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Voltage low after load shed


Bobster
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I've been watching my Goodwe since power came back on. 

The voltage is low and the Goodwe is matching that.

Shortly after restoration the reported grid voltage was under 190.

I presume that City Power don't have to spin up a generator so why is the voltage so low? Geysers and motors all turning on at the same time? 

Since you ask, no, I don't know what a "normal" voltage is. 

Screenshots_2021-01-15-20-48-27.png

Edited by Bobster
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11 hours ago, Bobster said:

I've been watching my Goodwe since power came back on. 

The voltage is low and the Goodwe is matching that.

Shortly after restoration the reported grid voltage was under 190.

I presume that City Power don't have to spin up a generator so why is the voltage so low? Geysers and motors all turning on at the same time? 

Since you ask, no, I don't know what a "normal" voltage is. 

 

I presume you have measured the incoming voltage and the inverter tallies with this reading?

Check the voltage of your neighbours (near and far) in the same LS zone as you...

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1 hour ago, Richard Mackay said:

I presume you have measured the incoming voltage and the inverter tallies with this reading?

Check the voltage of your neighbours (near and far) in the same LS zone as you...

Hi Richard, I didn't actually take my multi meter and measure it. 

The street is split into three electricity wise, which I assume is 3 phases. 

1) Street lamps

2) North half of the street

3) South half of the street

This may be the same in surrounding streets. 

It is an old gripe in our street that the North half always switches on before the South, but I am thinking that maybe something drags our phase down, and that whilst some devices may work at that voltage, although not optimally, others decline to. EG my neighbour's fluorescent lamps. 

Also most of them don't have a system like mine that will give them a reading nor do they want to mess with a multimeter (if they have one) and mains in the dark. But there is one...

The voltage slowly climbs. The Goodwe switched over at 200v (which it has to match) which took about 30 minutes. It took about 90 minutes to get into the 220s. It did eventually get to 229.

We have shedding again this morning, and so I will be able to take a measurement. 

But is this what everything turning on again can do? 

Edited by Bobster
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2 minutes ago, Bobster said:

But is this what everything turning on again can do? 

Definitely not! This sounds like the grid in Zimbabwe..

Try and measure the other phases. Also if you can locate your local transformer and feel the heat from it (and from what distance)

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2 hours ago, Richard Mackay said:

Definitely not! This sounds like the grid in Zimbabwe..

Try and measure the other phases. Also if you can locate your local transformer and feel the heat from it (and from what distance)

It's just happened again. City Power came back on at 189v. I checked this with a multimeter at the main breaker. 

There is anecdotal evidence from last night of ovens taking a long time to heat.

I walked up to what I think is the local transformer. It is humming loudly and the external casing is warm to the touch 

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17 hours ago, Richard Mackay said:

Are you supplied by City Power?

If so log a fault with them (or with the relevant utility) 

What do I tell them? Voltage is low? 

It always gets up to where it should be. It's fluctuating between 223 and 224 right now. 

I've talked to neighbours, a surprising number of whom still have incandescent lamps of various kinds. The moment the lamps come on they turn on their ovens, of course the geysers kick in, pool pumps start running - all the stuff that Eskom ask us to go easy on between 17:00 and 21:00.

I think I need to find some like minded neighbours to help with monitoring. 

But I also expect nobody to prioritise this. After all, we do actually have power. 

But maybe... 

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22 hours ago, Richard Mackay said:

Definitely not! This sounds like the grid in Zimbabwe..

Our situation here in Zim every evening at peak demand in the evening, power all the way down to 165v due to us being on an overloaded transformer. 

Saying that my Must inverter seems to handle it fine in 3 years of use, passes through the low voltage so appliances take stress, however I have no doubt that it is not good for it 

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21 minutes ago, Brani said:

i would for safety reason try to avoid switching on the inverter unless the incoming voltage is around 200v (+/- 10%).

My inverter won't deal with the grid until the incoming voltage gets to 200. But thereafter it tracks the grid, even if it drops below 200 again. 

