Portable power cable, generator breaker

[Dsg319]

Have a big gen set with a 2500amp main that is feeding 3 VFD’s.

I’m not responsible for load side of vfd to the pump but only supplying power with portable power cable that has already been supplied from the general contractor and rental company. Type W, TF CABLE. Size 4/0 with ampacity of 405amperes.

Running parallels 2 conductors per phase will terminate in a 800amp breaker in the vfd.

I know I have to size my EGC from the source breaker feeding (2500amp) which would be a 350mcm.

My only question is since this type of cable has a higher ampacity than typical do I still size per 250.122?

I know grounding conductors need not be larger than phase conductors so I was just going to install two 4/0 for my EGC as well.

I am just wondering if it was still sized per 250.122 which I believe it should be.

 

[don_resqcapt19]

It does not have a higher ampacity when used in an NEC application. That ampacity is for free conductors in open air at 90°C and cannot be used
As far as the equipment grounding conductor for a parallel installation, the sum of the areas of the conductors connected in parallel for a single phase is the size of the conductor for the application of "The equipment grounding conductor shall not be required to be larger than the circuit conductors supplying the equipment."

 

[Dsg319]

It does not have a higher ampacity when used in an NEC application. That ampacity is for free conductors in open air at 90°C and cannot be used
As far as the equipment grounding conductor for a parallel installation, the sum of the areas of the conductors connected in parallel for a single phase is the size of the conductor for the application of "The equipment grounding conductor shall not be required to be larger than the circuit conductors supplying the equipment."

Thanks Don.

 

[zbang]

Table 400.5(A)(2) gives 405 amps for 90C but not in raceways and not bundled (footnote 1), you're probably looking more towards the 75C column "E" for 317 amps. But.... you can run & rate the cable at 90C and 405 amps but have to use 250kc else to get to 75C for terminals.

FWIW, last I checked E1016 Camloks (the usual size) are rated for 105C.