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New Grid Tie system


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Good day,

 

I am Erastus living in Melkbos (West Coast). I an new to solar and stuff. I wonder if you guys can please direct me where I can get the requirements for disconnecting a grid tie system when there is a network fault.
Also how to determine there is a 220V "missing" fault

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10 hours ago, Erastus said:

Is is based on load or voltage drop?

I will try and explain it as nicely as @plonkster normally does. Normally a GTI will inject a pulse into the Grid to try and push it "Out of phase". This pulse is absorbed by the grid. Once the grid falls away, the pulse will increase in amplitude and this condition will be detected by the GTI and the GTI will disconnect from the grid and continue to supply the loads. Once GTI senses that the Grid is back for a certain time depending on the inverter, It will close the Grid-Relay and reconnect to the Grid.  

Plonksters explanation has some more detail and came with a video, I just cant find the link right now. 

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2 minutes ago, Jaco de Jongh said:

I will try and explain it as nicely as @plonkster normally does.

Nice! And a lot more concise!

The video is of an ABB inverter connected to the output of a Multiplus. It demonstrates a second way of detecting a grid outage, which is to inject a small disturbance (the other is to attempt to shift the frequency). Because the Multiplus isn't quite as good at absorbing this disturbance as the big bad grid is, you get to pick it up with an oscilloscope.

 

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19 minutes ago, Jaco de Jongh said:

I will try and explain it as nicely as @plonkster normally does. Normally a GTI will inject a pulse into the Grid to try and push it "Out of phase". This pulse is absorbed by the grid. Once the grid falls away, the pulse will increase in amplitude and this condition will be detected by the GTI and the GTI will disconnect from the grid and continue to supply the loads. Once GTI senses that the Grid is back for a certain time depending on the inverter, It will close the Grid-Relay and reconnect to the Grid.  

Plonksters explanation has some more detail and came with a video, I just cant find the link right now. 

Tnx I know a little about protection e\and electronics did not realize they are using phase detection at this level. One thing that concerns me is I read that relays is not an acceptable method to isolate a grid tied system. Is that a fair view on it. The old argument burned contacts. I been looking for the "rules" on this as I was under the impression that a motorized  mini breaker is required.
If I am talking to much tell me to keep quite I don't mind

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28 minutes ago, Erastus said:

One thing that concerns me is I read that relays is not an acceptable method to isolate a grid tied system. Is that a fair view on it.

This can also become a lengthy discussion. If your Inverter is on the list of aproved Inverters, then it would mean that the relay/software combination was tested and found to be functioning correctly to offer adaquate  protection. The best device (Zeigler - not sure about spelling)  rely on  two Contactors to ensure effective disconnecting from the grid, so the relay/contactor will  always be part of an accepted disconnecting method. 

https://www.greencape.co.za/assets/Uploads/Approved-Photovoltaic-PV-Inverter-List.pdf

 

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2 minutes ago, Jaco de Jongh said:

This can also become a lengthy discussion. If your Inverter is on the list of acceptable Inverters, then it would mean that the relay/software combination was tested and found to be functioning correctly to offer adaquate  protection. The best device (Zeigler - not sure about spelling)  rely on  two Contactors to ensure effective disconnecting from the grid, so the relay/contactor will  always be part of an accepted disconnecting method. 

https://www.greencape.co.za/assets/Uploads/Approved-Photovoltaic-PV-Inverter-List.pdf

 

Thanks Jaco,

I am only trying to understand stuff not trying to argue stuff.

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12 minutes ago, Erastus said:

I am only trying to understand stuff not trying to argue stuff

What I could gather from post, long ago, and if my memory serves me well. Relays alone and software alone (Related to Grid feedback) is not seen as acceptable ways, but a combination of the two is acceptable. 

 

41 minutes ago, Erastus said:

The old argument burned contacts.

I guess that is why they want two, If the one burns the second one will break the circuit. We also apply a similar technique on some of our critical equipment at work. I can relate to your concern

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39 minutes ago, Erastus said:

relays is not an acceptable method to isolate a grid tied system

The old method where the relay is powered by the grid and should drop out if the grid fails, is not sufficient, for the simple reason that if something goes wrong and the inverter does backfeed into the grid, it might backfeed enough to power the relay/contactor that is supposed to stop this. So you are quite right: it is not sufficient.

One might argue that it is unlikely that the inverter would feed back in such a manner, but if that is true, then why do you need the contactor in the first place? :-)

41 minutes ago, Erastus said:

burned contacts

Welded contacts more precisely. That's why they require an interlocked (mechanically or otherwise) switch. If a contact gets welded, it should provide signaling feedback in such a manner that the other source cannot engage. A normal contact on its own doesn't do that either.

