High voltage conduit bend radius

[dema]

I have to run a conduit for a utility 13.8KV primary feed through a tunnel. I can't do that within a building, so I am having to encase it in concrete. This concrete curb has to run up a 55" ledge. The turn radius for a 4" conduit is absolutely essential as you can imagine.

The NEC tables state 24". However, I looked something up previously and got 42". I don't know if I just got literature on a wide sweep tool or what, but I am concerned that there may be different rules for over 600V than for under 600V.

Do you know of any rule increasing the 24" turn radius?

 

[Smart $]

Depends on the conductor...

300.34 Conductor Bending Radius. The conductor shall
not be bent to a radius less than 8 times the overall diameter
for nonshielded conductors or 12 times the overall diameter
for shielded or lead-covered conductors during or after installation.
For multiconductor or multiplexed single-conductor
cables having individually shielded conductors, the minimum
bending radius is 12 times the diameter of the individually
shielded conductors or 7 times the overall diameter, whichever
is greater.

Keep in mind the above section is from Part II ...over 1000 Volts, Nominal.

And you may want to verify the above with the cable manufacturer.

The next thing to consider is pulling tension....