver plated pad to reduce oxidation.

 

[7anoter4]

NEC Art.110.14 (1) Equipment Provisions.
If the transformer manufacturer states the terminal maximum temperature then
the ampacity of the connected cable may be close to it if the maximum permissible temperature of the cable it is not less.
For instance ABB recommends 105oC maximum bushing [GOH] temperature.
If we don’t know the terminal maximum allowable temperature then:
(a) Termination provisions of equipment for circuits rated 100 amperes or less:
(1) Conductors rated 60°C (140°F)
2) Conductors with higher temperature ratings provided the ampacity of such conductors is determined based on the 60°C (140°F) ampacity of the conductor size.
(b) Termination provisions of equipment for circuits rated over 100 amperes:
As for above a) except temperature of 75oC instead of 60.