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cuthound

National Grid Failure - Lesson to be Learnt

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1 hour ago, cuthound said:

 

As I explained in posts #3 & #12. However a battery bank wouldn't help, because the electronics needed to invert it to ac are the cause of this problem.

That's not my understanding. With a suitable inverter design a battery bank can stabilise frequency. Inverters feeding from non-synchronous sources like wind turbines are designed to feed the maximum amount of energy into the grid in steady state, they don't have the energy reserves required to feed extra energy short term, which is what's needed to support the frequency.  Battery-based frequency support systems are designed not for steady-state energy supply, but precisely to inject extra energy to support the grid when the frequency drops. Since a big battery bank can instantaneously supply a large power, that takes the place of the energy stored in the rotating mass of turbine alternators.

 

It's clear that things didn't happen as expected/designed during this event, but that allows lessons to be learned for next time. We need to learn how to run a renewable-heavy grid, not use this as some stupid excuse to not try. 

 

Incidentally, the fact that fully one-third of the total grid load was being generated by wind power is dammed impressive - I'd never have guessed it could be that high. Something to be a bit proud of.

 

MP.

 

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3 hours ago, cuthound said:

 

As I explained in posts #3 & #12. However a battery bank wouldn't help, because the electronics needed to invert it to ac are the cause of this problem.

But it works in Australia so why wouldn't they work here? Is it because we would be upside down?

2 hours ago, MoominPapa said:

That's not my understanding. With a suitable inverter design a battery bank can stabilise frequency. Inverters feeding from non-synchronous sources like wind turbines are designed to feed the maximum amount of energy into the grid in steady state, they don't have the energy reserves required to feed extra energy short term, which is what's needed to support the frequency.  Battery-based frequency support systems are designed not for steady-state energy supply, but precisely to inject extra energy to support the grid when the frequency drops. Since a big battery bank can instantaneously supply a large power, that takes the place of the energy stored in the rotating mass of turbine alternators.

 

It's clear that things didn't happen as expected/designed during this event, but that allows lessons to be learned for next time. We need to learn how to run a renewable-heavy grid, not use this as some stupid excuse to not try. 

 

Incidentally, the fact that fully one-third of the total grid load was being generated by wind power is dammed impressive - I'd never have guessed it could be that high. Something to be a bit proud of.

 

MP.

 

I agree with you and cannot wait until all electricity is produced this way

 Roll on those big wind turbines 

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2 hours ago, MoominPapa said:

That's not my understanding. With a suitable inverter design a battery bank can stabilise frequency. Inverters feeding from non-synchronous sources like wind turbines are designed to feed the maximum amount of energy into the grid in steady state, they don't have the energy reserves required to feed extra energy short term, which is what's needed to support the frequency.  Battery-based frequency support systems are designed not for steady-state energy supply, but precisely to inject extra energy to support the grid when the frequency drops. Since a big battery bank can instantaneously supply a large power, that takes the place of the energy stored in the rotating mass of turbine alternators.

 

It's clear that things didn't happen as expected/designed during this event, but that allows lessons to be learned for next time. We need to learn how to run a renewable-heavy grid, not use this as some stupid excuse to not try. 

 

Incidentally, the fact that fully one-third of the total grid load was being generated by wind power is dammed impressive - I'd never have guessed it could be that high. Something to be a bit proud of.

 

MP.

 

Does that figure include embedded wind power because, if not, you can add another 30% to wind's contribution.

 

For those who do not know, smaller turbines, such as those fitted to houses etc, do not show as a direct wind contribution to generation, but simply affect the totals by reducing the demand figure.

 

George

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10 hours ago, MoominPapa said:

That's not my understanding. With a suitable inverter design a battery bank can stabilise frequency. Inverters feeding from non-synchronous sources like wind turbines are designed to feed the maximum amount of energy into the grid in steady state, they don't have the energy reserves required to feed extra energy short term, which is what's needed to support the frequency.  Battery-based frequency support systems are designed not for steady-state energy supply, but precisely to inject extra energy to support the grid when the frequency drops. Since a big battery bank can instantaneously supply a large power, that takes the place of the energy stored in the rotating mass of turbine alternators.

 

It's clear that things didn't happen as expected/designed during this event, but that allows lessons to be learned for next time. We need to learn how to run a renewable-heavy grid, not use this as some stupid excuse to not try. 

