49 minutes ago, Hannes7212 said:

If our grid has to pick up a load of the UPS DB board that exceeds the ADMD of the design standards upon change over of the change over switch it can destabilize our LV network

What about inserting a fast acting 15A CB between the inverter and the grid? This was one of the proposals to the CoCT i considered to get my 4.6kW GTI application approved. I did however not proceed with this idea because the inverter manufacturer (Goodwe) has promised me a software solution to limit the power to 3.6kW.

removed duplicate post

Edited June 5, 20197 yr by Fuenkli

1 minute ago, Fuenkli said:

3.6kW

So, I have two questions.  Various folks are saying various things on various numbers.

So far as I understand it, the limit for a GTI is 3.5 not 3.6.  So if I want an inverter given the rules I would need to go for one of these instead of one of these?

The rules from CoCT appear pretty clear on this.

So what gives on the 3.5/3.6 numbers going on here on the forum?

Further, the main breaker is generally rated at 63A not 60A (it actually says so on my breaker). 

Would this make any material difference to the above 3.5/3.6 number?

Don't flame me, just asking because I am a bit confused on the numbers.

13 minutes ago, IdlePhaedrus said:

So what gives on the 3.5/3.6 numbers going on here on the forum?

I am also not sure. According to NRS 097-2-3:2014 it is 3.68kW

49 minutes ago, PeterP said:

1. The 3.5kVA limit is there to ensure all grid-tied SSEG customers remain net-consumers (import more than they export) + to limit excessive feed-back. The UPS/Off-grid generator cannot export hence this does not apply.   

I was told it's about the pick-up, the amount of load the grid has to take on due to your generator tripping.

50 minutes ago, PeterP said:

I don't see what patterns they create that are any different to flicking a switch on any appliance

I agree with that, but for the most part (except right after a power failure, when all the fridges, freezers and geysers want to run), you don't turn everything in your house on simultaneously. I'm arguing that a large off-grid system (for example, a 15kW one that can carry 100% of the rated power) would do exactly that.

But for the most part I agree with you. The pick-up pattern is completely different.

5 hours ago, Hannes7212 said:

For stand alone off grid system that is not connected in anyway to the internal wiring of the domestic premises or the grid the 25% does not apply.

Good, so it still is as I understood it.

But a new caveat: If you have a changeover switch with a off-grid setup, you are limited as per NRS regulations. 

3 hours ago, Fuenkli said:

 

This is the one on CoCT's paperwork.

8 hours ago, PeterP said:

2. I don't see what patterns they create that are any different to flicking a switch on any appliance - home-automation could create the same patterns.

Been thinking on this.

If I was off-grid with Eskom as backup, inverter powering 4kw from the panels / batts (pool pump, geyser/s), I would be switching that lumped load off the batts if they get to X SOC.

So no, that is not an issue.

However, the issue starts when that is multiplied with 1000 or 10 000 solar installs. That changes the picture rather massively.

I am led to believe that CoCT has called on the expertise of European country/ies that has gone though this before, having learnt a lot of what not to do. 

So these rules are not about the individuals and their constitutional right. These rules are to protect our regional / national electrical grid and that also falls under the constitution, to be protected. And registering the system as off-grid, well that is simple: To stop wasting ratepayers money to employ people to check if a site is grid tied or not. 

I don't think CoCT is being unreasonable. Yes they are new to this, yes they are strict and non-negotiable, but they do not have their knives in for us or are trying to throw us under the bus. That is just plain conspiracy theories. 🙂 

As I see it, If anyone disagrees with the rules, your right to do that, then disconnect Eskom, register as a off grid site, and do as you please. That is your right.

However, anyone connecting anything to a DB that is connect to the grid, now that affects OUR rights. 🤔

Quote

However, the issue starts when that is multiplied with 1000 or 10 000 solar installs. That changes the picture rather massively.

Wouldn't be anywhere near as bad as the massive load switching that occurs at the end of a load shedding interval.
After 4h of no power to the entire neighborhood with geysers cooled down and fridges and freezers warmed up and then bang on the entire local network at close to maximum load at each individual household.

Quote

So these rules are not about the individuals and their constitutional right. These rules are to protect our regional / national electrical grid and that also falls under the

Note that my post regarding a constitutional right to privacy specifically referred to systems that in no way had any connection to a municipal grid and thus in no way infringe on anyone else's rights.

