Questions to the City of Cape Town: SSEG installs / sign-off

[Rautenk]

Dear all,

I would like to start a monthly Questions to Cape Town campaign and use this forum to share the answers.

I have had very good and extremely detailed responses from CoCT to date and it might be best to help them out a bit by putting it all in a place where everyone can find it and give us a structured way to approach the guys. They are a bit overworked with all the applications and questions coming in.

 

So please fire away, where the CoCT has responded to previous questions to them (or where the answer is known between those here) it can easily be put here.

 

I hope I am not opening Pandora's box here...

[Guest]

Suggestion. Generally speaking there are two kinds of people on this forum:
1) The ones who can understand a electrical diagram and relate that to parts needed and where to install them.
2) Then there are those who need to be told what part/s to get and where to install them - people like me.

Like i.e. this "diagram" translated means you have to install a "Hagar 60amp double pole breaker" between your DB and your inverter.  

Would really help a lot for us non-technical people.

 

[Fuenkli]

20 hours ago, Rautenk said:

I would like to start a monthly Questions to Cape Town campaign and use this forum to share the answers.

excellent idea.

Herewith my first question:

1. I have read the entire thread about the 3.5kW inverter capacity limitation for hybrid GTI's. Now I am more confused than ever how to proceed with my application to the CoCT. Can you please get an answer what the correct approach for owners with existing systems with inverters exceeding the above limit is. I have a Goodwe GW5048D 4.6kW inverter with 4.4kW of PV and 20kWh battery capacity. The grid supply is single phase 60A with a prepaid meter. The system is on line since July 2018.

 

[flamegrilled]

1 hour ago, Fuenkli said:

with inverters exceeding the above limit is

I will have 4.4 kw on a 4.6 kw gti non hybrid on a 60 amp prepaid meter too.My hybrid is an Axpert with a bank only.AC charged.All Self consumption.

[Fuenkli]

2 hours ago, Fuenkli said:

The system is on line since July 2018.

correction. System is online since July 2017

[Jaws]

How does  City of Cape Town define :

1.Grid-tie

2.Grid connected

3.Hybrid

 

Edited January 28, 2019 by Jaws

[cpbotha]

On 2019/01/25 at 11:46 AM, Fuenkli said:

excellent idea.

Herewith my first question:

1. I have read the entire thread about the 3.5kW inverter capacity limitation for hybrid GTI's. Now I am more confused than ever how to proceed with my application to the CoCT. Can you please get an answer what the correct approach for owners with existing systems with inverters exceeding the above limit is. I have a Goodwe GW5048D 4.6kW inverter with 4.4kW of PV and 20kWh battery capacity. The grid supply is single phase 60A with a prepaid meter. The system is on line since July 2018.

 

Hi there @Fuenkli - I would like very much to keep up to date with your CoCT sign-off endeavours.

As you know, I would also like to get in the same GoodWe boat as you, but I'm currently flip-flopping between the 3.6kW EM (purely because of all the confusion around CoCT regulations) and the much more preferable 5kW EM or the 4.6kW ES. At this moment I'm almost ready to give up and just get the 3.6kW to play it safe.

[Fuenkli]

27 minutes ago, cpbotha said:

Hi there @Fuenkli - I would like very much to keep up to date with your CoCT sign-off endeavours.

I have submitted my application to connect a Goodwe GW5048D-ES inverter to the grid 4 weeks ago. I do not have a reply from the CoCT yet. I will update the forum on progress. Is there anybody in CT on the forum who has successfully gone through the process?

[Guest]

56 minutes ago, Fuenkli said:

Is there anybody in CT on the forum who has successfully gone through the process?

I did it about face. Was busy with the CoC with Engineering signoff only much later when I sent in my form as logic dictated they will respond saying no / yes or whatever.

So mine went in Oct 2018, was lost, sorted in Nov when I got my number.

Min 6 months they said.

