Multiple grid tied inverters

[poco dinero]

I presently have a Xantrex XW 6048 inverter legally tied to the grid, fed by a solar array through a 48 volt battery bank.  The 240 volt inverter output is fed to a 60 amp breaker in an electrical panel in the electrical power room in my shop building, thence to a 100 amp safety switch near the grid's meter.  I want to install a second inverter that will feed its 240 volt output to another 60 amp breaker in the same electrical panel.  The second inverter is a set of two stacked Outback GVFX 3648 inverters that are wired to put out 7200 watts at 240 volts.  My concern is twofold.

When the grid is up, will the anti-islanding features of these two different inverters interfere with each other?   

Secondly, when the grid goes down, will each of these inverters be fooled into thinking that the other inverter is the grid, and therefore not shut down like they're supposed to?

If this is a problem, would rewiring the Outbacks to feed 120 volt power to the grid instead of 240 volt power fix rthe problem?

Also, if I sent the output of the Outbacks through  a 300 foot wire run before sending it to the electrical panel would that solve the problem? 

Any help will be much appreciated.

poco

[DamonHD]

Hi,

I already have 3 grid-tie inverters connected feeding into my panel, no problem at all.  This is how they are designed to work AFAIK.

I think that they have a number of mechanisms to tell when they are really connected to the grid rather than an island of some sort, such as impedance measurement.  No confusing another weedy inverter for the big-iron grid that way, or at least not for long!

Rgds

Damon

[Ungrounded Lightning Rod]

I think that they have a number of mechanisms to tell when they are really connected to the grid rather than an island of some sort, such as impedance measurement.

I think the main triggers are frequency error and significant persistent voltage error.

The grid is VERY stable as far as frequency is concerned, while islands are not.  Voltage is not so stable but islands tend to foul that up big-time as well.

[dbcollen]

I have a Soleil2000 grid tied inverter connected to my non grid tied Outback vfx3648 inverter, and it thinks the outback is the grid. They work really well together.

Dustin

[DamonHD]

Yes, but in that case the Outback is non trying to listen to the 'grid' itself.

Rgds

Damon

[imsmooth]

I have three Sunny Boys and one Aurora that are grid tied.  No problems

[BruceDownunder]

If I were the electric power linesman's wife and kids , I would be praying that you get the authorities permission,especially now that you have breached the subject on this 'open" forum.

Every time I see an electrical linesman up near those open wires  it brings my mind to this very sort of subject.

Please ,Please get permission ,even if it costs you dollars,it may save a life or more.

Bruce

[imsmooth]

My grid-ties have anti-islanding.  When I lose power from the grid, my solar and wind go offline.  That is one of the reasons I have the shunt controller.  This way I have somewhere to dump the power.

[hydrosun]

It seems that every time someone mentions grid tie inverters someone brings up the danger of electrocuting the linesman for the utility. In this case we have someone with a legally installed inverter that has UL testing for anti- islanding. A linesman working on high voltage wires assumes it is hot and grounds the wire. This is to ensure that someone with a gas generator doesn't try to power his house without disconnecting the grid. Has anyone actually read about a linesman being injured by live wires when they were supposed to be off? There may be some but I have a suspicion that most of the hype has come in the past from electric companies not wanting to open up their distribution lines to small scale power generators. That's not how they make their profit. In the past they tried to put up as many obstacles as possible to make it hard to do. The net metering  grid intertie laws have changed but some utilities still have requirements that make it difficult.  I think it is time to look realistically at the extremely small risk of electrocution of linesmen. 
 Now a non UL listed inverter is another matter.
Chris

[JYL]

A lineman that follow the procedure will not get electrocuted.  The line is either grounded or he/she assume to work on life wire (what they are equip to do -- and what they do regularly).

Actually, the argument of many utility was:  When we ground the line, does the customer equipment will catch fire (like some generator can do).

Utility recognized anti-islanding protocol (as tested bu UL/CSA) are pretty efficient and difficult to fool.  You can have several inverter installed.  Actually, the algorithm is design to work even if several neighbor sharing a single transformer have multiple inverters.