Hi,

With the new Smart meters rolled out by City of Tshwane, the inverters disconnect from the meter, or trip the meter, even when “feed in to the grid” is disabled.

 

What causes this, and what would the solution be?

3 hours ago, Frodo said:

What causes this, and what would the solution be?

Imagine trying to follow a drunk man, walking directly behind him as he walks down the street. Your task is to follow him exactly, if he swerves to the left, you could to follow suit, if he stumbles to the right, again you got to do the same thing. You're not going to be very good at it, because you're always reacting to his unpredictable movements.

The same thing happens with inverters that try to balance power to zero. They have to follow your loads exactly, feed in the exact same amount as the loads are using to cancel them out. The loads in a modern day home are not static. They are always fluctuating.

Whenever the inverter overshoots a bit, power flows into the grid. Whenever it undershoots, power is taken from the grid. The amount of power that flows into the grid multiplied by the amount of time becomes an energy value, and if this energy value is too high, the prepaid meter trips.

The probability of the meter tripping is therefore a function of the amount of accidental overshoot multiplied by the time period. All meters give you a little bit of grace, but lately it seems meter makers are pushing that number to be very low. To give you an example, a Conlog BEC23 meter might allow 40W for 15 seconds, which means 600W for one second, 300W for 2 seconds, 150W for 4 seconds, and so forth. A slow-responding inverter will easily avoid tripping on a small load, but will have trouble the moment you go to a higher load.

How do you avoid it? Well there's really only a few options.

1. Respond faster. Some inverters are better than others. Fronius, for example, has very fast tracking. I cannot say if it is fast enough for these meters, but I know it is quite good.

2. Run completely disconnected from the grid. If you're not connected to the grid, you cannot accidentally feed in. Not useful for purely grid-tied inverters.

3. Run with a high grid setpoint. Let me explain. Many inverters have a "setpoint", so instead of aiming for zero, you can tell them what power level to aim for. You might set this to 300W for example, then it will always use 300W from the grid and the rest from solar. The downside is you cannot lower your bill below this point. The upside is that there is an extra buffer of positive energy that has to be surpassed before the meter trips, which may give you a couple extra seconds and prevent tripping.

4. Beg your supplier to turn this feature off.

5. Register as a small scale embedded generator (in cape town there is a special tariff for such people) and pay for the bi-directional smart meter that comes with this.

Edit: 6. Divert the energy. There are devices that measure outgoing energy and when it detects such energy, it can turn on a load. It is mostly used with grid-tied inverters to dump excess energy into a hot water cylinder. Generally such diverter devices can react much faster than the inverter. With such a device you can divert all those little overshoots into hot water.

Edited May 28, 20197 yr by plonkster

In fact... I am now wondering how difficult it would be to close the relay in a Venus-GX/CCGX for a few seconds every time power goes negative. There's still going to be a delay, because in the kind of systems I work with we use Carlo Gavazzi energy meters and those can lag as much as 800mS, and then there's a bit more of a propagation delay, but in theory, if you react within 2 seconds with enough of a load, it just might work...

3 hours ago, Frodo said:

What causes this, and what would the solution be?

@plonkster has addressed the reason why this happens.  This has already been discussed with regards the Conlog meters in various threads.

27 minutes ago, plonkster said:

4. Beg your supplier to turn this feature off.

In this thread, @Charl_CCU said:

Quote

Thanks. Yeah I phoned Conlog and they determined it was indeed the feedback protection. They are going to send me the generated token to disable it once the engineers get back to them.

It would be interesting to know if you or Charl_CCU manage to get that token.

Bad news guys: I'm sorry to report this Conlog has said that Tshwane would rather you disconnect your system than try figure out a solution (an easy token).

 

Thanks for nothing DA. Why do they have this stance whereas in CoCT they are embracing it and even offering feedback at reasonable rates. I wonder if they really are experiencing technical challenges or if that is another cover-up story.

 

I'm not sure what my installer did but they got my inverter (SolarEdge) to stop tripping the meter. I'm not sure exactly which settings they changed but I've notice that no matter the PV output, at least 200W will always come from the grid. Has been working perfectly for a few days now. Perhaps try doing this with your inverter?

Letter.pdf

Edited May 28, 20197 yr by Charl_CCU

14 minutes ago, Charl_CCU said:

at least 200W will always come from the grid

That's the usual way to do it. Again, since it looks at the energy within a small time window (15 seconds on at least some conlog meters), if you run at 200W just prior to a large appliance turning off, you have 200*15 = 3000 joules in "savings", as opposed to the normal 600 joules if you were running at zero. That literally gives you 5 times more time to work with. But it means 4kwh from the grid per day. Which is fine if you're not covering your full load from PV... but many of us are.

11 minutes ago, plonkster said:

That's the usual way to do it. Again, since it looks at the energy within a small time window (15 seconds on at least some conlog meters), if you run at 200W just prior to a large appliance turning off, you have 200*15 = 3000 joules in "savings", as opposed to the normal 600 joules if you were running at zero. That literally gives you 5 times more time to work with. But it means 4kwh from the grid per day. Which is fine if you're not covering your full load from PV... but many of us are.

