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Low grid voltage?


Bobster.

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5 minutes ago, Bobster said:

My neighbour just called. Load shedding has ended and he's getting 189V coming in.

There is something flawed about the idea of load shedding. Sure, the load goes down when an area is shed, but when the power comes back on, all those geysers and fridges work overtime to catch up, and lots of people are charging batteries to cover the period when the power was out. You're just relying on the poor people who can't afford UPS systems and/or solar.

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41 minutes ago, Bobster said:

When my neighbour called it was 219 and now it's climbed to 227. Is this the inverter matching grid input? 

Yes. The inverter can't make a measurable difference to the grid. So if the grid is 215 V, you can push it locally to say 216 V, but out on the street it's still 215.01 V.

If the grid is 189 V, then the inverter probably makes the decision that it's not going to connect to that, because who knows how it's going to behave.

At least, that's my understanding, having worked in a toy microgrid for several years.

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22 hours ago, Bobster said:

My neighbour just called. Load shedding has ended and he's getting 189V coming in. 

What do hybrid systems do in such cases? It seems to me there could be problems if the grid is 189v and my system is trying to export something else. 

I had 190v coming in during Sunday's window of loadshedding, and it went back to ~220 after the loadshedding window. So technically I wasn't "shed". Had the same ~190v low's this morning around 6am too.

I have an Axpert King, and I'm not 100% sure what the inverter does, but it does seem to augment to the low voltage with battery. Whether it's using the battery exclusively or not is a good question.

Edited by TheRoDent
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32 minutes ago, TheRoDent said:

I had 190v coming in during Sunday's window of loadshedding, and it went back to ~220 after the loadshedding window. So technically I wasn't "shed". Had the same ~190v low's this morning around 6am too.

I have an Axpert King, and I'm not 100% sure what the inverter does, but it does seem to augment to the low voltage with battery. Whether it's using the battery exclusively or not is a good question.

When I used to have an inverter it certainly did that. Every now and then I'd hear it switch on and then shortly thereafter off, which I assumed was a brown out rather than black out (because non-backed up circuits kept working).

@Coulomb's explanation, for the type of system I have now, makes sense. Otherwise it may be getting 190 in and trying to export 230, and also because I might have 190 on part of the DB and 230 on the rest, which doesn't sound like a very good idea.

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23 hours ago, Coulomb said:

There is something flawed about the idea of load shedding. Sure, the load goes down when an area is shed, but when the power comes back on, all those geysers and fridges work overtime to catch up, and lots of people are charging batteries to cover the period when the power was out. You're just relying on the poor people who can't afford UPS systems and/or solar.

Indeed. Though my conscience is clear because my house keeps running of batteries and either

a) the batteries will recharge from solar (not grid) if the sun is up
b) we have enough battery to get us through a night and then they start charging again in the morning.

But the general point is a good one. 

The City talked about another method they were employing, but there's suspicion that all they were doing was talking about it. This was to use smart meters (which are now common in Johannesburg) to limit draw on a property by property basis. EG They can remotely set the meters to, for example,  15A and if you draw more than that the meter will first warn you by switching off and on a few times, and then, if you don't respond, disconnecting you for, say, 30 minutes and leave you to consider things. That seems a better way of doing things - get people to cut consumption but still be able to keep the lights on and the beer cold.

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