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City of Cape Town Legalities around grid tied systems


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@plonkster, thanks for kick-starting my brain again, Ive been out of the electrical field for too long and although I know the answer, i find it very difficult to explain. 

17 hours ago, plonkster said:

The scary stuff starts when you have two guys in the same neighborhood on the same phase both feeding back

You had me wondering about this for a moment, and for that moment I thought it might actually be possible, although in the back of my mind I knew it is not. That is why I was willing to do the test with my two inverters, to prove the theory wrong.  

Ill start by saying this again. 

20 hours ago, Jaco de Jongh said:

Grid feedback is not an output like the output of an inverter or a the output of a generator

 

20 hours ago, Jaco de Jongh said:

Grid feedback is a synchronization function, but for it to be able to push current back The GTI needs some kind of carrier, which happens to be the supply voltage

1: The only time your GTI will create voltage is when the grid is not available, it will use the available PV or Battery and convert it to AC on its own OUTPUT side. 

2: When grid is available, the GTI will latch unto the grid voltage and "Generate" CURRENT into the existing Grid Voltage.

3: When Exporting the same as in 2 will happen and CURRENT will be pushed back in the grid using the GRID Voltage as a carrier. It does not generate its own voltage and push that back into the grid, it pushes current back.

17 hours ago, plonkster said:

When those two inverters find each other

 This can not happen, because when the grid fails the "carrier" is gone, and with only pushing current back, their will be no way of finding each other and the whole network will collapse. There will be no more voltage to push current back unto and a GTI does not generate Voltage on its feed side. 

I did run this past 2 of our electrical engineers on the mine and told them that I have difficulty explaining it. One of them offered to find the right word or way to explain it better. 

I stick to my point that GTI's, connected correctly, is much safer than most people think they are!

I wish I had the right words and knew the correct way to explain this. 

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@Jaco de Jongh why don't you contact CoCT and ask them about why they are worried and ar warning people as per their newsletter?

Have sent you a PM with the contact person. 

For I think, if one understands more, as you, the questions to them can be better formulated.

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On 11/15/2016 at 9:06 AM, The Terrible Triplett said:

To note, why not to do it illegally, is: It has come to the attention of the City of Cape Town that certain rooftop PV systems are being poorly installed while others are being connected to the electricity grid illegally. These incidents are a safety concern for three reasons:

Dont need to contact them, they clearly state what they are concerned about, and they are talking about incorrect or illegal connections and some forum members think that connecting a GTI is illegal. It is illegal where there is already rules in place. but how can something be illegal if their is no laws or regulations against it in other City's.

That is why i feel, we take a document talking about real illegal or incorrect installations (With safety issues) and we want to waive it in front of other peoples noses because we feel they have illegally connected to the grid. You don't care if all safety precautions have been met, for you it means that if they guy doesn't have a approval letter, it is illegal.   

In Capetown yes, connecting without an approval letter is illegal, in Phalaborwa their is nothing preventing me from doing so. Only once the bylaws state I need a approval letter, can my installation be seen as illegal.

I hope you will drop this witch hunt soon. Dont confuse real problems with your own perception of what is legal and what is not and then think it is because a GTI is unsafe. Anything safe in the world applied or used wrongly becomes unsafe. 

I am merely trying to point out that a GTI used and installed correctly is much safer than people want to make it out to be.

I see where you are coming from, but its time to see where we are coming from, Your hometown laws will reach us sooner or later and then we have to prove if our installation meets the  criteria. Until then there is not much I can do but wait.  

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32 minutes ago, Jaco de Jongh said:

This can not happen, because when the grid fails the "carrier" is gone

Oh it can and it will :-) Of course the circumstances has to be just right and the likelihood is incredibly small, but lets say you live in a cul-de-sac with 6 houses and its just you and the guy three houses down on the same phase, both of you feeding back. It is conceivable that your inverter might tie with his and his inverter with yours. You will also end up partially energising the transformer in the street.

But note that as I indicated earlier this happens only when there is either no anti-islanding OR you have passive measures only and things are 100% balanced... which is also unlikely. I just think the supplier would prefer that call to be made by experts instead of your average cowboy who plugs in a GTI using a normal 230VAC socket! (see earlier picture) :-)

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7 minutes ago, plonkster said:

Oh it can and it will :-)

Okay, lets say you are right, can you pleas answer a few simple questions. 

  1. What does the GTI need to sync to?
  2. After syncing, what is pushed back into the grid. (Please remember, export is not an output) 
  3. Once the grid fails, what will be left for the other inverter to find mine?
  4. Will my inverters current find my neighbor's current and then magically change their inputs to outputs, start to generate voltage and then get the grid back up and running, supporting each other all the way?  

