DC-GFP/2 protection [RE-wrenches]

[Bill Brooks]

Steve:

I wholeheartedly agree that we need to have provisions for ungrounded PV
arrays in the NEC, but that does not get us out of the Ground Fault
Protection issue. On the contrary, we have to be even more diligent about
sensing Ground Faults in a floated system. Fortunately, it is easier to
sense ground faults in a floated system. The key issue is equivalent
electrical safety to grounded systems. Grounded systems definitely provide a
level of safety by referencing the system to ground potential. All the
safety benefits we get from a grounded system have to be found in an
ungrounded system. Both types of systems can be safe if designed
properly--however that is a big IF. Just ungrounding systems is not the
answer. The Europeans have been doing it safely for a very long time so it
is not like we are charting new ground here. We just need a very well
written and well substantiated section to address the issues of ungrounded
systems. It is very likely that provisions for systems above 300Vdc will
precede other ungrounded provisions.

I would be willing to bet that the SOVs have been the reason you have done
so well with your system--not the fact that you have ungrounded the system.
I really don't think you have created an unsafe situation, but it does
operate above 50 Volts, so it should either be grounded or have equivalent
grounding means.

Bill.


-----Original Message-----
From: Joel Davidson [mailto:joeldavidson at earthlink.net]
Sent: Friday, August 23, 2002 9:12 AM
To: RE-wrenches at topica.com
Subject: SPAM: Re: DC-GFP/2 protection [RE-wrenches]


Steve, Thank you for describing your well-designed system. Your experience
is
similar to old-timer wind pioneers. The National Electrical Code is
important
and necessary, but dogma requiring everyone to ground the DC negative
weakens
the Code's credibility and inhibits "out of the box" thinking. I'll bet if
Benjamin Franklin were alive, he would be experimenting with PV and wind
system
grounding instead of following someone else's rules. Franklin was an
American
Revolutionary who wasn't afraid to take risks.

"Steve Bell, Sunwize Technologies" wrote:

> Hi Joel, et al,
>
> I live out on the prairie of Illinois and we get some real wrath-of-god
> thunderstorms. I have an old long-case Jacobs on a 115' tower (tallest
> structure within several miles)as well as both a roof-mounted PV array and
a
> second array on a tracker. I float my DC wiring completely; it is totally
> ungrounded except for being connected to Delta LA302DC lightning arrestors
> installed at the base of the tower and the combiner boxes of each array.
My
> system operates at 48 VDC with dual SW (not stacked) and I sell my excess
> back to the grid.
>
> I have very good grounding on the tower (ground rods on all four guy
anchors
> and the base of the tower) and on frames and racks of the PV arrays. I
also
> use Delta LA302R arrestors on both the AC input from the grid and the AC
at
> the subpanel (AC output of the SW inverters).
>
> We have experienced some severe electrical storms that have caused
> significant damage to my neighbors electrical equipment, but I have not
had
> any damage to my equipment. The only lightning damage that I every
> experienced occurred when my system was new and the Delta arrestors were
not
> yet installed (they were on backorder). A nearby lightning strike caused a
> huge surge on the utility AC line that blew out the microprocessors of the
> SW. That was about 5 years ago. Since then, no problems.
>
> I have yet to hear a clear technical reason (not just because its code)
for
> grounding the DC conductors. I firmly believe that a floating DC system is
> both safer and less prone to lightning damage. I do believe in very good
and
> solid chassis/equipment grounds.
>
> So, I would request that the Code Review committee consider removing from
> the 2005 NEC, the requirement to ground DC systems. Or prove with solid
> technical reasons why grounding the DC wiring is requirement for safety.
If
> DC systems were allowed to be floating, we could also do away with all the
> silliness and cost and hassle of PVGFP.
>
> Okay, go ahead and blast me.
>
> Sincerely,
> Steve Bell
> Stelle, IL
> sebpv at stelle.net
>
> ----- Original Message -----
> From: "Joel Davidson" <joeldavidson at earthlink.net>
> To: <RE-wrenches at topica.com>
> Sent: Thursday, August 22, 2002 10:53 PM
> Subject: Re: DC-GFP/2 protection [RE-wrenches]
>
> > Jacobs use to float the DC negative on his wind machines to prevent
> lightning
> > damage. He grounded the tower with a ring of copper wire 10 feet out
from
> the
> > tower base buried about 18 inches to form a cone of protection. I
resisted
> > (pun?) grounding the DC negative for years, but finally gave up.
However,
> my
> > systems are almost all in regions with low lightning danger. What say
you
> guys
> > in lightning territory?
> >
>
> - - - -
> To send a message: RE-wrenches at topica.com
>
> Archive of previous messages: http://www.topica.com/lists/RE-wrenches/
>
> List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm
>
> Check out participant bios: www.mrsharkey.com/wrenches/index.html
>
> Hosted by Home Power magazine
>
> Moderator: michael.welch at homepower.com
>

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

- - - -
To send a message: RE-wrenches at topica.com

Archive of previous messages: http://www.topica.com/lists/RE-wrenches/

List rules & etiquette: http://www.mrsharkey.com/wrenches/etiquete.htm

Check out participant bios: www.mrsharkey.com/wrenches/index.html

Hosted by Home Power magazine

Moderator: michael.welch at homepower.com

==^================================================================
This email was sent to: michael.welch at homepower.com

EASY UNSUBSCRIBE click here: http://topica.com/u/?bz8Qcs.bz9JC9
Or send an email to: RE-wrenches-unsubscribe at topica.com

T O P I C A -- Register now to manage your mail!
http://www.topica.com/partner/tag02/register
==^================================================================