If you had a choice,,,,,,,,,,

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dicklaxt

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Here's the scenario.

Powerhouse, housing 13.8 Switchgear, elevated 6' above finished grade.
Okay so how do you want to run the feeder cables from the Switchgear to transformer HV chambers. This will be 3 phase 13.8KV shielded cable,the 6 transformers are 13.8-4.16 KV @ 20MVA each with a full height chamber from grade to above HV Bushings,removable door/cover.

Max feeder length to transformer #6 is 150' with 2 vertical 90's and 1 horizontal 90 when going UG,AG conduit run would probably have 2 additional 90's.Quick calcs on load at 125% is 1050 amps

Your options are :

1.Overhead in cable tray triplexed or multiconductor.

2.Rigid UG conduit with singles or multicondutor out the bottom of gear,UG encased in concrete and stubbing up into the HV chamber.

3.Direct buried cable either triplexed or multi conductors stubbing up into HV chamber using rigid conduit sleevs at both ends.

4.Overhead in rigid conduit out the bottom of bldg or thru wall,dropping down into the HV chamber.

I don't usually have these type options available as the plant specs always direct the design to be to their standards. This contract is very cost conscious and after safety and code requirements are met its potluck ,get it done, quick and cheap.The client has not specified a preference.

You as the field guy probably don't usually have this latitude either so lets make it easy on you too.

dick
 
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dicklaxt

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On a knoll behind a 27' high tidal surge wall but soil conditions are still sandy and with a shallow water table.

dick
 
kingpb

kingpb

Senior Member
Location
SE USA as far as you can go
Occupation
Engineer, Registered
Go out the bottom of the switchgear and transition into PVC conduit. If the conduits are not directly under the desired cubicle, mount some cable tray to the underside of the elevated building to get you routed to where you need to be. This is the traditional and universally accepted approach. Use cable glands on tray rated MV cable to attach to the removable (drill-able) plate going into bottom of switchgear.
 
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dicklaxt

Guest
I guess the question was not clear,I'm not looking for the way to do it but the easiest way and/or preference of the man in the field(electrician doing the work-"YOU")

What would be your preference of the 4 options above?I guess you must consider the labor costs to you,the difficulty of each option reflected in the time frame one versus the other,etc.

I will put this on paper,I'm trying to make it easy and to "YOUR" liking,so name your poison,the drinks are on me.
(1st round only,LOL)

dick
 
weressl

weressl

Esteemed Member
Location
Texas by the Gulf, geat crab, great shrimp
dicklaxt said:
Here's the scenario.

Powerhouse, housing 13.8 Switchgear, elevated 6' above finished grade.
Okay so how do you want to run the feeder cables from the Switchgear to transformer HV chambers. This will be 3 phase 13.8KV shielded cable,the 6 transformers are 13.8-4.16 KV @ 20MVA each with a full height chamber from grade to above HV Bushings,removable door/cover.

Max feeder length to transformer #6 is 150' with 2 vertical 90's and 1 horizontal 90 when going UG,AG conduit run would probably have 2 additional 90's.Quick calcs on load at 125% is 1050 amps

Your options are :

1.Overhead in cable tray triplexed or multiconductor.

2.Rigid UG conduit with singles or multicondutor out the bottom of gear,UG encased in concrete and stubbing up into the HV chamber.

3.Direct buried cable either triplexed or multi conductors stubbing up into HV chamber using rigid conduit sleevs at both ends.

4.Overhead in rigid conduit out the bottom of bldg or thru wall,dropping down into the HV chamber.

I don't usually have these type options available as the plant specs always direct the design to be to their standards. This contract is very cost conscious and after safety and code requirements are met its potluck ,get it done, quick and cheap.The client has not specified a preference.

You as the field guy probably don't usually have this latitude either so lets make it easy on you too.

dick
Click to expand...

I would use overhead single conductors in cable tray, but would not enter the transformer chamber form the top, would use the side. That will also leave the overhead clear for transformer drop-in/removal. Segregated cable tray with barriers for 15kV/5kV/transformer alarms&fan.

U/G conduit spells trouble on the Gulf coast. I you are to chose underrgound for both primary and secondary, use reinforced ductbank.
 
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