Long Large Feeder calculation

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sparkyguy545

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Note: Possibly should be in Engineering Section

Conditions:
Buried existing conduit: 2ea 5" RMC.
Assume no add'l temperature derating necessary (30?C amb.)
Requirement:
Install 600 A Feeder in existing conduits (handholes for pulling will be added as a separate issue)
Conductors will be 90?C rated wet and dry, likely XHHW-2, or RHW-2
Termination lugs at end will be rated 75?C
Distance 1800 feet
Allow Maximum 3% VD
System" 480 V, 3-phase, 3-wire plus supplemental equipment gnd cond. (no neutral).

Comp assistance for feeders and EGC including allowances for VD.
I've done this two ways, and get two different answers for cable make-up.
Before it's suggested, the project space at the ends does not allow step-up, step-down xfmrs. I'm stuck with the 5" pipe.
 
Take a look at two sets of 600kcmil in each raceway along with an EGC. Without doing the calcs, I think the EGC would be a 300kcmil in each raceway. The 5" will fit nine 600kcmil XHHW so you should be good to go. The calculator I use shows this set up with a 3% drop with a 600 amp load and 1800'. It doesn't really let me enter 2400kcmil as the conductor size so I use a load of 150 amps for one 600kcmil.
 
From the data you presented, the voltage drop formula for your 3-phase circuit requires that you install 2,753,880 CM aluminum conductors per phase:
CM=1.732(1800)(600)(21.2)/(.03)(480).

This could be accomplished by installing one of three variations:
1. (2) sets of 1500 kcmil (one set per conduit plus EGC) , but this size is probably unavailable.
2. (4) sets of 700kcmil (two sets per conduit plus EGC). Current cost for 700kcmil is $1.71 per ft., but availability may be an issue.
3. (6) sets of 500 kcmil (three sets per conduit plus EGC). Current cost for 500kcmil is $1.17 per ft. Assuming that the EGC is 500kcmil, Table C.8(A) indicates that Type RMC will accomodate the ten conductors. This option may be the best solution.

Regardless of whichever variation is chosen, you will possibly have to deal with wire bending space and termination lug sizes at each end of the 1800 ft. run.
 
kevin said:
From the data you presented, the voltage drop formula for your 3-phase circuit requires that you install 2,753,880 CM aluminum conductors per phase:
CM=1.732(1800)(600)(21.2)/(.03)(480).

This could be accomplished by installing one of three variations:
1. (2) sets of 1500 kcmil (one set per conduit plus EGC) , but this size is probably unavailable.
2. (4) sets of 700kcmil (two sets per conduit plus EGC). Current cost for 700kcmil is $1.71 per ft., but availability may be an issue.
3. (6) sets of 500 kcmil (three sets per conduit plus EGC). Current cost for 500kcmil is $1.17 per ft. Assuming that the EGC is 500kcmil, Table C.8(A) indicates that Type RMC will accomodate the ten conductors. This option may be the best solution.

Regardless of whichever variation is chosen, you will possibly have to deal with wire bending space and termination lug sizes at each end of the 1800 ft. run.
Click to expand...




I'd like to one thing, where can you get wire that cheap? The last 600 cu I bought was 4 times that cost
 
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