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Load shedding


Bobster
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Recently, in another thread, @Coulomb said

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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.

Well I think it goes further than that now. 

When load shedding started, it was hard to know when it would strike and for how long. These days we all have apps on our phones, and neighbourhood whatsapp chats, and the municipalities publish load shedding schedules and so we start anticipating the load shed.

My suburb starts shedding at 12:00 today. So what happened this morning? Everybody got the lawn mowers out and got their grass cut and all the appliances got used in the early morning. Apps showed momentary peaks of 5 kw in our house and sustained runs at 3kw. Since I am a boring fellow who loves watching SEMS portal, I can tell you that this is high for our house. What was happening was that the wife and housekeeper were trying to get the dishes clean, the ironing done etc before the shed starts.

What @Coulomb and I were discussing is heavy loading after restoration of power. Some properties in my street were reporting under 200 V incoming. This slowly crept back to normal. So what had happened was that City Power turned us back on and everybody's geyser and everybody's deep freeze and lots of people's UPS all started drawing current at the same time. 

So now, I think, we get two peaks - one just before load shedding and one after.

So does the strategy actually save anything? Well... I guess it must because the grid hasn't fallen over yet. But I wonder if it's not a game of diminishing returns. Which would mean that Eskom are going to have to go to a higher stage as we get better at mitigating against load shedding.

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19 minutes ago, Bobster said:

But I wonder if it's not a game of diminishing returns.

I've thought about this too. You should also consider this from the point of a municipality. They need X amount of energy to pump water into reservoirs. Past a certain stage... the pumps are simply running 100% of the time that energy is available, and the average consumption must necessarily creep up.

Additionally, those with PV modules might start charging from the grid at higher stages of load-shedding, especially those with smaller setups, to keep the batteries at a higher SOC.

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It's common knowledge to those who implement load shedding that there's this tidal wave of demand that the grid has to cope with when the power resumes.

This doesn't imply there's no savings to be had. There are many users who are clueless about their power consumption. So during load shedding all the unnecessary loads are also disconnected from the grid as well. Then there are the delinquent municipalities (and their equivalent clients) who aren't paying for electricity so one can only imagine what loads they have connected!

In my opinion the smart way to manipulate users power usage to a different time (to avoid peaks) is to  provide an incentive such as a reduced price for doing that.  

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34 minutes ago, Bobster said:

So does the strategy actually save anything?

I was also wondering what are they actually saving. Is Eskom actually trying to save their own cash flow from buying less Diesel. Especially if you buy diesel for customers who do not pay for the use of this service. It might make political correct sense to implement load-shedding and stay away from power cuts.

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13 minutes ago, plonkster said:

I've thought about this too. You should also consider this from the point of a municipality. They need X amount of energy to pump water into reservoirs. Past a certain stage... the pumps are simply running 100% of the time that energy is available, and the average consumption must necessarily creep up.

I see a similar problem already with water.

If like me, you happen to live in a high laying area, pumps are also used to keep your taps at pressure, of course our municipality is so bad at maintaining this pump that for the past 3 years (I have only lived here for 3 years) its steadily gotten worse we now only have water for around 6 hours a day, and some days not at all. (Our record last year over December was 8 days!)

So everyone in my neighborhood does have a 5000L holding tank to carry us through. (See our tanks as batteries and the Municipal pumps as the grid)

Instead of the municipal pump coming on and only getting everyone's homes back to pressure, we are all putting massive strain on it by refilling our tanks (I mean we are not going to go without water), so when it is actually working it is being pushed to 100% capacity for hours, and so the vicious cycle repeats.

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49 minutes ago, Bobster said:

Some properties in my street were reporting under 200 V incoming.

I remember way back when I worked for Eskom when we still switched 22KV lines back manually we would monitor the amp, volt and kvar meters as customers, loads came back on, and had to sometimes quickly switch off the breaker as those big industrial loads and pumps caused haywire on those meters and you could hear the stain on transformers and switching of capacitor banks to try and cope with loads. We had the old experts (oomies in khakie)who timed things and switch on-off up to about four times by the fourth time those pumps starting currents were little less as motors started getting motion and it could be seen on the amp meters. These days I think it all works on auto from the control room and if the protection settings were not set correct we see things blow up.

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21 minutes ago, Gerrie said:

Is Eskom actually trying to save their own cash flow from buying less Diesel.

I think there are two things that are being managed. The first is the peak power use. Once you have power stations tripping, you get the domino effect that could trip the whole grid, so this one is arguably the most important one.

The second one is the total energy use. You can only generate so much kWh in a day, and you need to keep some of it spare for 1) contractual obligations to SAPP, Southern African Power Pool, 2) replenishing pumped storage ahead of peak times, 3) saving on Diesel costs. This is why we have load shedding in the early hours of the morning and on weekends while one would expect plenty of spare capacity: that energy is needed for these things.

