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CoCT and CoT SSEG Maximum PV Inverter Size (Fronius) in a Victron Energy Storage System


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Hi, for those who have experience of the CoCT and the draft CoT regulations, I would like to ask the following for a 60Amp Single Phase Residential Supply with a conventional meter:

If I have a Fronius 5.0-1 (5kW) PV Inverter AC Coupled on AC Out and a 250/85 PV Charger (4.08kW) DC Coupled with 9kWp of actual panels (rating) which can produce a maximum of 8kWp of power due to west facing azimuth of some of the panels and I use the feed-in register of the SCADA system (Cerbo) to limit feed-in (set it to 34 =3.4 kW), I have 22.2 kWh of lithium storage, does this qualify for SSEG ? 

My actual feed-in will be negligible, I worked out that the maximum feed-in using SPU-1 tariff has a return on investment of 14 years which is longer than the RoI of the rest of the system so, it is not worth doing under any circumstances, hence the best approach here would be to give my excess power away to the city for free, the CoCT document states that you have to use the SPU-1 tariff but contradicts itself later when it says that you can SSEG connect and give the power away for free using a prepaid meter and your existing tariff, Which is it ?

Next lets look at going off grid / Passive UPS, neither of the stated cases apply to what I want to do which is use it as a Passive UPS at night (Using Grid Passthru on the input AC input through to the Output AC) and "OFF-Grid" during the day, I am not generating or self consuming at night, I can even interlock it to the remote power function on of the Multiplus II 5000 to put it into charging only mode to prevent it inverting, this also prevents the Fronius from inverting if the ATS jams during load shedding (Annex 4 item b), during the day I can completely disconnect from the Grid and reconnect switch back to Passive UPS mode with the ATS if the battery becomes too low on a dark day (using the relays and battery level monitor), here I can set Fronius zero feed in and set the Multiples to not feed-in (invert) Solarcharger power when the battery is full.  During the day, the system is effectively "Off-Grid" and during the night it is in "Passive UPS Mode", is this allowed and does it pass the Municipality "Smell test" because I am doing both "Off-Grid" and "Passive UPS" at different times of the day and not one or the other ?

Technically I can generate 5kW from the battery using the MultiPlus II and 5 kW from the Fronius at the same time, also the spec of the Fronius is above the 3.5 kWp, but it is not being used on AC Input, (traditional Grid Tie), rather it is on AC Output and is Software controlled, I want to use a Fronius 5.0-1 (5kW) due to high domestic power consumption

Technically I am using the ATS to switch the AC Input to the Multiplus from Grid to nothing (or diesel generator) and not the loads, is this allowed because that would not switch the loads between SSEG output and Grid?

I could switch both the inputs and the outputs using the 4 pole ATS, but then I loose the remote interlock, need to think about how to use only 1 common pole or will need a 5 pole ATS

SO in TSHWANE,

I understand that the regulations are informal in Tshwane and that any SSEG application results in a forced meter change when the final regulations are not promulgated and may still change, this tells me that making an application is a bad idea as it could cause a double spend on meters and clearance certificates and consultants, and that no one gets the SSEG tariff anyway which I didn't even see in the 2021 tariff table (it was R0.1 last year)

 

Thats quite a lot, have I got things about right ?

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I've been told that the limit is not about how much you feed in, but how much the grid has to "pick up" if your embedded generator trips. So if you have a 5kW generator and you also have 5kW of loads on your property (so an ideal situation with 100% self-consumption and nothing is fed into the grid), and your PV-inverter switches off for whatever reason (trips), then the grid has to pick up 5kW, which is more than 25% of your connection size, and something they don't want.

In practice however, we've seen them sign off 5kW systems with large battery banks (hybrids, so the ability to carry loads from the batteries adds to the picku-up) as long as the PV component is below 3.5kW. At the time, I said to the poster: Let sleeping dogs lie.

Soooo.... my gut feeling is they won't allow this. Logically they shouldn't, if it really is about the pick-up.

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33 minutes ago, plonkster said:

I've been told that the limit is not about how much you feed in, but how much the grid has to "pick up" if your embedded generator trips. So if you have a 5kW generator and you also have 5kW of loads on your property (so an ideal situation with 100% self-consumption and nothing is fed into the grid), and your PV-inverter switches off for whatever reason (trips), then the grid has to pick up 5kW, which is more than 25% of your connection size, and something they don't want.

This is nonsense! If it were possible that all systems were somehow synchronised so that if one were to trip it would cause the others to trip then this argument might be plausible. Of course this isn't the case so a small pickup in grid load due to a inverter tripping is insignificant.

