Grid Stability and Renewable Power...

[Jeff Liebermann]

On Tue, 19 Apr 2022 15:53:36 -0000 (UTC), Bertrand Sindri
<bertrand.sindri@yahoo.com> wrote:

Jeff Liebermann <jeffl@cruzio.com> wrote:
The fun begins if the grid frequency slows down a little due to a
decrease in source supply or an increase in load. A short while
later, the generators are adjusted to bring everything back to exactly
50 or 60Hz. However, that\'s not good because the frequency also needs
to be adjusted to compensate for the time lost during the power sag.

Time error correction is no longer done in the US after 2017:

https://www.usatoday.com/story/money/economy/2018/05/17/clocks-may-change-power-grid-maintenance-rule/619864002/

\"... so last year, the correction part was quietly eliminated by the
Federal Energy Regulatory Commission.\"

https://www.balch.com/insights/publications/2017/01/www.balch.com/-/media/erl-blog/fercordersrulesdelegated-order-approving-retirement-for-reliability-standard-bal0040.pdf

Thanks. The above document seems to suggest that it\'s only replacing
one standard (BAL-003-xxx) with a new and improved version
(BAL-004-0). Without reading the standard, I can\'t tell if TEC (time
error correction) is still being performed using a new and improved
TEC procedure or standard. I said \"seems to suggest\" because I\'m
having difficulties decoding the legalese.

Quoting:
NERC explains that since Reliability Standard
BAL-004-0 became effective, improvements have been
made to mandatory Reliability Standards (such as
the development of Reliability Standards BAL-003-1.1
and BAL-001-2 and the Interconnection Reliability
Operations and Coordination (IRO) Standards) that
help ensure continued adherence to frequency
approximating 60 Hertz over long-term averages and
make Reliability Standard BAL-004-0 redundant.

Note that \"continued adherence to frequency...\" indicates that
something is being done to maintain a \"long-term average\" 60Hz. If
synchronous clocks were not an issue, there would be no need for this
\"long-term average\". Also, just because it is no longer a regulatory
requirement to maintain clock sync doesn\'t prevent the utilities from
doing it anyway possibly because no utility wants to be first to be
identified as causing a problem with some forgotten device due to an
oversight. Also note that compliance to this reliability standard is
voluntary, not mandatory:
<https://www.nerc.com/pa/Stand/Pages/SARUrgentActionBAL004.aspx>
\"Time Monitor is a voluntary service and, therefore, should not be
penalized for non compliance.\" Note that this was done in 2008.


--
Jeff Liebermann jeffl@cruzio.com
PO Box 272 http://www.LearnByDestroying.com
Ben Lomond CA 95005-0272
Skype: JeffLiebermann AE6KS 831-336-2558

 

[Phil Allison]

jeff.li...@gmail.com wrote:
==================

** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?

Rotating machines would then follow them.

...... Phil

The fun begins if the grid frequency slows down a little due to a
decrease in source supply or an increase in load. A short while
later, the generators are adjusted to bring everything back to exactly
50 or 60Hz.

** That is not what really happens.

The supply frequency is in constant, slow oscillation around the nominal 50 or 60Hz.
Anyone with a period counter or a scope in X-Y mode can verify this.

Excursions are limited to about +/- 0.1 Hz and take several minutes per cycle.
There are web pages that show this in real time too.

In any case, the millions of mostly electronic clocks that rely on this frequency cannot be trusted due to the high probability of local outages and tripping circuit breakers.


....... Phil

 

[Ricky]

On Tuesday, April 19, 2022 at 6:15:55 PM UTC-4, palli...@gmail.com wrote:

jeff.li...@gmail.com wrote:
==================

** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?

Rotating machines would then follow them.

...... Phil

The fun begins if the grid frequency slows down a little due to a
decrease in source supply or an increase in load. A short while
later, the generators are adjusted to bring everything back to exactly
50 or 60Hz.

** That is not what really happens.

The supply frequency is in constant, slow oscillation around the nominal 50 or 60Hz.
Anyone with a period counter or a scope in X-Y mode can verify this.

Excursions are limited to about +/- 0.1 Hz and take several minutes per cycle.
There are web pages that show this in real time too.

In any case, the millions of mostly electronic clocks that rely on this frequency cannot be trusted due to the high probability of local outages and tripping circuit breakers.