44 minutes ago, Jaco de Jongh said:

Zeigler - not sure about spelling

The exact device is the Ziehl UFR1001e. I tend to remember it because the German word Ziel (almost spelled the same) means goal or target. Pretty sure that has nothing to do with it, but that is how I remember it. It has two passive monitoring circuits controlling two contactors, and they also monitor each other for backup. You don't have to use both contactors though. In a Victron setup you only need to use one, because there is already another one inside the Multi.

This is a passive anti-islanding device. If things go out of bounds, or if they shift too quickly (eg RoCoF, rate of change of frequency), it disconnects. Our regulations require that the inverter must implement at least one active measure (ie a deliberate attempt to destabilise one of the parameters the Ziehl watches) in order to be acceptable.

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17 minutes ago, plonkster said:

The old method where the relay is powered by the grid and should drop out if the grid fails, is not sufficient, for the simple reason that if something goes wrong and the inverter does backfeed into the grid, it might backfeed enough to power the relay/contactor that is supposed to stop this. So you are quite right: it is not sufficient.

One might argue that it is unlikely that the inverter would feed back in such a manner, but if that is true, then why do you need the contactor in the first place? :-)

Welded contacts more precisely. That's why they require an interlocked (mechanically or otherwise) switch. If a contact gets welded, it should provide signaling feedback in such a manner that the other source cannot engage. A normal contact on its own doesn't do that either.

The exact device is the Ziehl UFR1001e. I tend to remember it because the German word Ziel (almost spelled the same) means goal or target. Pretty sure that has nothing to do with it, but that is how I remember it. It has two passive monitoring circuits controlling two contactors, and they also monitor each other for backup. You don't have to use both contactors though. In a Victron setup you only need to use one, because there is already another one inside the Multi.

This is a passive anti-islanding device. If things go out of bounds, or if they shift too quickly (eg RoCoF, rate of change of frequency), it disconnects. Our regulations require that the inverter must implement at least one active measure (ie a deliberate attempt to destabilise one of the parameters the Ziehl watches) in order to be acceptable.

Just for the record I speak my two tales deliciously. Thanks for the feedback appreciated.

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1 hour ago, Erastus said:

One thing that concerns me is I read that relays is not an acceptable method to isolate a grid tied system. Is that a fair view on it.

My 2012 design Interlock was deemend as off-grid by multiple Sparkies and a Engineer, to be seen as off-grid, never the twain shall meet.

Today you get relays and double pole switches that Spakies mount inside the DB board to do the exact same thing, installed and signed off with a CoC.

If ever you have any doubt, speak to Sparkies that install UPS'es / Generators that are connected to a DB boards. There is no misunderstandings nor interpretations that I could pick up in asking a few the same question i.e. the way to do it is set in stone - that is for the experienced ones.

That the DB board split will cost a few rands to meet all the regs. There are alternative plan like a surface mounted DB board to power the selected circuits. Easier, simpler and the preferred method than re-arranging and splitting a existing DB board.

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24 minutes ago, Erastus said:

Is it allowed to do it at the metering box?

You know of any one that can assist?

Where can I see/get your design?

It is all here: Off Grid with Eskom as Backup

I am now moving to a Victron Multigrid, just need to train the Sparkies, with Plonksters help, to connect it right. :-)

Why?
Because I will save much more (no wastage waiting for the SOC to be reached),
On cloudy days all the power goes to the house, offsetting the Eskom usage, even if it is 100watts. Therein the better savings over time.
Batteries are used better therefor lasts longer with the ESS software from Victron,
And being grid tied with CoC and Engineer cost where "cheaper" when compared against the wastage and CoC of my old setup.

PM me and I can give you some Sparkies I liked here in Cpt.

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2 minutes ago, The Terrible Triplett said:

It is all here: Off Grid with Eskom as Backup

I am now moving to a Victron Multigrid, just need to train the Sparkies, with Plonksters help, to connect it right. :-)

Why?
Because I will save much more (no wastage waiting for the SOC to be reached),
On cloudy days all the power goes to the house, offsetting the Eskom usage, even if it is 100watts. Therein the better savings over time.
Batteries are used better therefor lasts longer with the ESS software from Victron,
And being grid tied with CoC and Engineer cost where "cheaper" when compared against the wastage and CoC of my old setup.

PM me and I can give you some Sparkies I liked here in Cpt.

Will do many thanks for your help

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