interconnection question [RE-wrenches]

Tue Feb 22 11:27:41 PST 2005

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Hey William

Thanks for the feedback. Yes, I understand the additive effect on the buss
bars, my simple mind just has always had issues with the neutralizing effect
of the generation/load scenario.

The feeder was almost a perfect match to the load. We also have interconnect
issues, which will require me to put the lockable utility disco at the
service entrance. This will add substantially to the cost of this system due
to height restrictions and wire run length.

I don't think there will be any harmonics, but with variable frequency
drives, and non linear loads popping up all over the place, it seems highly
possible. The world is revolving around switching power supplies, but the
future will certainly see wiring repercussions for this methodology- i.e.-
doubled neutrals etc.

I thought the isolation transformer was standard fare for the industry?

Aloha

Keith Cronin
President
Island Energy Solutions Inc.
270 Kuulei Rd. Suite 106
Kailua, HI 96734
808-262-3268 Tel
808-263-0338 Fax
keith at islandenergy.net
www.islandenergy.net

-----Original Message-----
From: William Miller [mailto:wrmiller at slonet.org] 
Sent: Monday, February 21, 2005 7:14 PM
To: RE-wrenches at topica.com
Subject: Re: interconnection question [RE-wrenches]

Keith:

A couple of thoughts before I put my head cold to bed:

I assume three phase.  Sounds like 45kw may just about max out the 
feeder.  What is the feeder efficiency at max generation?  We look for 1%.

What size load center?  It needs to handle the load PLUS the generated 
power.  This is counter intuitive, but I had this explained to me by a 
licensed electrical engineer and I agreed with the concept.  It has 
something to do with overloading the buss bars on the load center with two 
sources supplying power to the loads.

What disconnecting means are required for the feeder?  If a special 
disconnect is required, it will disconnect the roof top loads.  What 
scenario would require this disconnect to be activated?  Is this going to 
be OK?

Are there harmonics generated by the roof top equipment that may mess with 
the inverters sensing circuitry?

Do you need to transformer isolate this inverter?  If so, would this be 
more appropriate installed at ground level?

William Miller

>Hey gang
>
>
>
>This might be a Bill question: (no offense to any others- I just figured he
>had the pulse of California fresh on his mind!)
>
>
>
>If you were looking at putting a 50KW system on a building, and were going
>to use a 45KW Trace unit, and they already had a 100 amp, 480 volt feeder
on
>the roof for mechanical equipment, what are the specific rules governing
the
>interconnection?
>
>
>
>My mind says, I will be basically neutralizing the load, which is connected
>to a distribution panel with a 600 amp electrical service. But, I know
>looking at this, it would seem too easy to tie in to the panel on the roof,
>and add a curb for the inverter.
>
>
>
>Thanks!
>
>
>
>Keith Cronin
>
>President
>
>Island Energy Solutions Inc.
>
>270 Kuulei Rd. Suite 106
>
>Kailua, HI 96734
>
>808-262-3268 Tel
>
>808-263-0338 Fax
>
>keith at islandenergy.net
>
>www.islandenergy.net
>
>
>
>
>
>
>
>
>[Non-text portions of this message have been removed]
>
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