So, mismatches in generation and load do not result in a change in frequency? That\'s an interesting idea. So where does rotational inertia come in?

--

Rick C.

--- Get 1,000 miles of free Supercharging
--- Tesla referral code - https://ts.la/richard11209

 

[Martin Brown]

On 18/04/2022 15:43, Ricky wrote:

On Monday, April 18, 2022 at 5:45:31 AM UTC-4, Martin Brown wrote:

The calculation that wasn\'t allowed for in the UK is that with
domestic generation on home roofs and on a sunny day when you shed
\"load\" you will also shed a whole bunch of local solar PV
generation as well.

Let\'s leave the small, domestic systems out of the conversation.

But they are critical to understanding one of the key modes of failure
that took down so much of the UK grid. Roughly 2% of roofs have solar
panels on each producing 4kW in good sunlight and at a time when average
household load is about 200W so per thousand homes you have:

200kW load and 80kW local solar PV. The system tried to stabilise itself
by shedding 1MW of load but at the same time it lost 400kW of local
generation as well and so had to keep on dropping chunks off supply. It
was always behind the curve at every step of the way. The algorithm
expected to overshoot and then be able to reconnect. It didn\'t happen.

As the number of homes with solar PV increases it becomes harder and
harder to ignore this effect at >5% they become net exporters at least
when the sun is shining.

The particular point someone was making was that no inverters used
with wind power (or solar farms) has the ability to help stabilize
the grid, because there is no rotating inertia. It was not claimed
that this was not possible, but it was implied by pointing out no one
had done this yet and it would be a very useful feature.

There is some rotating inertia in the spinning wind turbine blades but
nothing like as much as there is in a big mechanical steam turbine but
enough to keep going provided that you allow the frequency to drift.

Seems to me it would require some way of increasing the power output,
which means the facility has to run below optimal efficiency to have
anything in reserve.

One way to build some resilience is to have local battery storage that
is immediately available to boost output when there is a sudden change
in load. US & Australia has a fair sized one to control peak loading.

https://www.bbc.com/future/article/20201217-renewable-power-the-worlds-largest-battery

UK has one but it is a complete toy and wasn\'t in the right place to do
any good last time. UK has a structural problem in that most power is
generated in the north and shipped down to the south to be used. The
upshot of this if they lose either of the big N-S EHT supergrid lines
then the south is very short of electricity and something has to give.

Pumped storage reservoirs are our most effective load balancing tool for
immediate generation of more power. Routine balancing is done by
adjusting power delivered the ultimate sink loads (on very favourable
intermittent tariffs). Unfortunately if you have already asked them to
power down you don\'t have that option (as has occurred some winters).

The advantage of natural inertia, is the continuous nature. As much
energy as is needed is available if you are able to tolerate the
reduction in frequency. Of course, there is a limit to the inertia
available, but it seems to do the job pretty well in most cases,
while currently we seem to get nothing from solar and wind power
facilities.

You can still simulate inertia by allowing the inverter to drift further
off frequency than the standard rules would normally allow. Something
like this tweak has been done to avoid quite so much chaos next time.

I presume that they have fixed the assumptions that caused the load
shedding algorithms to misjudge how much *absolute* load they would
have to drop to obtain a net saving of 1MW in future. It was a pretty
catastrophic mode of cascade systems failure for what should have been a
routine lightning strike with local cutout protection and recovery.

I don\'t think it would be such a problem in the USA since peak solar PV
output and peak domestic aircon requirements more or less balance it
out. In the UK there is hardly any domestic aircon so that in sunny
weather most of what is generated by domestic PV is exported to the grid
(especially in the late afternoon).

A stupid feature of the UK\'s \"green\" feed in tariff makes it cost
effective to have solar PV power and turn it into domestic hot water!
After market gizmos abound to do this automatically. You are deemed to
export half of what you generate irrespective of using it or not.

--
Regards,
Martin Brown

 

[Martin Brown]

On 19/04/2022 23:53, Ricky wrote:

On Tuesday, April 19, 2022 at 6:15:55 PM UTC-4, palli...@gmail.com wrote:
jeff.li...@gmail.com wrote:
==================

** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?

Rotating machines would then follow them.

...... Phil

The fun begins if the grid frequency slows down a little due to a
decrease in source supply or an increase in load. A short while
later, the generators are adjusted to bring everything back to exactly
50 or 60Hz.