Ah, yeah. I didn't realize that. If I'm using 30-50kWh a day - it's not the end of the world. I'm still going to push to get this sorted, though. It's adding even more to the already wasted 30-40% PV output during the day. It's still a lot better than how I was sitting for 10 days paying double what I normally would for electricity with my inverter off.

Has anyone on the forum managed to get an energy diversion system working - and in a way which will pass CoC? From a physical electrical/electronic POV, how does it work and if it's a straightforward process, why do inverters not come with the functionality? Are we a minority which needs it?

Quote:

Quote

For the mains section, the choices are:

    a home-built switch principally comprising a trigger IC, triac and heatsink, or
    a commercially produced solid-state relay.

How would the relay even work? Is a solid state relay and its controller able to react fast enough to divert when the current flow is reversed and then switch back to mains without any noticeable affect? And then there's the fact that it's another link in the possible-failure chain.

2 hours ago, Charl_CCU said:

Thanks for nothing DA. Why do they have this stance whereas in CoCT they are embracing it and even offering feedback at reasonable rates. I wonder if they really are experiencing technical challenges or if that is another cover-up story.

I'm not sure it is the DA per se.

The DA has been the majority party in CoCT for a long time now allowing them (the DA) more "freedom" to move on real issues and changes. 

COT and COJ on the other hand has tasted some DA influence yes, a teeny weeny amount, but not nearly enough to make any real changes.

Therefor the "technical issues" I read as being "political motivated issues". I mean, does anyone see the ANC / EFF allowing more affluent people to take away their income? COT / COJ has done their studies on the "loss in income" they will face if they allow solar systems. 🙂 

From a article I read a while ago CoCT wants to be self reliant ito electricity, not be  beholden to Eskom, in order to attract more international investment to Cape Town. A city is the same as a rather large business. Needs income to be able to operate and expand.

So this is politically motivated I would hazard to guess.

Good news is I recon CoCT is the pilot site for SA and the only Munic currently in court to challenge the law so that they can buy power from other sources than Eskom. So when all is said and done, NERSA and my bud Rama (Cyril) is on board, law has changed too, things may change faster for the rest is my 2nd guess.

Till then reduce your consumption and give them a huge f__ff and go "off-grid". That's what I would have done ... at the very least I would have left the evening loads on Eskom (kitchen), the rest I would have taken off-grid.

Edited May 28, 20197 yr by Guest

54 minutes ago, The Terrible Triplett said:

...

I skimmed over that study - which was really long. It is still really silly. It's like asking the oil industry doing a study to see if they will lose money if EVs become popular.

I wish I could have used this opportunity to go off-grid but unfortunately it just doesn't make sense ROI-wise with the current battery prices. Especially considering that I don't see myself living at my current address for longer than 5 years.

Edited May 28, 20197 yr by Charl_CCU

Ja, going off-grid is not that easy. But like I said, if I was pushed, I'll keep the kitchen on the grid, rest I take off.

BUT, one must be wise.

8 minutes ago, Charl_CCU said:

Especially considering that I don't see myself living at my current address for longer than 5 years.

You can always take it all with you. Nothing says you must leave it behind.

Any case, just thought I share my thoughts on the matter. Be wise!

2 hours ago, Charl_CCU said:

Are we a minority which needs it?

I think so. I'm not aware of any other country that is so scared of a few kilojoules of energy going into their grid. Energy as small as that will hardly make it to the end of the street (presuming an urban area), let alone to the local transformer, let alone a substation or the high voltage transmission system.

Just now, The Terrible Triplett said:

Ja, going off-grid is not that easy. But like I said, if I was pushed, I'll keep the kitchen on the grid, rest I take off.

BUT, one must be wise.

You can always take it all with you. Nothing says you must leave it behind.

Any case, just thought I share my thoughts on the matter. Be wise!

Thanks a lot for your input - I appreciate it. I really wished I could've gone off-grid.

I suppose you are right that I can take my battery with me. But again, there is the practical POV that it doesn't make sense to spend that amount of cash on a battery right now.

2 minutes ago, Coulomb said:

I think so. I'm not aware of any other country that is so scared of a few kilojoules of energy going into their grid. Energy as small as that will hardly make it to the end of the street (presuming an urban area), let alone to the local transformer, let alone a substation or the high voltage transmission system.

Ah yeah, it is still really annoying. Maybe people would abuse it somehow to cause chaos/damage - I'm not sure. Then again, our population is known for some not-so-safe/compliant electrical systems. Especially when it comes to load shedding. I've seen some really unsafe installations and also a lot of cheap DIY kits going around back then.

6 hours ago, The Terrible Triplett said:

I'm not sure it is the DA per se.