A plausible scenario however was in the positioning of the solar PV fnarms in the Northern Cape. The concern was that if these facilities were too concentrated then a cloud or local storm could abruptly reduce the feed to the grid by a significant amount. The solution was to disperse them widely so they aren't all affected by the same weather conditions.

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48 minutes ago, Richard Mackay said:

If it were possible that all systems were somehow synchronised

They are. NRS097 describes the exact operating conditions outside of which they must disconnect. Any even that trips one of them could trip all of them simultaneously.

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1 hour ago, Stanley said:

I think this latest document from CoCT explains the Inverter size limits much more clearly than previous versions.

Indeed, that is much clearer. It seems there is indeed an inverter limit AND a feed-in limit. 3.5kW feed-in limit, and 13kW inverter capacity.

18 hours ago, CCC Telecom said:

I use the feed-in register of the SCADA system (Cerbo) to limit feed-in

Are you talking about the new feature in Venus 2.60 where you can limit the amount the whole system feeds in? That was actually written for the German market (they have a 70% rule, you may oversize the array, but must limit your grid feed-in to 70% of the total), but can easily be used for the same thing in Cape Town. The trouble with this whole thing (at the moment) is that the speed at which the system pulls back is nowhere near what the rules asks for. The rules wants you to pull back 90% of the way within 2 seconds. But it is a software limit and it ticks the boxes, so.. maybe? 🙂

53 minutes ago, calypso said:

Its still a complete nonsense rule

I disagree. I read somewhere (I cannot remember where) how they determined this figure, and 25% is actually leaning on the generous side given the shape of our grid infrastructure. In places like Germany there are already protocols and standards for instructing grid-coupled PV-inverters to change their power factor. The grid can use the connected embedded generators to correct power factor... this is literally the level of control that will come, and we are a long long way off.

The German grid code also has a ramp rate (at which power is increased/decreased when it feeds into the grid), and that ramp is in both directions (in and out). We have none of that in SA. Until we do, we'll have to live with certain constraints.

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4 hours ago, Tariq said:

just to clarify, this has nothing to do with pv array size or am i wrong

Well, as I understand it, you can have as many panels as you like as long as your FEEDBACK to the grid is <= 3.5kW as determined by either hardware (inverter, PV panels) or software, which I think most inverters can do, limit feedback by software...

I do believe there were issues in CT initially where it became an issue with the number of panels one had if their capacity was > 3.5kW

Capture.PNG

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9 hours ago, Stanley said:

I think this latest document from CoCT explains the Inverter size limits much more clearly than previous versions

This is a much more reasonable approach. I am glad the CoCT has changed the rules. Based on the old rules i was forced to limit the maximum output (no feed in system) to 3.5kW. Do you know what the process is if i want to make use of the new rules and increase the PV capacity? I hope i do not have to go through the whole registration process again 🙁.    

Edited by Fuenkli
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On 2020/09/13 at 8:50 PM, plonkster said:

I've been told that the limit is not about how much you feed in, but how much the grid has to "pick up" if your embedded generator trips. So if you have a 5kW generator and you also have 5kW of loads on your property (so an ideal situation with 100% self-consumption and nothing is fed into the grid), and your PV-inverter switches off for whatever reason (trips), then the grid has to pick up 5kW, which is more than 25% of your connection size, and something they don't want.

In practice however, we've seen them sign off 5kW systems with large battery banks (hybrids, so the ability to carry loads from the batteries adds to the picku-up) as long as the PV component is below 3.5kW. At the time, I said to the poster: Let sleeping dogs lie.

Soooo.... my gut feeling is they won't allow this. Logically they shouldn't, if it really is about the pick-up.

The 25% limit is about how much the grid has to pick up when it reconnects after a grid-outage. The grid is designed to handle a % of possible loads off your standard supply - now add feed-in, and if left unregulated, you could have feed-in off over 100% plus your loads exceeding capacity of grid very quickly when grid is restored and everyone's load and feed-back resumes simultaneously.

If your embedded generator trips it not really a problem (no worse than switching on 2 geysers at the same time) as it's inconceivable that all other embedded generators (geysers on) trip at the same time - when a grid is restored after an outage, it all happens at the same time.

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6 minutes ago, PeterP said:

The 25% limit is about how much the grid has to pick up when it reconnects after a grid-outage

Again, a very reasonable rule to restrict maximum battery charge current to 25% of grid connection. I am sure most users support this. It will however be veeeery difficult to enforce. 