** That is not what really happens.

The supply frequency is in constant, slow oscillation around the nominal 50 or 60Hz.
Anyone with a period counter or a scope in X-Y mode can verify this.

Excursions are limited to about +/- 0.1 Hz and take several minutes per cycle.
There are web pages that show this in real time too.

In general it often tends to run consistently slow when the loads are at
highest peak (like evening meal time in the UK) or peak afternoon aircon
load in the USA and consistently fast in the middle of the night.

The latter used to be a nuisance for some old school telescope drives
that were mains synchronous motor based. When you are tracking to arc
second precision the mains just isn\'t accurate enough. They moved to
quartz crystal references or servo with autoguider pretty much as soon
as the technology became available. Much less work for the observer.

>> In any case, the millions of mostly electronic clocks that rely on this frequency cannot be trusted due to the high probability of local outages and tripping circuit breakers.

Quite a lot of traffic lights still rely on it too.

The advent of cheap VLF time modules has made it much less of a problem.
Mains powered synchronous motor based kit has all but died out now. But
there are plenty of legacy traffic lights that need resetting after a
long powercut (since they tend to resume from whatever time they were at
when the power goes down). A few minutes is fairly harmless but a few
hours and the rush hour traffic flows end up in total chaos.

So, mismatches in generation and load do not result in a change in frequency? That\'s an interesting idea. So where does rotational inertia come in?

That isn\'t what he said.

They have always allowed the mains frequency to drift slightly with time
to accommodate minor imbalances in the load at peak times. Heavy load
means lower frequency and lighter loads the allow it to run a bit fast.
It hunts slowly around the nominal frequency since if they predict that
load will increase they will bring more generation onstream.

To keep dead reckoning mains powered clocks based on synchronous motors
accurate they increase the frequency slightly when the loads are lowest
in the middle of the night. The average mains frequency over 24 hours
is held to very high precision linked back to atomic time standards.
(from what others have said it seems the USA have relaxed this rule)

Network phase in the UK is relatively well defined since 800km << 6000km
(one wavelength at 50Hz).

But in the USA where network distances are much greater the network
phase must be locally determined. eg. SF to NY is ~4000km which is a
very non-negligible fraction of a 60hz wavelength of 5000km.

--
Regards,
Martin Brown

 

[Phil Allison]

Martin Bullshit LIAR Brown wrote:

=============================

** What happens now is that inverters feeding the grid *track* the existing frequency - cos they are minor players in supplying the load.
But what if that were not the case, they became the majority suppliers and and instead were locked to a central clock ?

Rotating machines would then follow them.

...... Phil

The fun begins if the grid frequency slows down a little due to a
decrease in source supply or an increase in load. A short while
later, the generators are adjusted to bring everything back to exactly
50 or 60Hz.

** That is not what really happens.

The supply frequency is in constant, slow oscillation around the nominal 50 or 60Hz.
Anyone with a period counter or a scope in X-Y mode can verify this.

Excursions are limited to about +/- 0.1 Hz and take several minutes per cycle.
There are web pages that show this in real time too.

In general it often tends to run consistently slow when the loads are at
highest peak (like evening meal time in the UK) or peak afternoon aircon
load in the USA and consistently fast in the middle of the night.

** So you have never checked the *actual frequency* or followed on-line pages that give a 24/7 readout.
Your whole bullshit is just fucking made up.

LIKE EVERY POST YOU HAVE EVER MADE !!
-----------------------------------------------------------------------------

In any case, the millions of mostly electronic clocks that rely on this frequency
cannot be trusted due to the high probability of local outages and tripping circuit breakers.

Quite a lot of traffic lights still rely on it too.

** FFS what a fucking ridiculous red herring !!!

So, mismatches in generation and load do not result in a change in frequency?
That\'s an interesting idea. So where does rotational inertia come in?

That isn\'t what he said.

** At least you got that one right.

Ricky is a total fucking, bullshitting ASD fucked IDIOT .
So are YOU !!!

They have always allowed the mains frequency to drift slightly with time
to accommodate minor imbalances in the load at peak times.

** Bullshit.

> Heavy load means lower frequency

** Bullshit.

> and lighter loads the allow it to run a bit fast.