When considered in order of priority, I suspect saving Diesel is the last item on the list, outdone by peak management, contractual obligations, and pumped storage.

It's from this second set of parameters (the non-peak ones) where you will see the greatest amount of diminishing returns.

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Today some fool indicated on the radio that eskom are charging ...using an example ...R6 for a R10 service and should increase the price to what everyone else around the world is paying for electricity... Eskom can no longer charge a reduce rate ...they should be charging their worth ...like everything in this country ...you can only smile and say ....eeeeish. 

 

 

 

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3 hours ago, plonkster said:

1) contractual obligations to SAPP, Southern African Power Pool, 2) replenishing pumped storage ahead of peak times, 3) saving on Diesel costs.

I guess you could also ad a 4) Keeping capacity spare in case of a unplanned unit trip, preventing entire grid collapse. 

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I knew a colleague who was a senior engineer at Eskom and I witnessed how they monitor the status of the grid: There is an automated SMS that is sent out to all concerned that is generated by all the power stations around the country.

The key indicator in this report is the frequency of the generation equipment. As the frequency slips down it triggers the alarm for the management to do something!  

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23 hours ago, Richard Mackay said:

It's common knowledge to those who implement load shedding that there's this tidal wave of demand that the grid has to cope with when the power resumes.

This doesn't imply there's no savings to be had. There are many users who are clueless about their power consumption. So during load shedding all the unnecessary loads are also disconnected from the grid as well. Then there are the delinquent municipalities (and their equivalent clients) who aren't paying for electricity so one can only imagine what loads they have connected!

In my opinion the smart way to manipulate users power usage to a different time (to avoid peaks) is to  provide an incentive such as a reduced price for doing that.  

COJ say that they have that capability. At the moment all they offer is a seasonal tariff - you pay less in the summer, more in the winter. But in theory they can impose time of day pricing.

The trouble is getting people to understand the strategy and respond to it. I am amazed by the number of people I know who 

  1. Have converted to pre-paid electricity
  2. Think that COJ charges you differently at different times of the month.

The truth is that there's a sliding scale. The first 350 units you buy in a month are the cheapest. Then 351 to 500 costs a little more and so on. Because they feed their meter a little bit each week they see less units for their money as the month goes on and just assume that COJ are changing tariffs as it suits them (which they may not do) or changing tariff according to the date in the month (which they may not do).

My point is that even where there is a system, people don't bother to understand it or even know it's there, or the news doesn't get to them.

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I think we would all be the wiser if we could be privy to the 'gaanings aan' in Eskom's control centre.  If one had the strength to follow all the issues you would get a thorough (and scary) insight into the state of the utility.

What disillusions me is that I believe they aren't recruiting the best brains that are available to get on top of the situation.

Edited by Richard Mackay
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On 2020/02/22 at 12:07 PM, Bobster said:

Think that COJ charges you differently at different times of the month.

Oh my goodness... I've had the same thing in Cape Town, on the local Facebook "info group".

(I left that group after one too many "murdered squirrel" posts. No, I don't intentionally run over squirrels, but if I did so by accident... I am NOT getting out of my car to give the guy a decent burial... and the fact that so many idiots insist that you should attempt this with a wild possibly lice infested rodent is beyond me).

Anyway... Iit's almost accepted as gospel around here that you must buy all your power in one transaction because it gets more expensive if you don't. I've actually shown people how I buy electricity in R200 blocks and the price remains the same for several transactions, only ticking up if I go over the documented limit. Roll on a few days... the same wrong advice is delivered again. Oh well...

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8 hours ago, plonkster said:

Anyway... Iit's almost accepted as gospel around here that you must buy all your power in one transaction because it gets more expensive if you don't. I've actually shown people how I buy electricity in R200 blocks and the price remains the same for several transactions, only ticking up if I go over the documented limit. Roll on a few days... the same wrong advice is delivered again. Oh well...

I know a lady who lives in a township and who pre-buys for the year every December. Which is a very expensive way of doing it. I've shown her the numbers. I've said that she should take what she would have spent and stick it in a savings account and buy a little each month and in the meantime earn some interest.  But no... Though I suppose there is some value in knowing that's done and you can forget about it for the rest of the year.

COJ's cheapest bands used to be the first 500 units (now reduced to 350). I used to buy 500 on the 1st of the month and most months we wouldn't use it. I soon built up a multi-month credit - which I still have.

Last week I bought 200 units just so that they would take a break from turning up at my front door to ask why I hadn't bought electricity in the last 6 months.

 

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19 hours ago, Richard Mackay said:

I think we would all be the wiser if we could be privy to the 'gaanings aan' in Eskom's control centre.  If one had the strength to follow all the issues you would get a thorough (and scary) insight into the state of the utility.

