Brown outs at night

RonSwanson said:
OK. I will log a ticket with Sunsynk.
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Grid-tied inverter. They try to follow mains frequency, which is how they push power back into the grid. I still think the spikes are an error, otherwise you would have a smoking wreck due to phase mismatch.

P.S. My cousin had a burnout recently. Turned out to be a software error.
 
Jaws677 said:
Yip.

All the Eskom Coal fired power station have generators that are all synchronised and all rotate at exactly 3000 rpm. The steam turbine shaft and generator shaft are connected as one shaft.

If you look at Kusile with each unit rates at 850 MW you can imagine that the whole rotating assembly is a hefty affair spinning at incredible speed.

Now all these spinning shafts are connected electrically, but if one should go out of synchronisation and the main breaker of the generator is not disconnected in time that shaft will dislodge itself and land somewhere in a Mielie field.

And yes this has happened.

Voltages deviations are expected in any electrical network. Frequency deviations not so much.

Voltage dips) are due to overload of the transmission and distribution systems ( cables and transformers)

A dip in frequency would indicate an overload in generation ability and hence why we have load shedding. You need to shed load before the grid frequency goes down otherwise you lose the entire grid.
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There can be small differences in frequency if you consider the speed of light is finite, and the generators are geographically dispersed, both from each other and from the consumer. This should all be covered by the 1% tolerance margin (0.5Hz) up or down, depending on current flow direction.

There was an episode of long-term grid frequency degradation in Europe, as one small country refused to generate power, and just 'stole' from the grid. Clocks started to run several minutes a day slow:
www.bbc.co.uk

Kosovo-Serbia row makes Europe clocks go slow

A dispute between Kosovo and Serbia is slowing down alarm clocks across 25 countries, operators say.
www.bbc.co.uk www.bbc.co.uk
 
Jaws677 said:
That is impossible. There is absolutely no way for the Eskom grid frequency to deviate from 50 Hz.
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Any fluctuations in voltage or frequency is due to a fault with the transformer (on the poles on the streets) ?
 
The_Traveller said:
Any fluctuations in voltage or frequency is due to a fault with the transformer (on the poles on the streets) ?
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Not quite. Voltage faults are most likely to be local, but can also be regional or grid-wide.

Edit: Street transformers have a limited ability to stabilise the voltage when there are grid fluctuations. The CoCT has been upgrading the supply over many decades. You may be living in an area where the transformer is rather old, and this tap-changing function is less reliable. Note that these voltage corrections take time to act, and are not spike (or sag) preventors.

Transformers cannot change the AC frequency, you need a switch mode power supply to do that.
 
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zeridine said:
Ive experienced incoming grid electricity running at 40.8Hz in gauteng in the past. Everything was buzzing with clocks losing time. Dont expect too much of your grid electricity if you do have the luxury of said electricity.
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Yup. Very few on this forum want to believe anyone who reports frequency instability in GP. I too have seen frequency variations + and - .
 
Gordon_R said:
Measurement error. If those spikes were real, there would have been a meltdown of the grid. Deviations of more than 0.5Hz result in blackouts.
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No they don't. But they do all sorts of things to everyone's equipment. Sustained over hours, it might. This values posted by Ron are pretty much what I also measured.
 
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Jaws677 said:
That is impossible. There is absolutely no way for the Eskom grid frequency to deviate from 50 Hz.
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Not impossible. Variations are experienced all the time.
The old standard was +/- 0.5 Hz. Don't know if Eskom still adheres to that standard. I will post the UK standard, and it will surprise you!
 
Geoff.D said:
And you might need a pretty sophisticated instrument to detect and measure the transient. That same transient might be sufficient to trigger the charging/discharge cycle for long enough to trigger alarms.
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Geoff.D said:
Yup. Very few on this forum want to believe anyone who reports frequency instability in GP. I too have seen frequency variations + and - .
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I'm not sure how to reconcile those two statements. Either you have incredibly sophisticated equipment at home, or you rely on a device which may be fooled by transient spikes into assuming an AC phase change that did not actually occur, and reports a frequency different from 50Hz.