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Besides the inconvenience and possible damage of your electrical equipment what is more serious is the reason why the grid voltage is so low. Most probably is that it's overloaded. To drop this amount of voltage means it is seriously overloaded. It could be the cable reticulation as well. (are you near a delinquent township?)

Definitely not a first world problem! Report it before the substation burns down and then it will be weeks before it is 'repaired'.

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2 hours ago, Richard Mackay said:

Besides the inconvenience and possible damage of your electrical equipment what is more serious is the reason why the grid voltage is so low. Most probably is that it's overloaded. To drop this amount of voltage means it is seriously overloaded. It could be the cable reticulation as well. (are you near a delinquent township?)

Definitely not a first world problem! Report it before the substation burns down and then it will be weeks before it is 'repaired'.

I meant that my personal situation is a so-called "first world problem". 

Thanks for the advice all. I am going to keep an eye on this and try to get some neighbours to do the same. 

It occured to me that there may be an abnormal load on a property in our street, but is it possible to detect that? 

As I said, the voltage always recovers, but it takes time. (226v right now)

I will report, but I think it helps if other properties confirm the issue. Also credibility and method may be attacked. 

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11 minutes ago, Brani said:

Hi Bobster,

clapm meter on each property will give you a good indication.

How much is that going to cost? And where do I fit it? Around the red conductor on the municipal side of the main breaker? I'm not an electrician. 

Ok... If I had such a device and my neighbours were helpful I could walk up and down the street and take measurements. 

Edited by Bobster
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So I have the opposite problem.

My voltage sometimes reaches 255V!

It used to be a constant 230V, but then a main substation exploded and the "fixed" it, now we are getting 245-253! The inverter logs an error when it gets too high...

How I long for a constant 230V......

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  • 4 weeks later...

I've been taking more interest than usual in grid voltage since I made this post. There are days when the voltage seems mostly ok, days when my inverter spends of lots of time disconnecting because grid voltage got down into the 190s. There seems to be a correlation with the weather. When it's overcast the low voltage is more likely, presumably because other devices are working harder and so the load on our section of the grid grows. 

So it becomes a catch 22. On the days when I am more likely to have to resort to grid, I am less likely to be able to use it because the voltage drops and my inverter disconnects.

I note that it almost never gets up to 230. It hovers around 220 on a good day. My electrician tells me that the sub stations have different taps available on the transformers and all ("all") that's required is to get city power to change to a tap on the transformer that will up the voltage. I put the word "all" in quotes because I can't see it being quite that easy, even if they acknowledge the problem and set out to resolve it. 

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On 2021/01/16 at 12:41 PM, Bobster said:

It's just happened again. City Power came back on at 189v. I checked this with a multimeter at the main breaker. 

NB. If you're a City Power customer and/or have the Itron meter, the meter actually reports the incoming voltage and you don't have to be fooling around with a multimeter.

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1 hour ago, Bobster said:

NB. If you're a City Power customer and/or have the Itron meter, the meter actually reports the incoming voltage and you don't have to be fooling around with a multimeter.

I hope my multimeter is good enough to measure voltages accurately and that I'm capable of using it so that I won't be classified as 'fooling around'. 

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On 2021/01/17 at 8:57 AM, Bobster said:

My inverter won't deal with the grid until the incoming voltage gets to 200. But thereafter it tracks the grid, even if it drops below 200 again. 

There is probably a fix for this.

Do you need the grid to power anything or is it only to fire up your inverter?? 

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6 hours ago, Richard Mackay said:

There is probably a fix for this.

Do you need the grid to power anything or is it only to fire up your inverter?? 

The trap I can fall into is that if there is load shedding coming and  there is low PV then that's when I need to have the resort of charging my battery from grid, but if the voltage is low then my inverter won't have anything to do with the grid and so I can't charge from grid. I am less worried about the circuits we don't back up (pool pump etc).

It seems to me, though I can't prove it, that grid voltage tends to drop on overcast days. 

That all said, the voltage is ALWAYS down on restoring after a load shed. So maybe the load has grown over the years.
 

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