17 hours ago, Fuenkli said:

I am also not sure. According to NRS 097-2-3:2014 it is 3.68kW

So those PF members with off-grid installs will be looking for another source of power other than the "Utility" and assuming the setting would "SBU" with U being on prem AC source. yes/no?

17 hours ago, Fuenkli said:

I am also not sure. According to NRS 097-2-3:2014 it is 3.68kW

Thanks, I will look that up later today and give it a read.

9 hours ago, Power Me said:

Wouldn't be anywhere near as bad as the massive load switching that occurs at the end of a load shedding interval.

True... the difference is you KNOW this one is coming and you can manage it. It's a bit different when you're at the mercy of the weather (again, don't get me wrong, I don't necessarily agree with their interpretation, just trying to be fair by acknowledging it's not exactly neutral).

So, I have read through NRS-097-2-3-final-2014.

It says the following with regards to the limits that @Fuenkli posted:

Quote

 

NOTE The values have been adjusted to align with VDE-AR-N 4105 and hence vary slightly from 25 % of the NMD. For circuit-breaker sizes not included  in  table  1,  the  maximum  individual generation  limit is 25 % of the customer notified maximum demand, i.e. 25 % of the circuit-breaker size. The individual limit is only dependent on the service circuit-breaker rating, and not on the feeder After Diversity Maximum Demand (ADMD). Future refinements of these criteria will assess the incorporation of ADMD into the decision framework.

So, the NMD for a 60 amp breaker is 13.8 KVa, thus 25% is 3.45 KVa (3.5 rounded up).

So, I believe that CoCT has gone with the strict 25% of NMD rather than the adjusted values given VDE-AR-N 4105.  It is a partial interpretation and thus to my mind irrational in terms of the law and disqualifies CoCT from saying 'we are just applying the NERSA rules'.

This explains the discrepancy, but it doesn't explain why they have chosen to do this given NRS and VDE-AR-N 4105 and inverter sizes in this range.  It isn't just a 0.1 KVa limit, it is in effect is a 0.6 KVa limit.

This doesn't really affect me as I only have 3kw of panels, but I do have space for a couple more, so I would likely have gone for a 3.6 inverter so I could safely add a couple of additional panels down the line if I wanted to.  But I am sure there are plenty of folks which might have existing 3.6 installations.

Anyway, while I was doing my Google Fu I found this document which others here might find interesting as it covers training for all the NRS and SANS specifications for SSEG: https://solar-support.org/files/295/dump

 

On 2019/06/05 at 3:50 PM, Fuenkli said:

What about inserting a fast acting 15A CB between the inverter and the grid? This was one of the proposals to the CoCT i considered to get my 4.6kW GTI application approved. I did however not proceed with this idea because the inverter manufacturer (Goodwe) has promised me a software solution to limit the power to 3.6kW.

I think that is a very elegant proposal.

In my experience so far - COCT is not going to look at anything that is not straight forward and ticks their simplified boxes. Don't bother with clever ideas. 

I had a bit of a mission just getting them to correct the forms they sent me including the permission to install letter so it actually matched what I applied for. It's not smooth sailing so keep it simple. Really simple.

 

1 hour ago, The Bulldog said:

In my experience so far - COCT is not going to look at anything that is not straight forward and ticks their simplified boxes. Don't bother with clever ideas. 

I have a feeling that once the dust settles down, once NERSA gets their act together and things become a bit more national, and once the industry itself becomes a bit more well understood (what is available, who makes what), at that point you might be able to sneak something a bit more technical in, but right now they are only doing the easy stuff.

On 2019/05/29 at 9:58 PM, Rautenk said:

Some interesting facts:

1. No budging on the >3.5kW on 60A breaker

2. No installing 80A for SSEGs only (network issues)

3. CoCT doesn't give a damn about Axperts, you may install them at leisure. However you need to get an electrician to sign-off on the "off grid" status. 

(You DECLARE off-grid, not register off-grid). They just wanted to clear that up..

4. Users with greater than 100A, you are treated differently (sorry)

@Rautenk can you shed some more light on #2?

My application for the 80A was approved, I've paid the people, and work is about to be scheduled.

I didn't mention anything about SSEG on my application, although it is in fact the plan to integrate the GoodWe 4.6kVA ES. However, there are 6 people living on my premises, so maybe that helped the request?

18 hours ago, cpbotha said:

My application for the 80A was approved, ...

I didn't mention anything about SSEG on my application, ...

And that is why you got it done I would think. 

