grounding array/sunny boy [RE-wrenches]

[Kent Sheldon]

My opinion is to float the array. It is an easy stand to take since the
rest of the world (90%+ of the PV world market) floats the array. I
think, in many ways, grounding the array is more dangerous than floating
it. There are simple ways to detect ground faults on floated arrays
without having to detect current flow through a grounded conductor.
There is no way to fully protect against ground fault current. All you
can do is detect a problem and put out a warning.

What about the >300V battery systems? NEC does not allow them to be
grounded. And they are an infinite source of current compared to current
limited PV array. I always found this funny when installing large hybrid
systems.

Floating the array also removes the need for an AC isolation
transformer, which will improve system efficiency by 3-7% and reduce
inverter cost by 10-20%. 

There are many more benefits, but this would turn into long
dissertation.

Regards.
____________________________________________
Kent Sheldon
Manager, Industrial Power Systems
SMA America
925 513 8813 Brentwood Office (Primary)
530 273 4848 Grass Valley Office

-----Original Message-----
From: Windy Dankoff, Dankoff Solar [mailto:windy at dankoffsolar.com] 
Sent: Sunday, January 13, 2002 12:37 PM
To: RE-wrenches at topica.com
Subject: RE: grounding array/sunny boy [RE-wrenches]

>Marco, when I refer to 'grounding the array' I am referring to PV 
>electrical grounding. This is the grounding of the + or - PV 
>conductor. In most (99.9%) US installations the negative conductor 
>this is grounded at/within the inverter. .....     There is much 
>debate over this subject, as the US is the only country that feels 
>it is necessary to electrically ground the array.
>...
>
>Kent Sheldon
>Manager, Industrial Power Systems
>SMA America


Kent,

If you don't mind, what is your opinion on the matter? Would you 
rather see the PV + and - "floating" (ungrounded). That technique is 
preferred in telecom, I've heard, to reduce incidence of lightning 
related damage. It is also what we recommend in solar water pumps, 
and it makes good sense to me, and many others have expressed this 
opinion regarding wind systems etc.

Is this an NEC issue that we should try to change?

Thanks,

Windy

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