 

Incidentally, the fact that fully one-third of the total grid load was being generated by wind power is dammed impressive - I'd never have guessed it could be that high. Something to be a bit proud of.

 

MP.

 

 

The battery man did quote his response time for the battery farm to pick up the slack...... in was milliseconds.  I'm no expert on that side of generation (we just stuff gas in at one end and the clever blokes do the rest). Battery man did also add to back up MoominP that the grid is set up for the old way of doing things and it needs to face and install the new way of doing things. Apparently there have been other near misses too.

Edited by mark99

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8 hours ago, peterboat said:

As I explained in posts #3 & #12. However a battery bank wouldn't help, because the electronics needed to invert it to ac are the cause of this problem.

I have been looking at this post with interest. The event last week was severe, but could have been much worse. The statement above is not the whole issue , however.  

 

First back to the nature of the problem and why it would not have been so severe in the past. The issue with dropping frequency in events like last week would have been resolved in the past by increased generation from power stations. In the very short term this comes from the inertia of the rotating mass of the turbine and alternator (typically a couple of hundred tones at 3000 RPM) this responds very fast. A somewhat longer response used to be provided by (mainly coal fired) stations as the boilers had a large water/steam inventory and the action of the turbine governor in response to falling frequency would be to increase steam flow, using the stored energy in the boiler to create more power. Eventually the firing rate on the boiler would increase giving a longer term response (too slow for the event last week. Current UK nuclear sites have a limited frequency response, whilst the inertia of the generator would be present, the governors on some sets reconfigured to not respond to frequency.

 

Wind turbines and solar do not respond in a similar way, they effectively have no "inertia" like the coal/oil fired stations, thus the problem last week.

 

Batteries are being added to the system specifically to help with this problem. By monitoring grid frequency (or rate of change of frequency) they can dump energy into the grid very quickly and respond in a manner similar to the "inertia" that used to be present. There are several batteries that act like this on the system, but the size/capacity is currently limited, thus they had a limited effect last week. It's likely more will be added as the system moves away from large generating sets towards more renewables. See attached for information on grid connected batteries. https://www.wired.co.uk/article/uk-power-cut-batteries-national-grid

 

Note that loss of the very large generating sets being built at Hinkley C and proposed for other nuclear sites will exacerbate the problem due to the potential sudden loss of a bigger power source than occurred last week.

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9 hours ago, furnessvale said:

Does that figure include embedded wind power because, if not, you can add another 30% to wind's contribution.

 

I don;t think so.

 

MP.

 

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11 hours ago, MoominPapa said:

That's not my understanding. With a suitable inverter design a battery bank can stabilise frequency. Inverters feeding from non-synchronous sources like wind turbines are designed to feed the maximum amount of energy into the grid in steady state, they don't have the energy reserves required to feed extra energy short term, which is what's needed to support the frequency.  Battery-based frequency support systems are designed not for steady-state energy supply, but precisely to inject extra energy to support the grid when the frequency drops. Since a big battery bank can instantaneously supply a large power, that takes the place of the energy stored in the rotating mass of turbine alternators.

 

It's clear that things didn't happen as expected/designed during this event, but that allows lessons to be learned for next time. We need to learn how to run a renewable-heavy grid, not use this as some stupid excuse to not try. 

 

Incidentally, the fact that fully one-third of the total grid load was being generated by wind power is dammed impressive - I'd never have guessed it could be that high. Something to be a bit proud of.

 

MP.

 

 

The problem is not one of speed to synchronise, but the very limited overload capacity of solid state inverters compared to rotating generators.

 

It was recognised in the critical power industry in tbe 80's and explains why most data centres use DRUPS (Diesel Rotary Uninterruptible Power Supplies) for their standby power rather than solid state UPS.

 

What is needed is something green that behaves like a rotating generator to support the short term overload, perhaps large flywheel UPS's.

 

 

Edited by cuthound
Clarification

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1 minute ago, cuthound said:

 

The problem is not one of spped to synchronise, but the very limited overload capacity of solid state inverters compared to rotating generators.

 

It was recognised in the critical power industry in tbe 80's and explains why most data centres use DRUPS (Diesel Rotary Uninterruptible Power Supplies) for their standby power rather than solid state UPS.

