1000 VDC PV Inverters

New inverter technology is making it very cost effective to run 1000 VDC on the PV input side of the inverter (PV source and output circuits). I know this is being done on utility scale systems "behind the fence" and in Europe (where they seem to always be one step ahead of us) but can we use in excess of 600 VDC for PV output circuits for commercial systems in the United States?
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
New inverter technology is making it very cost effective to run 1000 VDC on the PV input side of the inverter (PV source and output circuits). I know this is being done on utility scale systems "behind the fence" and in Europe (where they seem to always be one step ahead of us) but can we use in excess of 600 VDC for PV output circuits for commercial systems in the United States?
I think so. Someone will correct me if I am wrong, I am sure, but the way I interpret the 2011 NEC, the 600V rooftop maximum DC voltage for PV systems only applies to residential PV.
 

SolarPro

Senior Member
Location
Austin, TX
Yes. It is allowed under 690.7. I am aware of a couple 1,000 Vdc non-residential rooftop systems in the US. More are undoubtedly on the way. However, this probably won't become routine until NEC 2014 is adopted (assuming that the final version looks something like the draft version).

The main issues right now are limited access to listed components, more complicated AHJ approval process, and the fact that many commissioning tools are only rated for 600 Vdc. You can actually buy all of the necessary PV components certified at 1,000 volts and listed to UL Standards. But your multimeter, I-V curve tracer, etc. are probably not rated for 1,000 volts.

These limitations will become less of an issue over time. The advantages of higher utilization voltages are super compelling.
 

Besoeker

Senior Member
Location
UK
'PV' wire (a rather new specialty wire) is available in a 1000-volt rating from several suppliers. The PV wire is also Listed for installation in conduits.
Sounds like a scam to me.
1000Vdc is 1000Vdc regardless of source.
 

GoldDigger

Moderator
Staff member
Sounds like a scam to me.
1000Vdc is 1000Vdc regardless of source.
But the environment into which it is installed (full UV exposure, wet area, abrasion resistance, compatibility with standard (MC4) connectors, etc.) is not the same as other applications for 1000vDC. I think the idea was to roll all of the specifications for that use case into one primary wire type. Whether they succeeded or not is a question I will not argue. :)
One great example is that although the insulation is UV resistant, the dyes in it are not, so it is common to see nothing but black wires and white wires, some of which used to be red.:)
 

SolarPro

Senior Member
Location
Austin, TX
You wouldn't be the first to call UL a scam. But if it is a scam, it is a very official one.

Here's a link describing the design of UL compliant PV Wire:

http://www.ul.com/global/documents/offerings/industries/wireandcable/techcorner/PVWire.pdf

As explained in the document, "Both USE-2 wire and PV wire can be rated 600 V. However, PV wire can also be rated
1000 V and 2000 V to accommodate photovoltaic modules intended for use in systems with a system voltage greater than 600 V."
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
You wouldn't be the first to call UL a scam. But if it is a scam, it is a very official one.

Here's a link describing the design of UL compliant PV Wire:

http://www.ul.com/global/documents/offerings/industries/wireandcable/techcorner/PVWire.pdf

As explained in the document, "Both USE-2 wire and PV wire can be rated 600 V. However, PV wire can also be rated
1000 V and 2000 V to accommodate photovoltaic modules intended for use in systems with a system voltage greater than 600 V."
Also, the 2011 NEC (690.35(D)(3)) directs that all exposed PV source conductors in ungrounded arrays shall be PV wire .
 

tallgirl

Senior Member
One great example is that although the insulation is UV resistant, the dyes in it are not, so it is common to see nothing but black wires and white wires, some of which used to be red.:)
+1.

There are many things in the PV world that smell very much like scams, but making sure conductors survive on a roof isn't one of them.
 
Thank you!

Thank you!

Thanks folks....great information. It's been a fun day....and I think all my questions are answered. Found a great inverter/module combination. I'll be using fewer large strings, smaller wire, and saving on the racking. I'll spend a little more on PV wire, but it adds quality and is a small cost compared to all the other savings. 1000 VDC ungrounded systems are here to stay...in my opinion of course :)
 

SolarPro

Senior Member
Location
Austin, TX
Be sure to study all of the "over 600 volt" sections in the code, since your AHJ undoubtedly will refer to Article 490 and other related sections. It can get weird fast because many of these sections apply to medium-voltage systems, and 1,000 Vdc wiring methods are different that MV methods. You'll basically be using wiring methods common in 600 V systems, but with 1,000 V-rated gear; MV gear is intended for systems over 2,0001 volts. Make sure all of the BOS is certified at 1,000 volts and listed to UL 1703 or 1741. Combiners and discos should be a locking type. Last but not least, run the design by your AHJ before ordering the gear. They get the final yea or nay regardless of what the Code says.