In this case I'm talking about COJ's tariffs, which they publish each year in advance of the increases. They even provide examples to show how the bands work and so that you can compare post and pre paid.

I follow City Power and Eskom on Twitter and seldom get a surprise when the power goes out*. If that's too much PT then one can install Eskom se Push. But no... we get regular warnings that the lights have just gone out where somebody's auntie stays and so that means we're about to be load shed again. An inability to distinguish between "outage" and "load shed" doesn't help. Factor in distrust of the authorities (after all, if they've gone to stage 2, then stage 99 is just around the corner) and suddenly you're in a world that runs on voodoo.

* I also get an insight into how much they have to deal with, especially down south where there are lots of informal settlements and cable theft. So I don't get shirty with whoever I speak to on the phone or who comes to my street because I know they're doing their best to put out a lot of fires. I reserve my ire for those a bit higher up the food chain.

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1 hour ago, Gabriël said:

well spoken!

"many a truth is spoken in jest!"

Well, in context here he's probably speaking more about that thing Arthur C. Clarke said that anything that is sufficiently advanced is indistinguishable from magic, to which you can add Plonkie's corollary, that to anyone sufficiently uninformed everything seems like magic.

But yeah... isn't it wonderful how the world is so beautifully regular that we can describe it with mathematics? That is something that many people don't even question, only the crazy philosophers seem terribly concerned about that one... 😛

 

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4 hours ago, Bobster said:

In this case I'm talking about COJ's tariffs, which they publish each year in advance of the increases. They even provide examples to show how the bands work and so that you can compare post and pre paid.

I follow City Power and Eskom on Twitter and seldom get a surprise when the power goes out*. If that's too much PT then one can install Eskom se Push. But no... we get regular warnings that the lights have just gone out where somebody's auntie stays and so that means we're about to be load shed again. An inability to distinguish between "outage" and "load shed" doesn't help. Factor in distrust of the authorities (after all, if they've gone to stage 2, then stage 99 is just around the corner) and suddenly you're in a world that runs on voodoo.

* I also get an insight into how much they have to deal with, especially down south where there are lots of informal settlements and cable theft. So I don't get shirty with whoever I speak to on the phone or who comes to my street because I know they're doing their best to put out a lot of fires. I reserve my ire for those a bit higher up the food chain.

I realise this is counter to an earlier point that I made about people getting organised and anticipating load shedding. When I made that post it was a work day  but I was at home on leave. Seems the gardeners and the housekeepers either got organised or anticipated rain (which was forecast) because just after the shedding started the actual owners started whatsapping to find out what is going on.

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1 hour ago, plonkster said:

Well, in context here he's probably speaking more about that thing Arthur C. Clarke said that anything that is sufficiently advanced is indistinguishable from magic, to which you can add Plonkie's corollary, that to anyone sufficiently uninformed everything seems like magic.

Lol. I was speaking more about Plonkie's corollary actually. 

 

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2 hours ago, plonkster said:

But yeah... isn't it wonderful how the world is so beautifully regular that we can describe it with mathematics?

THE SIMULATION IS REAL :P

Veritasium did a excellent video recently about the Mandelbrot set, and it blew my mind.

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23 minutes ago, PJJ said:

Mandelbrot set, and it blew my mind.

there are a few good ones out there - it does blow the mind, you're right; and to be conscious of the fact that although they seem all similar they are all different... snowflakes, fingerprints, you name it... eternity comes to mind and then ... phew

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6 minutes ago, PJJ said:

THE SIMULATION IS REAL :P

It's actually not a completely nuts idea. Some really clever people think it might have some warrant:

https://www.extremetech.com/extreme/227126-neil-degrasse-tyson-says-its-very-likely-the-universe-is-a-simulation

Of course (just like with Panspermia), that just pushes things back another level, raising even more questions. It's fun thinking about it though.

 

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2 hours ago, plonkster said:

But yeah... isn't it wonderful how the world is so beautifully regular that we can describe it with mathematics? That is something that many people don't even question, only the crazy philosophers seem terribly concerned about that one... 😛

It is the gift that Newton left for us. Before Newton the world was chaotic and unknowable. After Newton the world was understandable and ran according to principles that are consistent and which can be fathomed and written down (part of what he left us is a language for describing these laws). 

Even if we don't know the specific laws (but wasn't everybody taught at school, for example,  that for every action there is an equal and opposite reaction?) we should remember the general principle and apply it and then we can know stuff and the world gets a little less chaotic.

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4 minutes ago, plonkster said:

Of course (just like with Panspermia), that just pushes things back another level, raising even more questions. It's fun thinking about it though.

you are enticing me to be reprimanded again on this forum... all i can say is it is great to have answers to the most important questions...

which reminds me, who might be able to help me with back to utility voltage settings for the pylontech in order to not exceed say 50% soc?

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