Given the length of SA's transmission network (as per my previous post), minor grid fluctuations are guaranteed. By contrast, major frequency fluctuations would result in current flowing in the 'wrong' direction, producing instability and blackouts. This probably isn't the right thread for such a detailed discussion...
 
Gordon_R said:
I'm not sure how to reconcile those two statements. Either you have incredibly sophisticated equipment at home, or you rely on a device which may be fooled by transient spikes into assuming an AC phase change that did not actually occur, and reports a frequency different from 50Hz.

Given the length of SA's transmission network (as per my previous post), minor grid fluctuations are guaranteed. By contrast, major frequency fluctuations would result in current flowing in the 'wrong' direction, producing instability and blackouts. This probably isn't the right thread for such a detailed discussion...
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I used to have access to the right equipment to measure with. I no longer have and and have not been able to undertake any measurements during LS periods.
We don't as users know when and how often complete areas with their own generation capacity are isolated from the grid.
What happens when say for example, the old Kelvin or Isando power station in JHB is brought on line?
I know what the correct procedure is to connect it to the grid, but do you have any faith that the correct process is followed?
I don't.
I won't believe for one ms that all the LS switching is not causing all sorts of spikes and we won't as users know unless we are measuring all the time.
 
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Gordon_R said:
I'm not sure how to reconcile those two statements. Either you have incredibly sophisticated equipment at home, or you rely on a device which may be fooled by transient spikes into assuming an AC phase change that did not actually occur, and reports a frequency different from 50Hz.

Given the length of SA's transmission network (as per my previous post), minor grid fluctuations are guaranteed. By contrast, major frequency fluctuations would result in current flowing in the 'wrong' direction, producing instability and blackouts. This probably isn't the right thread for such a detailed discussion...
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Is a grid-tied inverter, whose function it is to synchronise with the grid, not incredibly sophisticated enough? :rolleyes:
I'll have to log another ticket with Sunsynk.
Note that the times of flatlining at 51.9 Hz were during loadshedding.
 
AlphaJohn said:
Not always. Brown outs can also be power spikes.

Spike brown outs claimed many a equipment in my life, not a fan :D
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Voltage spike.


:p

Fortunately for those the surge protector should help? It is the voltage drop that we have massive problems with.

The other day it was so bad that some equipment worked in the house and others didn't. Turned out to be the transformer to the complex phasing, a fuse blown and apparently only one phase of the 3 phase was running (y'all I don't know how it works) , which turned out to trip the substation after the fuse was replaced, which turned out to be an issue at the main station.
 
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I was also experiencing this. Fan would stop spinning in the middle of the night/lights would flicker. I ended up finding a plug that had a weak connection, it was making a funny sound. After bending the plug terminals a little bit closer to give it better contact, and double checking that everthing in my kitched was plugged in all the way (fridge was a little bit loose) the problem seemed to stop.
 
crysis said:
I was also experiencing this. Fan would stop spinning in the middle of the night/lights would flicker. I ended up finding a plug that had a weak connection, it was making a funny sound. After bending the plug terminals a little bit closer to give it better contact, and double checking that everthing in my kitched was plugged in all the way (fridge was a little bit loose) the problem seemed to stop.
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There are all kinds of electrical gremlins that can cause those kinds of symptoms. Edit: A bad plug should not cause ceiling lights to flicker (separate circuit breaker), the real problem is further upstream.

In my case it turned out to be bad contacts in the main 60A circuit breaker in my DB (50 years old). I don't think this was what the OP was complaining about, but there can sometimes be multiple factors involved.
 
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Gordon_R said:
There are all kinds of electrical gremlins that can cause those kinds of symptoms. In my case it turned out to be bad contacts in the main 60A circuit breaker in my DB (50 years old). I don't think this was what the OP was complaining about, but there can sometimes be multiple factors involved.
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Yes, it is pretty normal to find wall sockets that over many years wear and tear will start resulting in poor contacts.
No this is not the issue highlighted by OP.
 
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