[RE-wrenches] 3-phase wire run considerations

[Darryl Thayer]

y seem to be on top of the situation.  I would use the MPPT wattage of the array for my source wattage.  devide by 480 volts and 1.73 for three phase and you have the current per leg.to do your voltage drop calcs from.   IO have not always been carefull to keep similar phases apart, but you will probibly buy your direct burrial in the form of triplex so lay them like you buy them.  Of course do not runn through metal holes unless balanced currents.  Also any time you make a short run, KEEP the length the same.  
 
DT 


________________________________
From: Luke Christy <sgsrenewables at gmail.com>
To: re-wrenches at lists.re-wrenches.org
Sent: Wednesday, November 16, 2011 9:51 PM
Subject: [RE-wrenches] 3-phase wire run considerations


Hi Folks,
In several months we will be installing a 100kW ground mounted PV system for one of our commercial customers. I'm in the planning stage and am looking at the wire runs. The site requires a 700' underground wire run between the 480V service and the single central inverter located at the array (a PVP100kW unit). I have two related questions: 
1: Given the significant cost of the AC cabling for this situation, what is the most appropriate number to use for current in running voltage drop calcs? The wiring is going to be significantly oversized to achieve a ~1% VD at this length. I could use the max rated output current of the inverter (120A), but that seems like it might be overly conservative. Opinions?

2: It looks like the most cost effective and manageable solution for this run will involve several paralleled sets of cables. How important are the considerations of careful cable bundling? ie: putting several conductors per phase willy nilly in a trench vs having separate triplexed bundles.

Thanks in advance for your thoughts.


  

Luke Christy 

>NABCEP Certified PV Installer™: Certification #031409-25 (Luke Christy)
NABCEP Certified Solar Thermal Installer™: Certification #ST032611-03    
> CoSEIA Certified PV Installer (Luke Christy)
>
>Solar Gain Services, LLC
>Monte Vista, CO.
>SGSRenewables at Gmail.com

>





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