Now to see how many people can do it like this before "they" catch on. 😉 

20 hours ago, cpbotha said:

My application for the 80A was approved

I am not surprised as NRS 097-2-3:2014 Section 4.2.5 states the following:

"If the maximum individual generation limit is exceeded, the customer could potentially be connected through a dedicated LV feeder, such that the generator is supplied through a dedicated LV Feeder(and the dedicated feeder limits apply) Alternatively the customer can apply for an increased NMD e.g. if a customer with a single phase 60 A supply wants to install a generator greater than 3.68 kVA then the customer could apply for an upgraded supply to three-phase 60A whereby the maximum generator limit increases to 13.8 kVA"

On 2019/05/30 at 11:15 AM, The Terrible Triplett said:

I want to understand the big picture

Technical Reason for 25 % of NMD Limit: 

NRS 097-2-3:2014 Table 4 and Table 5: show that the technical reason for the limits imposed on generation has to do with grid voltage regulation and maintaining the NRS 048-2 limits especially concerning overvoltages.

Calculations show that when minimum loading and maximum generation coincide then the maximum LV voltage could be as high as 111.1%:  (Which is in fact 1.1% higher than allowed)

A) Maximum MV voltage for normal operation.

 Minimum Transformer loading of 0%

C) Maximum generation level of 75 % of the transformer rating.

D) 1% maximum allowed LV feeder voltage rise.

   

Edited June 13, 20197 yr by Carl

4 hours ago, Carl said:

Calculations show that when minimum loading and maximum generation coincide then the maximum LV voltage could be as high as 111.1%:  (Which is in fact 1.1% higher than allowed)

Thanks Carl but I have no idea what it means in laymen terms. 🙂 

4 hours ago, Carl said:

Calculations show that when minimum loading and maximum generation coincide then the maximum LV voltage could be as high as 111.1%:  (Which is in fact 1.1% higher than allowed)

This is an excellent post. To help @The Terrible Triplett, and if I understand this correctly, whenever you stick energy into a system it tends to push the voltage up slightly, and as that energy dissipates the voltage drops down again. It's exactly like the water level in a water tank. When the load is very low (little to no consumption by the houses in the area), and the sun is shining brightly, then the voltage could rise up to 11% even at the existing 25% allowance, and that is already 1% too much.

29 minutes ago, plonkster said:

When the load is very low (little to no consumption by the houses in the area), and the sun is shining brightly, then the voltage could rise up to 11% even at the existing 25% allowance, and that is already 1% too much.

I understand the logic assuming you are feeding into the grid. But this is not the case in Cape Town. Most of us have chosen the SSEG option with zero feed in and keeping the existing one way pre paid meters. In addition I thought that the inverters have to stay in very strict voltage and frequency limits. 

15 minutes ago, Fuenkli said:

I understand the logic assuming you are feeding into the grid. But this is not the case in Cape Town. Most of us have chosen the SSEG option with zero feed in and keeping the existing one way pre paid meters. In addition I thought that the inverters have to stay in very strict voltage and frequency limits. 

Well, I've heard two stories now and chances are both are true. If you feed in too much, you risk raising the voltage above the 10% allowed, but you also increase the amount the grid has to pick up if your generator trips. I suspect that they might be able to handle a bit more on the pickup side (as some have pointed out, picking up 5KW is really not a biggie), so this is probably the result of a comprehensive assessment that looked at both sides. Or such is my guess at least.

Re strict voltage limits, I see that it is 195V on the low end and 253V on the upper end (for 40 seconds, 265V for 2 seconds), in other words it seems the inverters use the same 10% margin. So yeah, they will prevent such overvoltage, but imagine you're the guy with the 3KVA link and you can't push into the grid because your neighbours with their 10KVA setups are pushing the voltage up... 🙂

So CoCT made an interesting update to their website:  http://www.capetown.gov.za/City-Connect/Apply/Municipal-services/Electricity/apply-for-authorisation-to-install-a-small-scale-embedded-generation-system

"If you do not intend to feed in to the grid, .... A prepayment meter is required and will be installed by us at our cost."

This is different to the quote they sent me a few months ago where I had to pay R2200 for the new meter.

 

3 hours ago, Niel said:

... at our cost."

I got a free PAYG meter last year when they ran a "special" in our area for one month. If you said yes in that month, you got one free.

Impression I got was that they want to get rid of all older meters ASAP as it costs them time and money (read our rates and taxes) to read the old tech manually.

So extending it for "free" again for solar installs, CoCT rocks. 😜

Now just the 5kva GoodWE's and the 3.5kw limit ... 😉