Deadline has been extended so I recon once I send in the fully completed form (maybe next 2 weeks), just engineering report outstanding, that it will take them a year.

At least I would have papers to say it was installed properly for say like their is a claim.

Edited February 13, 2019 by Guest

[Elbow]

Hi Karel,

Having carefully read through the CoCT "Requirements for small-scale embedded generation" document and after a long time spent getting to know this field, here is what is not clear to me.  

1. What are the following, exactly, when are they required, and what do they do in the context of the document.  Example product names would help.  Don't inverters have this stuff built in already?
   • "Reverse power flow blocking relay"
   • "Reverse power flow blocking device" - is it the same thing?
   • "Reverse power flow blocking protection" - is it the same thing?
   • "Suitably interlocked change-over switch" (Appendix 4 really doesn't clarify what this does for me since it opens with a very wide-ranging list in (a))
2. If you pay for an AMI meter to be installed, does this meter itself provide the ant-islanding and other features that the CoCT wants to be present?  If so, it might be more cost-effective to go this way if you are going to need to spend nearly as much on some external automatic change-over switch and/or anti-islanding device.  Especially since grid-tie with sell back into the grid is a very simple way to install.
3. Where do we stand with inverter approvals on the 2010 and the 2017 standards.  Mine is approved on the 2010 standard.  So at the moment I can get "retrospective" approval for my system using this inverter but I can't present a new install using it since 2018-12-31 has come and gone.  So right now I'm motivated to rather install and then go to the CoCT for retrospective handling of my existing install.  This is confusing.  My inverter model is no longer sold (at least in its current branding) so I will not be able to get a test result for the 2017 standard.  Confusingly, my inverter is "on the list".
4. Diagrams are supposed to show the point of common coupling.  I don't know where the wires go when they leave my property - how do I know where this point of common coupling  is?

Another question - the "off-grid" says that it is an SSEG that is not and can never be connected to the utility grid - either directly or through my "internal wiring".  "Can never"?   Does that extend to plugging my inverter power input into an ordinary 15A socket using an ordinary plug?  I ask since typically SANS 10142 normally stops at the power sockets

I didn't look yet in detail at the application form but if I remember there are questions there which are above my understanding - I'll look at it and post my thoughts.

Steve

 

[___]

7 hours ago, Elbow said:

"Reverse power flow blocking relay"

Here is the thing about AC. Voltage and current changes direction 100 times a second. Current literally flows backwards and forwards, so the conventional DC "diode" idea of blocking simply does not apply. If the current waveform is in sync with the voltage waveform -- you may remember from high school that multiplying two negative numbers yield a positive one too -- then power flows in the one direction, and if they are out of phase (ie current is negative when voltage is positive), then power is going to other way. So electrical people talk about the "power vector", which is what you get when you multiply volts, amps, and the phase angle.

Now it gets really interesting, because for loads with a non-unity power factor, it pushes back a little bit into the grid on literally every cycle (ie there is a bit at the start/end of a cycle when power is going the wrong way). I sometimes picture it as a man drinking from a water bottle back-washing a little bit back into the bottle on each gulp, and then consuming it again on the next one... yeah a bit of an odd picture. My point: Well power flow is really more of an affair of averages... that on average more goes in the one direction than goes in the other.

Like playing Texas Holdem in a Casino. Doesn't matter how often you lose, what matters is that you win more often than you lose

So.... reverse flow blocking devices really doesn't do any blocking at all. They simply attempt to minimise slosh-back into the grid by adjusting power levels to keep them around zero.

Reverse flow avoidance should not be confused with anti-islanding. Reverse "blocking" is about not feeding power into the grid (on average) while the grid is alive, while anti-islanding is about not energising it at all when it is dead! Completely different things really.

[Elbow]

4 hours ago, plonkster said:

So.... reverse flow blocking devices really doesn't do any blocking at all. They simply attempt to minimise slosh-back into the grid by adjusting power levels to keep them around zero.