** Bullshit.

It hunts slowly around the nominal frequency since if they predict that
load will increase they will bring more generation onstream.

** Bullshit.

To keep dead reckoning mains powered clocks based on synchronous motors
accurate they increase the frequency slightly when the loads are lowest
in the middle of the night.

** Bullshit.


...... Phil

 

[Don Y]

On 4/20/2022 1:53 AM, Martin Brown wrote:

They have always allowed the mains frequency to drift slightly with time to
accommodate minor imbalances in the load at peak times. Heavy load means lower
frequency and lighter loads the allow it to run a bit fast. It hunts slowly
around the nominal frequency since if they predict that load will increase they
will bring more generation onstream.

To keep dead reckoning mains powered clocks based on synchronous motors
accurate they increase the frequency slightly when the loads are lowest in the
middle of the night. The average mains frequency over 24 hours is held to very
high precision linked back to atomic time standards.

In the early-mid 70\'s, I wanted a clock that wouldn\'t have to deal with
the silly time changes so designed one around a 10MHz TCXO that we happened
to use in one of our products. I was chagrined to discover it was off several
seconds each month -- until I looked at the tolerance on the oscillator
(a few PPM).

As I couldn\'t step *up* to an OCXO (too much power required to keep it
operating through power outages), I looked to the mains as an alternate time
source (\"how can *regular* clocks keep such good time?\"). Eventually,
replacing all of the discrete logic with a processor I could \"watch\" the
mains frequency vary (against the stable TCXO) over the course of a day.
I.e., the mains-derived time had short-term stability problems but
long-term accuracy.

So, I fell upon the idea of using the mains frequency to tweek the TCXO\'s
notion of time. Then, realized the TCXO was essentially unnecessary;
any time source of sufficient short term stability could suffice -- if I
could *measure* that frequency against the mains over VERY long intervals.

Subsequent clocks have been built around cheap watch crystals/RTCs and
keep remarkably good time (much better than an undisciplined PC). I now
discipline my NTP server with such a source (I don\'t care if my PCs are
\"off\" by N seconds -- as long as they are ALWAYS off by N seconds -- as
this lets me operate without a GPS signal *or* routing them!)

> (from what others have said it seems the USA have relaxed this rule)

I\'d been told that was *supposed* to happen. But, haven\'t seen any practical
consequences on any of my mains-disciplined clocks.

Network phase in the UK is relatively well defined since 800km << 6000km (one
wavelength at 50Hz).

But in the USA where network distances are much greater the network phase must
be locally determined. eg. SF to NY is ~4000km which is a very non-negligible
fraction of a 60hz wavelength of 5000km.

There is a group that (informally?) monitors this nationwide, here (US):
<https://en.wikipedia.org/wiki/FNET>
I question how reliable their phase measurements are, given that they are
looking at \"consumer\" distributions and not the \"backbone\" of the
power network. (but, *frequency* observations should be dead to nuts)

 

[whit3rd]

On Wednesday, April 20, 2022 at 2:44:26 AM UTC-7, palli...@gmail.com wrote:

Martin Brown wrote:

They have always allowed the mains frequency to drift slightly with time
to accommodate minor imbalances in the load at peak times.
** Bullshit.

Maybe; the \'drift slightly with time\' sounds vague.

Heavy load means lower frequency
** Bullshit.

Not so. Rotating machinery generates that frequency, and heavy load
on the generators does slow their rotation; regardless of control settings,
the feedback gain cannot be infinite (that causes more problems than it solves).

 

[Jeroen Belleman]

On 2022-04-20 19:59, whit3rd wrote:

On Wednesday, April 20, 2022 at 2:44:26 AM UTC-7, palli...@gmail.com wrote:
Martin Brown wrote:

They have always allowed the mains frequency to drift slightly with time
to accommodate minor imbalances in the load at peak times.
** Bullshit.

Maybe; the \'drift slightly with time\' sounds vague.

Heavy load means lower frequency
** Bullshit.

Not so. Rotating machinery generates that frequency, and heavy load
on the generators does slow their rotation; regardless of control settings,
the feedback gain cannot be infinite (that causes more problems than it solves).

On the European mains network, the proportionality constant is
about 20GW/Hz. All sufficiently large generating facilities are
supposed to adjust their power output to drive the long-term
average frequency to its nominal value. A Swiss source provides
the reference frequency.