 

 

The data centre I worked at had a battery bank and inverter setup that could easily handle the total load. It had diesel generators too, not to handle the load, but to provide power for outages longer than the very limited runtime of the battery bank.

 

MP.

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Longer term, the solution to this lies in the load side as much as the generation side. We have to move consumers away from the idea that the grid is an infinite supply of power that's always available, and take advantage of control and communications that didn't exist when the electricity supply industry was starting out.

 

Incidentally, most boaters and other off-grid livers already think like this.

 

As an example, imagine if all fridges and freezers had an internet connection, over which that could be commanded to shut down for a couple of minutes. That would provide the ability to load-shed a huge chunk of power over a minute or two, without compromising the function of the fridges at all. Same thing applies to EV chargers: in fact maybe that should be part of the spec for those now. Fridges last a long time, so it would take years to increase the stock of intelligent ones, the population of EV chargers is going to increase rapidly over the next decade.

 

MP.

 

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3 minutes ago, MoominPapa said:

The data centre I worked at had a battery bank and inverter setup that could easily handle the total load. It had diesel generators too, not to handle the load, but to provide power for outages longer than the very limited runtime of the battery bank.

 

MP.

 

Yes that is the older way of doing it. Nowadays many data  centres, certainly the larger ones, use DRUPS to supply the whole site, even though they are less efficient and cost more to maintain for three reasons.

 

1. Much higher short term overload capacity,

 

2. Higher outputs available, the largest site I worked on had 60 2MVA DRUPS supporting the site  and,

 

3 the DRUPS is a cleaner output with fewer harmonics and doesn't corrupt the incoming supply.

 

Battery UPS systems are often used as well for each data hall for additional resilience.

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4 minutes ago, cuthound said:

 

Yes that is the older way of doing it. Nowadays many data  centres, certainly the larger ones, use DRUPS to supply the whole site, even though they are less efficient and cost more to maintain for three reasons.

 

1. Much higher short term overload capacity,

 

2. Higher outputs available, the largest site I worked on had 60 2MVA DRUPS supporting the site  and,

 

3 the DRUPS is a cleaner output with fewer harmonics and doesn't corrupt the incoming supply.

 

Battery UPS systems are often used as well for each data hall for additional resilience.

Now I think about it, the engineering dept did install a gas-fired IC generator set. Maybe for this reason.

 

For grid use, the inverters would have to be more like the stuff at the end of HVDC lines. They've just built one in North wales with an output of 2.2GW, so it is possible.

 

MP.

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Yes, if you look at how a typical UPS deals with an overload, it transfers the load to the mains to deal with it, via its static switch. 

 

As I say this isn't a new problem to the critical power world but obviously is to the national grid. Check out sub transient reactance.

 

In the short term it will be rectified by not going below a certain percentage of "rotating" capacity in the grid power make up. Longer term will require different technology or localy generated energy (although that brings another set of issues) rather than a grid.

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20 minutes ago, MoominPapa said:

Longer term, the solution to this lies in the load side as much as the generation side. We have to move consumers away from the idea that the grid is an infinite supply of power that's always available, and take advantage of control and communications that didn't exist when the electricity supply industry was starting out.

 

Incidentally, most boaters and other off-grid livers already think like this.

 

As an example, imagine if all fridges and freezers had an internet connection, over which that could be commanded to shut down for a couple of minutes. That would provide the ability to load-shed a huge chunk of power over a minute or two, without compromising the function of the fridges at all. Same thing applies to EV chargers: in fact maybe that should be part of the spec for those now. Fridges last a long time, so it would take years to increase the stock of intelligent ones, the population of EV chargers is going to increase rapidly over the next decade.

 

MP.

 

This thought has been running through my tiny brain as I have been reading this thread .. why don't home owners also look to battery power as a backup

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21 minutes ago, cuthound said:

 

As I say this isn't a new problem to the critical power world but obviously is to the national grid. Check out sub transient reactance.

 

I have been waiting years for 2 Axis generalised machine theory to appear on CWDF!  The full Kron tensor approach , please.

 

 

Chris G

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13 minutes ago, KevMc said:

This thought has been running through my tiny brain as I have been reading this thread .. why don't home owners also look to battery power as a backup

 

Because until now, there has been no need!