Reverse flow avoidance should not be confused with anti-islanding. Reverse "blocking" is about not feeding power into the grid (on average) while the grid is alive, while anti-islanding is about not energising it at all when it is dead! Completely different things really.

Hi @plonkster,

So your explanation is how I would have understood reverse power blocking.  Making sure the "smoothed average” energy flow at the measured point remains zero or inward.

but I don’t see how you do that with a "relay".  I suppose the term must be loose but I don’t think a doc like this should have loose terms.

Is reverse power blocking actually an inverter feature? Or are they expecting an external device?  How is an external device supposed to control the energy that a grid-tied inverter is pushing to the grid?  Maybe there is a control signal going back to the inverter?

My inverter is grid tied but programmed to off-grid mode.  So it puts out 0 power on the grid side.  Am I done?

Also, it supports an external current probe so it could zero at the main grid connection which for me meets the requirement for zero reverse current flow (well, on average). Is that satisfactory for the council?  In principle it is the same as having a fancy external "reverse current flow blocking device" except that a CT probe is simple and cheap.

Do you know what devices meet CoCT requirements?

[phil.g00]

An AC power directional decision can be made by referencing voltage and current simultaneously.

Current direction without a reference is a meaningless concept for AC. It appears that a current probe can be used as a stand-alone device on a particular circuit, but this isn't so, it's just that the inverter already has an internal voltage reference.

Directional flow is a function of the vector difference in of  the source voltage bus  and the load voltage bus across the impedance of the connection between them.

It is quite a head-wrecker as it possible to import and export Watts whilst importing and exporting Vars independently.

The vector sum of watts(P) and vars(Q) = VA(S)

An external relay doesn't regulate power flow it just will react to it, say open a contactor to the grid ( to prevent backfeed) or close a contactor on to a load (to increase self consumption).

This will be a fast stepped response.

An inverter is capable of adjusting quantities to regulate power flow, but it will only see the quantities (V & I) at its position to determine the power flow.

This will be a smooth response over time.

A paired smart meter is capable of telling the inverter these quantities at a remote position so that the inverter can respond to the power flow at a remote point in your network.

Just for completeness of the reply, an islanded hybrid inverter (off-grid) inverter may also have the capability of throttling the power of another downstream PV inverter through frequency shifting or in some cases a direct protocol. Many PV inverters can also achieve this independently using their own paired smart meter.

A lot depends on the particular inverter as to its capabilities.

 

[___]

1 hour ago, Elbow said:

but I don’t see how you do that with a "relay".

Me neither. Which is why I think the term might be composed from  incorrect conflation of the the two ideas (avoiding feed-in and anti-islanding). Anti-islanding is generally done with an actual relay (two actually)

2 hours ago, Elbow said:

Is reverse power blocking actually an inverter feature? Or are they expecting an external device?  How is an external device supposed to control the energy that a grid-tied inverter is pushing to the grid?  Maybe there is a control signal going back to the inverter?

Depends. For some it is built in, for some it is external. It does not matter, that's just a matter of packaging. In almost all cases it takes the form of some kind of current or power measurement on the input side that is read by the embedded computer of the device, that adjusts the amount of power until it's close to zero. Quite often it is an external device that forms a control signal back to the inverter, as you put it.

[Elbow]

3 hours ago, plonkster said:

Depends. For some it is built in, for some it is external. It does not matter, that's just a matter of packaging. In almost all cases it takes the form of some kind of current or power measurement on the input side that is read by the embedded computer of the device, that adjusts the amount of power until it's close to zero. Quite often it is an external device that forms a control signal back to the inverter, as you put it.

So - this is why this is confusing.  It's written in a sort of semi-abstracted style.  We are just practical people who want to know what is required and roughly why.

So my position is that my inverter has everything required.

Here it is on their list:

Valid until the end of this year.  So I shouldn't take too long to get going.  It doesn't have any weird notes in the list.