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On 2020/09/13 at 2:13 PM, CCC Telecom said:

I can even interlock it to the remote power function on of the Multiplus II 5000 to put it into charging only mode to prevent it inverting, this also prevents the Fronius from inverting if the ATS jams during load shedding (Annex 4 item b)

Please accept my apologies for making the above statement, it is not possible to interlock the MultiPlus II (any hardware version) because Victron changed the way the remote on/off switch works from the original MultiGrid/MultiPlus system, it now is a pure 2 contact on/off switch and does not have the 3rd Charger Only Mode pin, not all of the documents on-line reflect this change and maybe this is where the CoCT got their original clause (b) in Appendix 4 from.

The MultiPlus II can be put into charger only mode, but this is with the on/off switch at startup, so a hardware interlock in case contacts jam is much more difficult than I previously thought, hence my thinking is that if you have 2 transfer switches (one internal to the MultiPlus II and one an external ATS) then maybe clause (b) goes away? 

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On 2020/09/13 at 8:50 PM, ___ said:

I've been told that the limit is not about how much you feed in, but how much the grid has to "pick up" if your embedded generator trips. So if you have a 5kW generator and you also have 5kW of loads on your property (so an ideal situation with 100% self-consumption and nothing is fed into the grid), and your PV-inverter switches off for whatever reason (trips), then the grid has to pick up 5kW, which is more than 25% of your connection size, and something they don't want.

In practice however, we've seen them sign off 5kW systems with large battery banks (hybrids, so the ability to carry loads from the batteries adds to the picku-up) as long as the PV component is below 3.5kW. At the time, I said to the poster: Let sleeping dogs lie.

Soooo.... my gut feeling is they won't allow this. Logically they shouldn't, if it really is about the pick-up.

OK, so lets be a bit more specific

5kW rated PV Inverter (AC Output) - Fully panelled  

5kW rated Inverter Charger (to convert between AC and DC) rated at 70Amps DC Charging

4 kW rated PV Charger (DC output) - Fully Panelled 

To qualify for Grid Tied SSEG, this system would have to be software limited to 15Amps AC Charging = around 60 Amps DC (after losses) Charging and 3.5kW Feed-In and have a maximum inverter capacity of 13.8kW (in this case it is 10kW if you add the two AC sources), all of this can be done fairly easily BUT maybe the feed-in requires a technical knowledge of using Modbus TCP to set the register that limits feed-in on the venus or cerbo, I would have to check the latest menu software for the Venus/Cerbo to see how easy that will be, otherwise their are two other options get a 3.5kW PV Inverter instead and prevent PV Charger feed in (that is a menu option) or go for a non-grid Tied solution as follows:............

=Type 1: Passive standby UPS utilised as off-grid hybrid SSEG:

I still am not sure what one of these actually is and what the rules are around connecting it, I am assuming that there are a ton of rules about this not in the document, not sure what the interlock rules are here around the connections allowed for the transfer switch, because the document does not explain them.

IS it

1. Input to hybrid SSEG = Grid AND Output from hybrid SSEG = load (Condition = No Inverting takes place, locked by software, system is in Passthru mode)

   --- Or is GRID PASSTHRU just not allowed at all with a type 1 system (this is how every load shedding system is installed today which means they are all non compliant)

OR IS it

State A = OFF-GRID where 1. Input to Hybrid SSEG = Alternate Power source (Generator) or Nothing AND 2. Output from hybrid SSEG = load (GRID not involved at all)

State B = Passive Standby UPS where 2. Input to Hybrid SSEG = GRID AND 2. Output from hybrid SSEG = Disconnected AND 3. GRID = Input to Load (no passthru allowed)

The Make-Break-Make switch either manually or automatically switches between state A and State B above where state B has the hybrid SSEG as just another load able to use charging, or is using the GRID as a hybrid SSEG battery charger also not allowed?

 

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On 2020/09/14 at 7:30 AM, Stanley said:

I think this latest document from CoCT explains the Inverter size limits much more clearly than previous versions.

SSEG residential generation size limitations (2020-08-14) (003) (4).pdf 649.19 kB · 45 downloads

The item I am still unclear on is Category B = Grid Tied Hybrid SSEG which is a new category, I was going fine until I got to item 5 which says "If essential loads are interconnected with the grid, the Compulsory Isolation Change Over Switch ...", do you have any idea what they are getting at, it is grid tied, so of course the essential loads are interconnected with the grid, so in effect they are saying there is "a compulsory isolation change over switch required" without a hint of how they expect it to operate

So I guess they saying the following:

 A changeover switch is required to disconnect the SSEG Outputs from the load DB board and connect the main DB Board directly to the CoCT grid without using SSEG passthru, the changeover switch must simultaneously disconnect the CoCT grid from the SSEG AC Input thereby bypassing and isolating the SSEG from the CoCT grid and the DB Board

