Extreme distance voltage drops

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tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
I would go with solar if it is possible. Did you say what the load is?

If solar wont work can you use Chaper 9 Table 8 note2 to calculate a multiplier for K to use the actual soil temp at 2 Ft or whatever your depth is?
My guess is you would have 18° C or a k= 10.5 for copper or 17.2 for aluminum.

If your load is around 1000VA for eaxmple
#4 AL USE/XHHW-2 Aluminum @6500 FT with a K =17.2 would be around 468V

For medium sized loads like 7-12kw you could use a 1000V nominal system and PV wire:
http://hvac.southwire.com/wp-conten...OVOLTAIC-WIRE-1000-VOLT-TYPE-RPVU-–-BLACK.pdf
I am looking into that for water pumping on a large farm now.
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Yes very important. Not panel size, not breaker size, not article 220 load, preferably not even nameplate load - ACTUAL load.

I am guessing the actual load for something like this is quite small, but being a roadway project, there are probably many people willing to waste lots of money.


I wouldn't be worried about voltage drop. I'd be worried about someone getting killed or injured from a breaker that does not trip. Breaker size is the governing factor here.
 
For medium sized loads like 7-12kw you could use a 1000V nominal system and PV wire:
http://hvac.southwire.com/wp-content/uploads/2017/03/PV-PHOTOVOLTAIC-WIRE-1000-VOLT-TYPE-RPVU-–-BLACK.pdf
I am looking into that for water pumping on a large farm now.

I know you are familiar with my 2.4kv system I mentioned here because you replied: https://forums.mikeholt.com/threads/my-solar-system.148865/ but for others reading this: PV wire goes up to 2KV, which is of course better for wire size/VD issues, but the issue with going above 1kv is then the installation would have to fall under 300.50(A)(3) which requires RGC/IMC or PVC encased in concrete which may very well make it a deal breaker. The NEC is not very friendly to unshielded cables.
 

tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
Whats the best practice for ensuring the OCPD works for a long run like that? Since the OP is gone for now lets say the load is 1kw @ 6500 FT
 

mbrooke

Batteries Included
Location
United States
Occupation
Technician
Lived it.

Not everyone does. The thing that gets my panties in a bunch is the CMPs know it, and instead of making a simple rule limiting how far a any particular wire gauge can travel they're slowly mandating various GFCIs and "special circuit protectors" which is great for manufacters but not how you would go about fixing a loop hole in the code.
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
My point
Whats the best practice for ensuring the OCPD works for a long run like that? Since the OP is gone for now lets say the load is 1kw @ 6500 FT
For Short Circuit Analysis of 1kw / 277vac / 1.732, my point-to-point SCA shows ~41 Amps, which trips 20A breaker on #8, 6500 ft away, 2.9%vd.

Setting power factor to 85% matches "C" table results, published by IEEE Std. 241-1990, IEEE Recommended Practice for Commercial Power Systems.

Overload protection should be integrated within fused utilization equipment.
 
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tortuga

Code Historian
Location
Oregon
Occupation
Electrical Design
My point

For Short Circuit Analysis of 1kw / 277vac / 1.732, my point-to-point SCA shows ~41 Amps, which trips 15A breaker on #8, 6500 ft away, 2.9%vd.

Setting power factor to 85% matches "C" table results, published by IEEE Std. 241-1990, IEEE Recommended Practice for Commercial Power Systems.

Overload protection should be integrated within fused utilization equipment.
Interesting thanks! 277 is L to G fault probably worst case?
 

ramsy

Roger Ruhle dba NoFixNoPay
Location
LA basin, CA
Occupation
Service Electrician 2020 NEC
Tried it on an iPhone app, selected 480vac L-L, 75 kva xfmr 1%Z, 6500ft of #8, got SCA of 66 Amps.
EATON Bussman series FC2 fault current calculator
 
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