BTW: If this is your first ungrounded PV system, this article may contain some useful info:

http://solarprofessional.com/article/?file=SP5_5_pg26_Fisher&search=
 

Besoeker

Senior Member
Location
UK
You wouldn't be the first to call UL a scam. But if it is a scam, it is a very official one.

Here's a link describing the design of UL compliant PV Wire:

http://www.ul.com/global/documents/offerings/industries/wireandcable/techcorner/PVWire.pdf

As explained in the document, "Both USE-2 wire and PV wire can be rated 600 V. However, PV wire can also be rated
1000 V and 2000 V to accommodate photovoltaic modules intended for use in systems with a system voltage greater than 600 V."
Fair point. I'm just not accustomed to dealing with cables that won't tolerate outdoor use.
 

ggunn

PE (Electrical), NABCEP certified
Location
Austin, TX, USA
Occupation
Electrical Engineer - Photovoltaic Systems
One great example is that although the insulation is UV resistant, the dyes in it are not, so it is common to see nothing but black wires and white wires, some of which used to be red.:)
Beyond that, John Wiles is of the opinion that the sun bleaching of colored insulation also reduces its flexibility and makes it brittle. He recommends using nothing but black conductors with colored tape polarity markers in sun exposed locations.
 

mike_kilroy

Senior Member
Location
United States
1140v becoming common in mining industry....

1140v becoming common in mining industry....

we are offering 1140vac 3phase input vfd's (1600vdc bus) to some large mining machinery mfgrs, as they are beginning to use 1140vac 3ph to power the mining equipment.... so you might check mining wiring and such.
 

Bigpardon

New member
Location
United States
1000V DC Listed Components

1000V DC Listed Components

It was earlier stated that whereas 1000V DC is allowed, it has difficulties due to lack of available listed components. Does anybody have a good listing or lead on 1000V UL rated components. I'm specifically looking for a DC Breaker/Contactor (1000VDC and 2500A).

Thanks
 

GoldDigger

Moderator
Staff member
It was earlier stated that whereas 1000V DC is allowed, it has difficulties due to lack of available listed components. Does anybody have a good listing or lead on 1000V UL rated components. I'm specifically looking for a DC Breaker/Contactor (1000VDC and 2500A).

Thanks
Finding a contactor with both that insulation resistance and the interrupting capability for high voltage DC at that current is going to be difficult. I would also like to see some suggestions.
Another reason for looking at bipolar arrays and the corresponding inverters.
 

texie

Senior Member
Location
Fort Collins, Colorado
Occupation
Electrician, Contractor, Inspector
Yes. It is allowed under 690.7. I am aware of a couple 1,000 Vdc non-residential rooftop systems in the US. More are undoubtedly on the way. However, this probably won't become routine until NEC 2014 is adopted (assuming that the final version looks something like the draft version).

The main issues right now are limited access to listed components, more complicated AHJ approval process, and the fact that many commissioning tools are only rated for 600 Vdc. You can actually buy all of the necessary PV components certified at 1,000 volts and listed to UL Standards. But your multimeter, I-V curve tracer, etc. are probably not rated for 1,000 volts.

These limitations will become less of an issue over time. The advantages of higher utilization voltages are super compelling.
I agree with your comments and I think we are going to see alot of changes in the future NEC cycles regarding voltages above 600 volt and not just regarding solar. After all, it was not that long ago that anything above 480 volt within buildings was not that common unless the utility controlled it. Now is is commonplace to see above 600 volt distrubution within buildings.
 

SolarPro

Senior Member
Location
Austin, TX
FWIW: the articles we were working on when I posted those earlier comments just dropped. The first article relates to the Code implications of deploying 1,000 V PV systems in non-residential applications:

http://solarprofessional.com/view/?file=SP6_3_pg22_Ball

It covers some of the Code changes that we may see in 2014.

The second article is a market survey of listed 1,000 V components (modules, inverters and combiners):

http://solarprofessional.com/view/?file=SP6_3_pg42_Brearley

It's amazing how fast we went from having access to only a few listed 1,000 V modules or inverters to a situation where manufacturers are behind the curve if they don't have a solution out yet.
 
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