Yeah, about that. When the water thing hit Cape Town, we were continually reminded that the city and the political party are separate entities, and to a great extent the political guys do leave the city guys to run their own affairs. And that is a good thing, constant interference would be just as bad, so one should be careful what you wish for when you do ask for more political influence . Admittedly of course, one does expect the opposition to be a bit more "progressive"... so the disappointment it is understandable.

("Progressive" in double quotes, because it is one of those vague terms thrown around in politics and moral philosophy. Progress presupposes that you know where you are going... often we don't).

5 hours ago, Coulomb said:

'm not aware of any other country that is so scared of a few kilojoules of energy going into their grid.

I don't think that's the main problem. The main problem is that electricity theft and meter tampering is so rife. I do prefer the approach where the meter just bills you for reverse flow (so much simpler and gets the same job done), but for some reason the meter makers all add this reverse-detection feature now. The Landis guys at least gives you a very wide margin...

Hi Gents

Can the below product perhaps work on SA geysers.If so it might just do the trick.

https://www.earthwiseproducts.co.uk/product/solic-2000/

 

Thanks for al replies.

 

On 2019/05/28 at 2:24 PM, plonkster said:

 

3. Run with a high grid setpoint. Let me explain. Many inverters have a "setpoint", so instead of aiming for zero, you can tell them what power level to aim for. You might set this to 300W for example, then it will always use 300W from the grid and the rest from solar. The downside is you cannot lower your bill below this point. The upside is that there is an extra buffer of positive energy that has to be surpassed before the meter trips, which may give you a couple extra seconds and prevent tripping.

 

How will the above option be implemented on an Infinisolar inverter?

11 hours ago, Frodo said:

How will the above option be implemented on an Infinisolar inverter?

I had a quick scan through a few manuals, and I don't think that they have this facility. You can set the maximum feed-in power, but they don't say if you can set it as low as zero or negative, as you'd want here. Nor is there a clue as to the resolution. It seems that with some models, you have to use SolarPower or other suitable monitoring software (ICC presumably doesn't handle them); there doesn't seem to be any settings via the LC Display.

Some models (e.g. Infini V series) only seem to have a grid feed-in enable/disable setting: setting 09 to Grd ("Solar or battery energy to grid disable").

Hopefully actual owners (I'm not one) who have figured this out can comment with better specifics.

I had the first trip since the "fix" today. I hope it wasn't the meter. I really don't want to have to increase the import minimum to 300w.

Also, I topped up my new meter for the first time today with my Standard Bank online banking app. I tested it out with R100 and got almost R2.5/kWh. How does this make sense? Does SB put a big fixed/percentage based commission on the purchase?

17 hours ago, Charl_CCU said:

Also, I topped up my new meter for the first time today with my Standard Bank online banking app. I tested it out with R100 and got almost R2.5/kWh. How does this make sense? Does SB put a big fixed/percentage based commission on the purchase?

A neighbour of mine was complaining about being overcharged by Standard Bank earlier this week (Cape Town).  I topped up with FNB yesterday and the charge was the same as usual.

I don't believe it would be legal for SB to take a commission on electricity sales, it is more likely to be some sort of billing system snafu.

Just something to check guys. I believe the amount that the seller is allowed to make from an electricity sale is worked into the price and they are not allowed to charge a fee on top. So it is unlikely that a bank would be dumb enough to do this. What I have seen is that some mom-and-pop shops or filling stations will have a minimum amount that you must buy, especially when using a card, otherwise the amount they get out of it does not cover their transaction cost and they actually lose money.

At this time of year, as we move into winter, you have to remember that above 600kwh electricity does cost around R2.56/kwh. That's what everyone pays once they go over their respective limits (350kwh for lifeline people, 600kwh for the rest of us). So work out what you paid, and it if happens to be R2.5575/kwh, and you believe you are not in block 2 yet, you'd have to take it up with Cape Town themselves I believe.

Also, buy some electricity tomorrow (1 June) and see how much you pay then. It will be either R2.10 or R1.85 depending on what tariff you are on.

For years I used to educate people on a particular local facebook group how the pricing structure works... because lots of people are running around claiming you have to buy all your electricity in one block because the price goes up... and no matter how many times you explain it, some idiot will still sell that nonsense as gospel truth 🙂

Also... every month I buy at least R1112 of electricity. On the last day of the month, if I've spent less than R1112, I go and buy the remainder before the new month. I buy as much of the cheap electricity as I can, because in winter I use more than 600kWh a month, and then the amount that I "banked" on the meter comes in handy. Unfortunately I usually run out of cheap electricity around the middle of May. We'll see how it goes with the new Pv modules I installed only in March (so they did not yet have a whole year's impact).

So how does that work, you make sure you have bought as much cheap rate electricity as you can, and store it in the meter? I wouldn't like to be your tax accountant! LOL.

Edited May 31, 20197 yr by DeepBass9

6 minutes ago, DeepBass9 said:

and store it in the meter?

Yeah, it's a bit of a hilarious concept to this Aussie too.