 

 

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6 hours ago, CCC Telecom said:

The item I am still unclear on is Category B = Grid Tied Hybrid SSEG which is a new category, I was going fine until I got to item 5 which says "If essential loads are interconnected with the grid, the Compulsory Isolation Change Over Switch ...", do you have any idea what they are getting at, it is grid tied, so of course the essential loads are interconnected with the grid, so in effect they are saying there is "a compulsory isolation change over switch required" without a hint of how they expect it to operate

So I guess they saying the following:

 A changeover switch is required to disconnect the SSEG Outputs from the load DB board and connect the main DB Board directly to the CoCT grid without using SSEG passthru, the changeover switch must simultaneously disconnect the CoCT grid from the SSEG AC Input thereby bypassing and isolating the SSEG from the CoCT grid and the DB Board

 

 

This is grid-tied hybrid, which is not quite the same as regular grid-tied PV inverters. A hybrid inverter typically takes PV and a Battery and can therefore supply the essential loads when the grid has failed. So in the case of a grid-tied hybrid inverter (hybrid inverter that runs in parallel with the grid) the internal changeover switch that disconnects from the grid when the inverter runs off-grid must comply with SANS 60947-6-1

(You will notice that Standby SSEG has the same requirement, so basically any time essential loads can be supplied by the grid and the inverter, there must be a changeover switch that is compliant with SANS 60947-6-1)

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7 hours ago, Stanley said:

This is grid-tied hybrid, which is not quite the same as regular grid-tied PV inverters. A hybrid inverter typically takes PV and a Battery and can therefore supply the essential loads when the grid has failed. So in the case of a grid-tied hybrid inverter (hybrid inverter that runs in parallel with the grid) the internal changeover switch that disconnects from the grid when the inverter runs off-grid must comply with SANS 60947-6-1

(You will notice that Standby SSEG has the same requirement, so basically any time essential loads can be supplied by the grid and the inverter, there must be a changeover switch that is compliant with SANS 60947-6-1)

Most of their SSEG policy seems aimed at maintaining or improving revenue at the expense of everyone else, hence I have taken the approach that current and future installations will have a standard hardware install with various electrical interlocks that can do both and that the choice of

Category B = grid tied Hybrid SSEG either with "uncompensated" feed-in or with the "customer makes a loss" "pay for the privilege" SSEG tariff 

Category C = Type1: Passive standby UPS utilised as Off-Grid Hybrid SSEG where I just throw the switch and go OFF-Grid during the entire solar day

Becomes a software configuration issue and not a wiring and installation issue, if the Municipality makes it expensive and painful people will remain off grid

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On 2020/09/23 at 2:39 PM, CCC Telecom said:

Most of their SSEG policy seems aimed at maintaining or improving revenue at the expense of everyone else, hence I have taken the approach that current and future installations will have a standard hardware install with various electrical interlocks that can do both and that the choice of

Category B = grid tied Hybrid SSEG either with "uncompensated" feed-in or with the "customer makes a loss" "pay for the privilege" SSEG tariff 

Category C = Type1: Passive standby UPS utilised as Off-Grid Hybrid SSEG where I just throw the switch and go OFF-Grid during the entire solar day

Becomes a software configuration issue and not a wiring and installation issue, if the Municipality makes it expensive and painful people will remain off grid

I agree, all installations should pretty much look the same whether you are using category B or C. If you have a look at this example circuit diagram that MLT Inverters supplies for a typical Oasis installation, the same external hardware such as the changeover switch (called a bypass switch in the drawing), circuit breaker, fuse etc. are all pretty standard for any type of installation. The added benefit of the external changeover switch is that it can appear (to most electricians and even the CoCT SSEG department) to fulfill the requirements of the changeover switch mentioned in the SSEG document. Since according to the drawing the load is supplied either by the Inverter or the Grid depending on  the position of the switch.

https://www.mltinverters.com/documents/Oasis-SSEG-Template-v1.1.pdf

For interest sake, even though the Oasis is a passive standby UPS, it has a built-in feature to allow you to make use of PV similar to you throwing the switch to go off grid during the day. It has a 'Battery Cycling' function, which allows you to set a time that it must go off grid and another time that it must go back on grid. It will then automatically disconnect from the grid at the battery cycling start time and reconnect at the end time. If you set the start and end times the same then it will stay off grid permanently. The nice part of letting the inverter do this rather than manually throwing the switch, is that it will reconnect to the grid if the battery gets low (you can choose at what voltage or SOC this happens in the battery settings. SOC for Li batteries with CAN, or voltage for all other types)

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