Plonk I really believe that it is not possible. I respect your thoughts that it is, but would love to see the prove.  

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6 minutes ago, Jaco de Jongh said:

What does the GTI need to sync to?

There are two copper wires between your house and the fictitious neighbour with the badly configured inverter (or perhaps he's running a biogas synchronous generator!). That is all that is needed to carry enough voltage with a trickle of current and provide something to sync with UNDER CERTAIN PRECISE CONDITIONS (let me stress that). The point is to make the probability as low as possible, aka make the NDZ as small as possible.

8 minutes ago, Jaco de Jongh said:

After syncing, what is pushed back into the grid.

The precise conditions in my example includes an accidental exact balance where between yourself and the neighbour you use all the power that's being pushed back (or perhaps he has a grid limiter that keeps his side at zero and so do you... so you push back just enough to keep each other online :-P).

9 minutes ago, Jaco de Jongh said:

Once the grid fails, what will be left for the other inverter to find mine?

Two thick copper wires.

10 minutes ago, Jaco de Jongh said:

Will my inverters current find my neighbor's current and then magically change their inputs to outputs, start to generate voltage and then get the grid back up and running, supporting each other all the way?  

Hybrid inverters push back via their inputs, so no swapping is required.

Let me stress again, it is incredibly unlikely to happen with just one or two embedded generators. The issue the supplier has to deal with is what you do when it becomes common.

Then again, Wikipedia seems to note that there are questions about whether the problem really requires all the effort spent on it. So really, my point is academic at best. In practice you are most likely right. You just won't get away with it when the council guys show up though :-)

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5 minutes ago, Jaco de Jongh said:

There is still no voltage.

There is voltage. It's two thick copper wires, getting a voltage on to them is easy (once again, given the specific circumstances where there is either no load or you have the power to carry them).

An embedded generator is capable of energising the line. Inverters aren't the only kind either. In general the combined load of all the houses on that phase is such that your little generator has no hope of powering them all. This causes a massive voltage drop on the input side of your inverter and it immediately drops into UPS mode and de-energises the input side.

The question you have to deal with is what happens if you have enough power to hold it up (hence my example of a two-house island) and you have another generator on the other end of the wire doing the same thing.

There is also another side to this: Intentional islanding. Some systems are set up to intentionally create an island. Those systems still have to isolate themselves from the grid when they do so (and safely rejoin later). If they are misconfigured, and it is a big building with a couple hundred kilowatt of PV, things can get interesting.

I think there is two sides to this story. Do you, as a responsible home owner have to worry about this? Probably not, the odds are incredibly low that one little 5kva GTI will have the capability to do this. In the Wikipedia article they say chances of a line worker being hurt is less than one in a million in any given year. BUT... do you as a council just want to throw the doors open and let anybody connect anything? Probably not :-)

Didn't someone here already tell us how a wind farm somewhere in the country ended up energising lines it should not have? Wind Farms are supposed to shut down if the grid goes down.

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11 minutes ago, plonkster said:

There is voltage. It's two thick copper wires, getting a voltage on to them is easy

And where does that voltage come from? It comes from the grid, not from your GTi, your GTi just syncs to it and pushes current into it. I really don't know how to get you to understand it. Once the Grid voltage is gone, you are left with the wires only and current can not flow though the wire without the voltage percent. Power is a product of Voltage and Current flowing through the conductor, all three are needed for the network to function. If you take the voltage away the gti will and can not take the place of the grid, it does not supply the voltage to the grid, the voltage comes from Eskom.

 

39 minutes ago, plonkster said:

Hybrid inverters push back via their inputs, so no swapping is required.

That is my point exactly, hybrids push current back through their inputs not voltage, if you need the voltage for the other inverter to sync to , the input and output should swap around otherwise there will be no voltage and consequently no syncing or seeing each other.

42 minutes ago, plonkster said:

with the badly configured inverter (or perhaps he's running a biogas synchronous generator!).

 

22 minutes ago, plonkster said:

Didn't someone here already tell us how a wind farm somewhere in the country ended up energising lines it should not have? Wind Farms are supposed to shut down if the grid goes down.

Now we are moving away from the original problem, Can two or more GTi's maintain each other should the grid fall away while they are exporting (CURRRENT)

My answer remains no, till proven wrong.

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3 hours ago, Jaco de Jongh said:

I hope you will drop this witch hunt soon.

Noted.

I will stop pointing out to be mindful as there is legislation in place that may flow over to other areas.