It meets the following standards:

For "grid-tied hybrid sseg" I must island - data sheet says that my inverter has anti-island protection integrated:

Then on the matter of blocking reverse power (if that's what I elect to do) - well the inverter has multiple ways to disable feed in to grid including using the off-grid modes.  PV power is used for charging and supplying load only, and never pushed out on the grid side.

So - is my reading correct?  Do I need to send in a design with no external devices and have them tell me they are not satisfied?

 

Edited February 19, 2019 by Elbow
typo

[___]

42 minutes ago, Elbow said:

So - is my reading correct?  Do I need to send in a design with no external devices and have them tell me they are not satisfied?

Yeah, that is pretty much what I intend doing, and what @The Terrible Triplett has already done. Apply, get the reference number... and then we will see when we get to sign-off. Between now and then lots can still happen. Then when they do tell us "this is not good enough", that doesn't mean you start from scratch... you still have your reference number, you fix and submit again. All else fails... you go (partially?) off-grid.

[Elbow]

13 minutes ago, plonkster said:

\you go (partially?) off-grid.

So my thinking was to register my system as an off-grid system (and use it that way - so I get some value), and then immediately put in the application for grid tied hybrid sseg and walk that journey until its approved.

[Guest]

29 minutes ago, plonkster said:

All else fails... you go (partially?) off-grid.

Ditto, off-grid with all bar the two kitchens. To do that, I simply remove the heavy circuits into their own DB, leaving the existing DB as is in place.

Seems like I have sat and pondered this move. 

All I need is a bit more battery capacity and 2 more panels (maybe)... like you say, we don't have to "start from scratch".

 

13 minutes ago, Elbow said:

So my thinking was to register my system as an off-grid system (and use it that way - so I get some value), and then immediately put in the application for grid tied hybrid sseg and walk that journey until its approved.

Have my approval to go-ahead, all I need is Rautenks report, and we have a plan.

So your inverter is on the list, go for grid tied first, see what comes out. It could take from end of May (3 months from now), add 6 months to that, so now we are 9 months later, give another 3-6 months to then affect any changes, so maybe a year from now in which time the regs could be more saner.

Going the other way just prolongs your stress.

And guys, what I see, chose the right inverter. If you change it one day, you need to do the papers again. 

Edited February 19, 2019 by Guest

[___]

Just now, The Terrible Triplett said:

more saner

LOL. I love the way African people (that includes us people of former European descent) use these redundancies... "You too can be more better!"

[Elbow]

1 hour ago, plonkster said:

 "You too can be more better!"

More better is obviously more better than betterer

 

[Elbow]

22 hours ago, Elbow said:

If you pay for an AMI meter to be installed, does this meter itself provide the ant-islanding and other features that the CoCT wants to be present?  If so, it might be more cost-effective to go this way if you are going to need to spend nearly as much on some external automatic change-over switch and/or anti-islanding device.  Especially since grid-tie with sell back into the grid is a very simple way to install.

Does anyone want to have a go at this question?

[___]

8 minutes ago, Elbow said:

Does anyone want to have a go at this question?

No. The meter doesn't do that. The only device that can adequately do anti-islanding is the inverter, because at least one active measure is required. So even if the meter could do such a thing (which it doesn't), it would only be able to implement passive measures (like the Ziehl does).

[Fuenkli]

Just for information. It has now been 4 weeks since I have submitted my application. Still no response from the CoCT .

[Guest]

3 hours ago, Fuenkli said:

It has now been 4 weeks since I have submitted my application. Still no response from the CoCT .

In contacting them direct, they said up to 6 months.

Mine was sent in Oct, lost and "found" again end of Nov (email issues) when I got a recipient confirmation number and middle Feb when I got the go ahead for the install.

[flamegrilled]

On 2019/02/19 at 3:04 PM, Elbow said:

AMI meter

@Elbowhave you done any Youtube research on the AMI meter? I did and did not like the meter after that and to make things worse you have to pay upfront and a monthly fee.