Routing of 34.5 kV into building

[EEJaime]

Gentlemen,

I am designing a building wherein the service is delivered at 34.5kV metered at the utility company yard on-site. I am routing this on-site through a series of Manholes to a point adjacent the building. I am bringing in two, 3 phase circuits to feed through a primary feed selector transfer switchgear lineup. This will subsequently feed through SF6 filled sectionalizing switches to subfeed the series of substations I need to transform to my utilization Voltage of 480Y/277V,3ph,4w.

This is my question:
The Apron level finished surface elevation exterior to the building is at +26.5'. My finished floor elevation where the switchgear will be located is at +4.5'. The switchgear is 22 feet, (about 7 meters), below the top of the manhole. Even if I use a fairly deep manhole of say 8 to 10 feet and have the conduit exit some distance above the manhole bottom, I am still concerned about water entering the conduit and syphoning down to the lower level. What is the best conduit/cable sealing system that you have experience with?

There are numerous foam sealants that are used to fill such openings, however..., and this is the kicker. These manholes are located at an airport gate apron. they are within the fueling port distance requirement that makes any area below grade, a Class 1, Division 1 atmosphere. Do any of you gents have any experience with a device or assembly that will seal a conduit and cable entry from a manhole? I've Googled till I'm light headed, and the manufacturers I am familiar with, Appleton, O-Z Gedney, don't have this configuration or size.

The cable will be 35kV MV-90, 133%,XLP with PVC jacket, #4/0 AWG max. (3)-1/c cables in a 4" PVC schedule 40 conduit with the conduit banks concrete encased.

Any guidance is appreciated,
EEJaime

 

[davidbeach]

Bring the cables into a pit below the switchgear rather than in above. provide drains, and sump pumps if necessary, for the pit that can drain water out faster than it can enter from the manhole. Assume that all seals fail.

 

[davidbeach]

Missed the airport apron area on first read through, best to find a different location for your manholes.

 

[EEJaime]

Well that is a conservative approach that I had not considered. And if I assume that the pump will fail, I'll specify a duplex standby pump. Any ideas about keeping out Jet fuel fumes?

 

[EEJaime]

Ii wish that I could relocate the manholes. The concourses are double loaded with the tug ramps and Passenger boarding bridge piers severely limiting the available areas. We are also contractually limited as to the areas and distance from the building that we are allowed to use.

Hell, I had to squeeze my generators between two 3-level building wings that will require the DaVinci of crane operators to drop in without bouncing them off the glass buildings.

You have got to love them Architects!

 

[jghrist]

Can you enter the building at a higher level and use cable tray to go to the lower level indoors?

 

[EEJaime]

jghrist,
That is a very good idea. I need to do a little code research on the implications of routing 34.5kV cable through interior spaces, but if I can limit it to the electrical room spaces accessible only to qualified personnel it might just work.
Thank you,
EEJaime

 

[lansford]

You may give some thought to a CLX/TECH cable. With the correct end sealing fittings, I think they are good for classified locations. They are used a lot in refinery and petrochemical.
JIM

 

[Marmite]

I can recommend this sealing system if you are forced down that route.

http://www.csdsealingsystems.co.uk/products/rise.html

Regards
Marmite

 

[EEJaime]

Marmite,
Excellent products. I tried to contact them to ask if they supplied their product to the US, but the website sucurity would not accept our telephone number which it did not recognize as a valid number. I tried inputting a dummy number in the correct format, but did not succeed. I get the feeling that perhaps they do not regularly do business in US as the system would not take the number even with the requisite international code.
Thank you for the link, it is just the thing I am looking for, now I just need to find it or something like it in my corner of the world.
Regards,
EEJaime

 

[BJC]

Google up "Jack Moon" Very good seals that will hold back water. I thin they are part of Tyco.
I have had to put outside disconnects in such installation. I am not sure it was code, FAA or just an inspector. I used a remote shut off control switch. The rational was what do the firemen do when they get to the fire? Not many want to run in with hose when there is 12Kv about, not crazy about 34.kv either.
The inspector who made me do it was an experienced air port firefighter. It seemd like a good ideal, I would still do it.

 

[ScottyUK]

Jaime,

Try using a number like 01642 442140, no codes or anything. That's my old desk number with a former employer and as far as I know it's not been re-assigned yet. Maybe include a note in the comments that it's a dummy number to allow registration.


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If we learn from our mistakes I'm getting a great education!

 

[EEJaime]

Thank you Scotty!

It finally took my query. It rejected it initially as I entered a dash (-), between the two series of numbers you provided. I explained that the number was not valid, and provided our correct number so your employer will hopefully not recieve calls from a "sales engineer" looking for someone not there.

I found some information when I googled them with a 'US' tag, but it was for an industrial sales office on our east coast and does not look promising.

I appreciate your assistance,

EEJaime

 

[ScottyUK]

No problem at all.


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If we learn from our mistakes I'm getting a great education!