As far as THIS thread is concerned, it is about CoCT, so a witch hunt here is allowed. :P

The wind farm, it was me. My pal lost a few devices because they did not stop feeding back with power failures. He accidently saw the volts one day when the power was "off". Was up and down like as low as 110v, jumping around, devices going on and off. He lost 2 fridges, 1 PC and screens. All where replaced under his insurance.

 

Seriously though.
There are brokers on this forum, but they will never advise or openly discuss matters on their industry here.
There are installers here, who are also do not like getting involved with GTI advice I have picked up.
And I presume there are qualified electricians here, whom also are not saying a word.

Why? As professional people they steer clear of saying too much on a open forum.

I just think grid tie must be thoroughly researched and understood, and not rely in Wikipedia or experimentation to prove / disprove a point on a open forum.

 

Any case, that's me on this subject of GTI. Ye all do as you please, as is your right, but IF Plonk is right and I lose equipment as per his scenario, or a wind farm feeding back when it should not, I will find them arses and give them a good kicking. :D

Do it right, the professional way, or don't do it at all.

Over and out.

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26 minutes ago, The Terrible Triplett said:

There are installers here, who are also do not like getting involved with GTI advice I have picked up.
And I presume there are qualified electricians here, whom also are not saying a word.

Why? As professional people they steer clear of saying too much on a open forum.

I just think grid tie must be thoroughly researched and understood, and not rely in Wikipedia or experimentation to prove / disprove a point on a open forum.

Any advice on where to find a "Closed forum" to solve disputes like this, where experiments on all types of equipment (To obtain answers) is allowed. One where qualified and professional people wont withhold valuable info from the public. One were we can do our tests and then report back to the public here. I would like to be part of such a forum.

When I joined this one I thought it happens here, doing all kind of tests and experiments and together finding answers to the questions stuck in all newcomers minds, mine included. So much to share and learn, whats the use of choosing to keep quite then.? Its fine to test how much power a 10Watt LED really uses, or how much power my panels can give under certain conditions, just don't test if inverters can really keep each other going, we don't really need to know if its possible, using the possibility to scare the public does carry more weight than proving the theory wrong, if i understand you correctly?

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59 minutes ago, Jaco de Jongh said:

And where does that voltage come from? It comes from the grid, not from your GTi, your GTi just syncs to it and pushes current into it.

It depends on the impedance of the grid connection. The usual outage, where your grid connection is still connected to a transformer winding on the other end, has a low impedance and the outage will create a voltage drop, a shift vector, a frequency shift, just about every islanding signal in the book! But it is in theory possible, for a different kind of high impedance outage (gardener severs the cable somehow without shorting it out) where the embedded generator will see it's own voltage reflected back. If it is very stable, it could essentially follow itself. Like I said, this only happens under very specific conditions, conditions which define a so-called Non-Detection Zone. Lots of academic papers on the subject. There really is no way to know how a collection of Embedded generators will behave unless you set down some kind of standard.

I hope that makes it clear :-)

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30 minutes ago, plonkster said:

There really is no way to know how a collection of Embedded generators will behave unless you set down some kind of standard.

Then I take that as the final answer, I am sure CoCT is aware of the possibility of this and are willing to take the risk of that exact special moment, and the dangers it might subject  their staff to. it was all taken into consideration, when they issue the approval letter to install these devices. If they are happy taking the risk, I am happy as well and will follow their example and guidelines.  

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38 minutes ago, Jaco de Jongh said:

If they are happy taking the risk,

Just found this, might explain why they still allow the installation of these units despite of the risk involved. 

https://en.wikipedia.org/wiki/Islanding#Negative-sequence_current_injection

 

Quote

Given the activity in the field, and the large variety of methods that have been developed to detect islanding, it is important to consider whether or not the problem actually demands the amount of effort being expended. Generally speaking, the reasons for anti-islanding are given as (in no particular order):[2][3]

  1. Safety concerns: if an island forms, repair crews may be faced with unexpected live wires
Quote

The first issue has been widely dismissed by many in the power industry. Line workers are already constantly exposed to unexpectedly live wires in the course of normal events (i.e. is a house blacked out because it has no power, or because they pulled the main breaker inside?). Normal operating procedures under hot-line rules or dead-line rules require line workers to test for power as a matter of course, and it has been calculated that active islands would add a negligible risk.[4] However, other emergency workers may not have time to do a line check, and these issues have been extensively explored using risk-analysis tools. A UK-based study concluded that "The risk of electric shock associated with islanding of PV systems under worst-case PV penetration scenarios to both network operators and customers is typically <10−9 per year."[5]

With the risk of people getting hurt being smaller than 0.000000001 per year, I think its safe to approve such installations. (Just an answer to my own statement above)

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Hang on, we're missing each other. The context here is the claim that just connecting any old grid-tie inverter to the grid might be a bad thing, hence the list of approved inverters. The approved inverters go to great lengths to ensure that the NDZ I keep referring to is almost non-existent -- to the point that it is questionable if the expense they go to is really worth it. If you have any of those inverters there is no need to worry. There is no danger if you have an approved inverter.

