3/8" EHS steel class A coating, fault withstand rating?

[NAZ55]

Does anyone here know the fault withstand rating of EHS steel conductors?

Even if you can provide me with Kf and Fusing Temperature values to use from IEEE 80 - Table 2 it would be a tremendous help.

Thanks

 

[jghrist]

Why not use the values for Zinc-coated steel rod in IEEE Std 80 Table 2?

 

[NAZ55]

Because I don't really know the effects of having multiple zinc-coated strands vs solid steel rod (skin effects etc). IEEE-80 also doesn't specify what type of steel was used in the rod and how thick the zinc coating. So lots of unknown there. I figured someone may have already obtained that information from a wire manufacturer.

 

[jghrist]

See "Rating of Conductors For Short Duration Currents", V.T. Morgan, Proc. IEE, Vol. 118, No. 314, March/April 1971.

This has a much more complex treatment of short circuit rating than the simple adiabatic equation in IEEE Std 80. Morgan also lists properties for several conductor materials, but only for steel, not specifically EHS galvanized.

I compared Morgan's method with IEEE Std 80 for #1/0 Cu for 1/2 cycle and got 35,148A vs 31,724A. Not much difference. I question the need to get too precise when the assumptions of no heat loss and ambient temperature estimates are considered.