[RE-wrenches] anti islanding?

Wed Feb 17 17:40:05 PST 2010

I have been told by SMA to connect the inverter upstream (utility side) 

 of the ATS if it is feasable.

-----Original Message-----
From: re-wrenches-bounces at lists.re-wrenches.org
[mailto:re-wrenches-bounces at lists.re-wrenches.org] On Behalf Of jay peltz
Sent: Monday, February 15, 2010 10:42 AM
To: RE-wrenches
Subject: Re: [RE-wrenches] anti islanding?

Hi Nick, 

The usual answer is this is  a bad idea for the generator.
The only exceptions  I know of are if the solar is a small percentage of the
generator size, then its "probably" OK on the generator.

jay 
peltz power

On Feb 15, 2010, at 7:27 AM, Nick Soleil wrote:

I have a couple of projects  coming up, which will require additional work
to prevent connecting to a Generac Guardian's ATS panels.  Do the same
concerns still exist regarding back-feeding an inverter to a generator
panel?  Can the inverter damage the generator?  I know this was the cases,
at least theoretically.  Should I continue to be concerned?

Nick Soleil
Project Manager
Advanced Alternative Energy Solutions, LLC
PO Box 657
Petaluma, CA 94953
Cell: 707-321-2937
Office: 707-789-9537
Fax: 707-769-9037 

  _____  

From: Darryl Thayer <daryl_solar at yahoo.com>
To: RE-wrenches <re-wrenches at lists.re-wrenches.org>
Sent: Sat, February 13, 2010 5:51:33 PM
Subject: Re: [RE-wrenches] anti islanding?

Hi August
I felt I was a little to cryptic in my answer, so here is a longer answer.

The inverter always tries to increase the frequency if it is connected to a
grid, it could never speed up all those billions of tons of rotating
equipment, so the frequency stays the same.  If two inverters see themselves
they will both try to increase the frequency, they will succeed and if the
frequency is greater than the 60.5 HZ the inverter shuts off.  If there is a
load that can stabilize frequency such as a synchronous motor they will
either speed up the motor or they will not be able and the motor will slow
down.  Either way the frequency changes and the inverter shuts down for
frequency out of specification which is <60.5 or >59.3 else the inverter
shuts down.  

The inverter also looks at a voltage, and to sell power it wants to raise
voltage, necessary to put power into the grid.  Unless the load exactly
matches the inverter power the voltage will rise or fall if the load is to
large and it will fall out of voltage specification shutting the inverter
down.  

One Last feature, the inverter is voltage commutated, and it looks for
voltage to add its power to. if you had purely a resistive load, both
inverters would wait for the voltage from the other inverter, and nothing
would get done.    

Think of it this way, for the system to last for 10 seconds, the speed of
this strange device (synchronus motor) cannot change speed more than 0.5%
per 10 second and it would coast for 30 minutes before stopping, and this
motor would have to be doing no work. 

--- On Sat, 2/13/10, August Goers <august at luminalt.com> wrote:

> From: August Goers <august at luminalt.com>
> Subject: [RE-wrenches]  anti islanding?
> To: "RE-wrenches" <re-wrenches at lists.re-wrenches.org>
> Date: Saturday, February 13, 2010, 10:29 AM
> Hi Wrenches,
> 
> Does anyone know where I can go to read about general
> information on how grid tied inver anti islanding works? I'd
> like to be able to describe this in better detail to our
> tech-savvy clients. 
> 
> Thanks,
> 
> August
> 
> 
> August Goers
> 
> Luminalt Energy Corporation
> O: 415.564.7652
> M: 415.559.1525
> F: 650.244.9167
> www.luminalt.com
> _______________________________________________
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