 

As a kid we had regular power cuts (as a lot of people living in countryside locations still do, although this is not widely known). Our low-tech coping strategy as a kid was a box of candles and a torch to find it, when plunged into darkness. Enormous fun although for some reason my parents never seemed to enjoy the power cuts that much. 

 

 

 

 

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34 minutes ago, KevMc said:

This thought has been running through my tiny brain as I have been reading this thread .. why don't home owners also look to battery power as a backup

 

Cost, roughly £1000 per kW for batteries and inverter. 

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21 minutes ago, Mike the Boilerman said:

 

Because until now, there has been no need!

 

As a kid we had regular power cuts (as a lot of people living in countryside locations still do, although this is not widely known). Our low-tech coping strategy as a kid was a box of candles and a torch to find it, when plunged into darkness. Enormous fun although for some reason my parents never seemed to enjoy the power cuts that much. 

 

 

 

 

 

Indeed, up until the privatisation of the then electricity boards, their governing body, the Electricity Council, used to produce annual data on outages, locations and durations.

 

When this stopped, the group I headed up was charged by BT to monitor it for

BT Exchanges. We were only interested in outages of more than an hour because in the event of a generator failing to start the batteries should last that long.

 

Rural outages were ten times more frequent than urban ones because they rely on overhead cables for their mains electricity.

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25 minutes ago, Mike the Boilerman said:

 

Because until now, there has been no need!

 

As a kid we had regular power cuts (as a lot of people living in countryside locations still do, although this is not widely known). Our low-tech coping strategy as a kid was a box of candles and a torch to find it, when plunged into darkness. Enormous fun although for some reason my parents never seemed to enjoy the power cuts that much. 

 

 

 

 

We used to have lots of power cuts but not so many since they rewired the main feed through the village.

 

Still know exactly where the candles and matches are and I can get to them in the dark without a torch as the furniture doesn't move.

 

Sadly the dog does move...........................

 

George

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33 minutes ago, cuthound said:

 

Cost, roughly £1000 per kW for batteries and inverter. 

If it was incorporated along with Solar panels wouldn't the cost be offset by the savings (eventually)

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2 minutes ago, KevMc said:

If it was incorporated along with Solar panels wouldn't the cost be offset by the savings (eventually)

Been looking into this now there is no FIT it will take at least 25years to payback, not sure I will live to 93 ;)

 

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3 minutes ago, KevMc said:

If it was incorporated along with Solar panels wouldn't the cost be offset by the savings (eventually)

 

Probably not because the batteries would need replacing every 7-10 years, and the inverter would periodically fail.

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3 minutes ago, cuthound said:

 

Probably not because the batteries would need replacing every 7-10 years, and the inverter would periodically fail.

I'd expect the tech to improve over time - specially with a much larger market, if we put the effort into it

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26 minutes ago, KevMc said:

I'd expect the tech to improve over time - specially with a much larger market, if we put the effort into it

 

Yes Lithium Ion batteries are available at around 5-10 times the price of LA's and graphene batteries are forecast replace Lithium Ions in phones etc within the next few years. There are also loads of unproven battery technologies emerging as well. However it is in the manufacturers interest to milk high prices for as long as they can. 😣

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On 13/08/2019 at 23:10, peterboat said:

But it works in Australia so why wouldn't they work here? Is it because we would be upside down?

I agree with you and cannot wait until all electricity is produced this way

 Roll on those big wind turbines 

No it works in south australia for a very short time while they get the bass connector sorted out, and then buy power from nsw and victoria.

Then they get everything else going. That includes the snowy mountain scheme where the used stored water runs the turbines ( and is pumped back upon economy 7....)

 

they use the tesla battery in the summer for peak demand. when the renewables  failed they really were in trouble, peak summer no aircon hospitals down.

the tesla battery has only a very short life.

Australia is so far ahead that they shut their main power station down ( hazelwood) and the next summer had an ingenious solution to the predicted outages.

yep 1000 diesel generators in morwell.

on a 42 degree day they fired them up.

the locals used to brown coal dust and smoke didnt know what hit them.

 

the day after they shut hazelwood i cycled past on my way to work, the brown haze had gone, but so had the electricity...

They were load spilling this year as well.

industry stops schools shut...

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