Approval for grid connected 27.6KW PV system

[brent8605]

I work for a company in China, based out of Houston, TX, that is looking into the PV industry. I'm in charge of the first "scope project" here in China that will be implemented on the roof of our factory.

I haven't had any problems sourcing companies and getting all the components needed for the project, where I'm running into hardships is getting approval from the local electric company. There are many PV systems that are grid connected here in China but not in the region I'm in.

I'm looking for some brainstorming ideas on additional components I could add into the system to keep the PV system from back feeding the grid if it's down. They presented a bunch of "what if" scenarios about inverters failing, putting work crews in danger if they are in its path.

The PV system consists of right now: 120, 230W modules, 3 10KW inverters, a 30KW AC distribution cabinet and a monitoring system.

Please let me know if you have any good feedback!
Thanks.

[russ]

Hi Brent - Welcome to Solar Panel Talk!

Mike or Sunking are the best we have to comment but it seems like a local electrical engineer working with commercial electric installations will be most likely to provide an acceptable solution to your problem.

Russ

[Mike90250]

The best state of the art, current production inverters, all meet UL specs (UL17??) and have enough fail-safes that utility companies in North America and Europe approve of them.
They are the best, there are no others to be found. Look at the Xantrex ( schneider-electric.com ) gear at

http://www2.schneider-electric.com/corporate/en/products-services/renewable-energies/renewable-energies-intermediate.page?f=F13%3ARenewable%20Energies~!F23%3APhotovoltaic~!NNM1:Solar+Grid+Tie+Systems&p_function_id=15210

[Sunking]

The best state of the art, current production inverters, all meet UL specs (UL17??)

That would be UL 1741

[russ]

May well be that the guy from the local electric company wants to be made 'happy'. You can fight city hall but it is a losing battle.

The only way to resolve that is for a local guy to do what it takes - without your knowledge of course.

I spent a lifetime working in the 3rd world where those requirements are common. If your people know what they are doing you never hear about it. If you did hear about it then would be illegal.

Russ

[brent8605]

The best state of the art, current production inverters, all meet UL specs (UL17??) and have enough fail-safes that utility companies in North America and Europe approve of them.
http://www2.schneider-electric.com/c...ction_id=15210

We did not go with an inverter that is UL certified, we went with a Chint inverter that meets all certifications for China. Is there AC disconnect switches that will power off the PV system if there is no AC load from the grid feeding the distribution cabinet? If so, does anyone know the price range on these?

[Mike90250]

how big will those switches be ?? real big ones cost $$$$$

[brent8605]

I'm not sure. I'm trying to find a vendor that makes what we would need. Do you have any good sources for what I would need?

[Bala]

we went with a Chint inverter that meets all certifications for China

If the electric company does not approve of it then it would appear that it does not meet all certifications.

Perhaps instead of trying to reinvent the wheel you were to use an inverter as suggested by mike all your problems may be solved, apart from the one Russ was hinting at.

[brent8605]

If the electric company does not approve of it then it would appear that it does not meet all certifications.

Perhaps instead of trying to reinvent the wheel you were to use an inverter as suggested by mike all your problems may be solved, apart from the one Russ was hinting at.

Well when a Chinese manufacturer that makes these inverters has used these throughout mainland China in previous PV systems, it's not reinventing anything, it's going with the norm here in China..

[Bala]

The inverter you are looking at using is not acceptable to the electric company as is does not have the disconnect features required, so rather than trying to get some additional components. the breakers you mentioned, why not just use an inverter like mike posted,

That is what I meant by not reinventing, the solution is available in the inverters used in many other countries. No need to add in extra breakers etc.

[brent8605]

The big question I have now is.. Is it possible for an inverter to back feed the grid if the grid's power is off? Without power from the grid, the AC distribution cabinet will not have power, thus the inverters will not have power, so there won't be any power generated to feed anywhere, correct? When the inverters reconnect to the grid they synchronize to it and wait 5 minutes until reconnecting allowing flow back to the load.

Any thoughts or advice is greatly appreciated!

[Bala]

is it possible for an inverter to back feed the grid if the grid's power is off?

Ref post #3 from Mike,

One would have to wonder if you are serious if

A: You are still asking that question

B: That given the project you are in charge of that you have to ask that question on an internet forum.

[Mike90250]

The big question I have now is.. Is it possible for an inverter to back feed the grid if the grid's power is off? Without power from the grid, the AC distribution cabinet will not have power, thus the inverters will not have power, so there won't be any power generated to feed anywhere, correct? When the inverters reconnect to the grid they synchronize to it and wait 5 minutes until reconnecting allowing flow back to the load.

Any thoughts or advice is greatly appreciated!

Inverters with UL 1741 cert will not back feed the grid. That's what the cert is all about. They will disconnect in less than a second, and like the XW6048, would activate their internal transfer switch and supply solar power locally till the grid returns.

[john p]

BRENT8605 I think Mike has fully answered your question you are now just going round in circles..
If the inspectors need to be helped to make the approvals im sure you know how to take care of that.. As you are very well aware there are ways to get ANYTHING approved in many countries