Is this a legal connection? Does it violate any code rules?

[mbk2k3]

I'm attaching a sketch to make it 100% clear what I am trying to do. See attached JPG.

https://imgur.com/a/1kLdd2p

This is for an 8 month rental project where they are renting generators and are looking to parallel the 3. There is no space for a new switchgear / 'splitter' to tie the 4.16kV connections together.
Someone brought up the idea of adding a jumper cable between the two transformer HV cabinets, to tie the 4.16kV sides together.

I've never seen an arrangement like this, but I can't find any rules/code violations either. This is located in Canada, but I'm open to NEC applications and code rules if there are any.

I've verified that the transformer and transformer bushings can withstand the short circuit contribution from the 3 generators.
I've verified that the 4 hole nema pad on the HV bushings are good for the FLA of 2x generators (most that any bushing will see).
I've verified that the 250MCM cables are all adequate in terms of carrying the expected load currents and can withstand the short-circuit currents as well (generator protections trip quite early).

But I just can't wrap my mind around the fact that this is an unorthodox arrangement, and I'm looking for code rules that discuss:
- tap conductors
- using the HV cabinet as a JB/raceway even though the 4.16kV cables are all terminated within
- any other rules?

Would like to beef up my argument for this arrangement if I do go ahead and submit it to the local inspection authority for approval.

 

[waross]

Isolation?
Overload and over-current protection?
Synchronizing gear?
I once saw an installation where a structural member reduced the clearance in front of a panel to less than the code minimum because there was "No space".
After major structural modifications there was enough space and the installation was passed by the AHJ.
That was in Canada by the way.
The generator rental people may be able to supply the required switchgear and synchronizing equipment.
Do you have room to go up?
Mount the switchgear in sea-can and put one of the generators on top of the sea-can?
I have seen the creative use of stacked sea-cans when space was limited.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[mbk2k3]

i didn't show circuitbreakers for simplicity sake.

each generator has its own CB with protection relays and PTs for synchronizing. these breakers also protect the 4.16kV cables and transformers.
each generator has a controller that can be used for load sharing/dead bus closure/etc.

transformers have a breaker on secondary side as well.

the gensets are containerized (by VENDOR A) and already set in place, as well as the transformers (from VENDOR B). moving things around will cost big bucks in rental equipment, and also there isn't much space to put in place a 5 cell switchgear lineup. plus not sure if rental vendors will allow such modifications.

this is also in canada btw.

everyone i speak to suggests putting a switchgear in between, but no one has told me if the proposed sketch is violating any NEC / CEC rules.

 

[bacon4life]

The image without the clicking:

 

[mbk2k3]

thanks, didn't think of embedding the image in the post. appreciate it.

 

[waross]

The person to ask is the AHJ.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[BrianPetersen]

In Ontario, this would be a question for the local Electrical Safety Authority inspector.

 

[LionelHutz]

I don't see why not as long as the cables are all properly sized. The jumper could see current from 2 gensets and the TX pads could see current from all 3 gensets.

If you want to make it look more "orthodox" then use a jumper box to connect everything. Cables from all 3 gensets to this box and then 2 cables from the box to the transformers.