If you don't have such an inverter, then you might be able to get away with just a grid-powered contactor, and in 99% of cases it will work fine precisely because your small inverter cannot power the whole neighbourhood. But that one corner case... that one time the outage is out of the ordinary... then you really want the one with all the nice standards compliance.

I don't think anybody on this list runs an inverter that doesn't have suitable anti-islanding. The popular Infini is approved!

Even the older Victrons are perfectly fine, they just fall foul of the requirement that there must be two switches and one must be mechanical. The 2017 model will fix this :-)

To be honest, I don't even know what we're arguing about. Are we arguing? You're right for the most part. I'm just pointing out that the CoCT guys are also kinda right :-)

Edit: Also, connecting a non-approved inverter that does not properly island could provide something for another approved inverter to tie with! That is what I am harping on, that bringing in just one such non-approved inverter, combined with the right kind of circumstances, could cause even the approved once to do the wrong thing.

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17 minutes ago, plonkster said:

If you don't have such an inverter

If our inverters with the double protection doesn't make it to the list soon, I will be more than happy to add that nice anti islanding device Victron  recommended to use in conjunction with their older inverters to make the installation safe.. In the meantime I have added the contactor as an extra safety. Believe it or not, I do not want to be blamed for someone getting hurt because of my GTI. I am hoping that my Inverter will still make the list, It was only launched this year so i might still be lucky. If not it will cost me a couple of thousand more and I should be okay.

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4 minutes ago, Jaco de Jongh said:

doesn't make it to the list soon,

I wonder what it takes to get it tested and put on the list? Now that might be a good question to ask of someone at CoCT!

There is two anti-islanding devices that you can add on to a system, the Ziehl UFR-1001E, and the UfE ENS26. They aren't cheap. The Ziehl is on the CoCT list, so adding that should be enough. It's 450 Euro though!

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11 hours ago, DownTime said:

  The head of the Fire station needs to do a site visit once everything is done and then notes it down in their records.  Neither of the other two municipality's state anything regarding a fireman's switch.

I wonder how long this service will be free, til turns into another cash cow.

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On the topic. Interesting article of island power systems (this time for actual physical islands) :-)

http://www.powermag.com/marooned-how-island-power-systems-keep-the-lights-on/

Hawaii, apparently those guys have at least 120% and as much as 250% of minimum load worth of PV... that is when the sun is shining, they can power everything with it and have more than half the energy spare.

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On 2016/11/28 at 2:48 PM, Jaco de Jongh said:

In Capetown yes, connecting without an approval letter is illegal, in Phalaborwa their is nothing preventing me from doing so. Only once the bylaws state I need a approval letter, can my installation be seen as illegal.

I do not want to enter this open ended debate, but just need to caution you that there are indeed By-Laws in your little town of Phalaborwa deeming it illegal to connect your GTi to the grid connection without prior approval letter from your local municipality.

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13 minutes ago, Riaanh said:

to caution you that there are indeed By-Laws in your little town of Phalaborwa deeming it illegal

Thanks Riaan, Will visit them again and find out, Went to their offices on four occasions all ready, asked them for all the laws and bylaws for solar and grid tie. They Clearly stated that there are no laws in place at the current moment. They promised they will have a look into it as soon as they are finished with passing the law that states that a Generator can only be installed in conjunction with a changeover switch. I followed up telephonically after my last visit and every time I still get the same answer, "No laws yet, we are looking into it".

Maybe they have changed something, thanks for letting me know.  

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11 minutes ago, Riaanh said:

I do not want to enter this open ended debate, but just need to caution you that there are indeed By-Laws in your little town of Phalaborwa deeming it illegal to connect your GTi to the grid connection without prior approval letter from your local municipality.

They changed his meter after he told them, so I'm sure Jaco is good ;)

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36 minutes ago, Jaco de Jongh said:

O Ja and I forgot about this visit, the Export tripped my Prepaid, I went and told them about it, they asked what Grid Tie is and after I explained, they said "No problem, we will replace it" And they did. 

What meter did they replace your old one with?  Some Conlog pre-pay meters are very sensitive for any export and will trip and reset itself after a couple of minutes, other meters will "see" the export as power being used and then you use more units.  It can be quite a headache as some of the grid limiters that can be installed on the SMA, Socomec and Solar Edge Grid Tie Inverters  can take up to 3 seconds to react, which causes the meter to trip.

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