Jeroen Belleman

 

[Ricky]

On Wednesday, April 20, 2022 at 4:49:38 AM UTC-4, Martin Brown wrote:

On 18/04/2022 15:43, Ricky wrote:
On Monday, April 18, 2022 at 5:45:31 AM UTC-4, Martin Brown wrote:

The calculation that wasn\'t allowed for in the UK is that with
domestic generation on home roofs and on a sunny day when you shed
\"load\" you will also shed a whole bunch of local solar PV
generation as well.

Let\'s leave the small, domestic systems out of the conversation.
But they are critical to understanding one of the key modes of failure
that took down so much of the UK grid. Roughly 2% of roofs have solar
panels on each producing 4kW in good sunlight and at a time when average
household load is about 200W so per thousand homes you have:

200kW load and 80kW local solar PV. The system tried to stabilise itself
by shedding 1MW of load but at the same time it lost 400kW of local
generation as well and so had to keep on dropping chunks off supply. It
was always behind the curve at every step of the way. The algorithm
expected to overshoot and then be able to reconnect. It didn\'t happen.

As the number of homes with solar PV increases it becomes harder and
harder to ignore this effect at >5% they become net exporters at least
when the sun is shining.

I don\'t care about the issues in the UK. You and others have stated many times that the UK grid is bollixed up beyond all redemption. So not much to learn from it for a real grid.

The particular point someone was making was that no inverters used
with wind power (or solar farms) has the ability to help stabilize
the grid, because there is no rotating inertia. It was not claimed
that this was not possible, but it was implied by pointing out no one
had done this yet and it would be a very useful feature.
There is some rotating inertia in the spinning wind turbine blades but
nothing like as much as there is in a big mechanical steam turbine but
enough to keep going provided that you allow the frequency to drift.
Seems to me it would require some way of increasing the power output,
which means the facility has to run below optimal efficiency to have
anything in reserve.
One way to build some resilience is to have local battery storage that
is immediately available to boost output when there is a sudden change
in load. US & Australia has a fair sized one to control peak loading.

https://www.bbc.com/future/article/20201217-renewable-power-the-worlds-largest-battery

UK has one but it is a complete toy and wasn\'t in the right place to do
any good last time. UK has a structural problem in that most power is
generated in the north and shipped down to the south to be used. The
upshot of this if they lose either of the big N-S EHT supergrid lines
then the south is very short of electricity and something has to give.

Pumped storage reservoirs are our most effective load balancing tool for
immediate generation of more power. Routine balancing is done by
adjusting power delivered the ultimate sink loads (on very favourable
intermittent tariffs). Unfortunately if you have already asked them to
power down you don\'t have that option (as has occurred some winters).

Yes, yes, yes, but not what we are discussing.

The advantage of natural inertia, is the continuous nature. As much
energy as is needed is available if you are able to tolerate the
reduction in frequency. Of course, there is a limit to the inertia
available, but it seems to do the job pretty well in most cases,
while currently we seem to get nothing from solar and wind power
facilities.
You can still simulate inertia by allowing the inverter to drift further
off frequency than the standard rules would normally allow. Something
like this tweak has been done to avoid quite so much chaos next time.

I presume that they have fixed the assumptions that caused the load
shedding algorithms to misjudge how much *absolute* load they would
have to drop to obtain a net saving of 1MW in future. It was a pretty
catastrophic mode of cascade systems failure for what should have been a
routine lightning strike with local cutout protection and recovery.

I don\'t think it would be such a problem in the USA since peak solar PV
output and peak domestic aircon requirements more or less balance it
out. In the UK there is hardly any domestic aircon so that in sunny
weather most of what is generated by domestic PV is exported to the grid
(especially in the late afternoon).

A stupid feature of the UK\'s \"green\" feed in tariff makes it cost
effective to have solar PV power and turn it into domestic hot water!
After market gizmos abound to do this automatically. You are deemed to
export half of what you generate irrespective of using it or not.

Yes, you keep telling us how bad the UK grid is. I agree.

--

Rick C.

--+ Get 1,000 miles of free Supercharging
--+ Tesla referral code - https://ts.la/richard11209

 

[Ricky]

On Wednesday, April 20, 2022 at 1:59:24 PM UTC-4, whit3rd wrote:

On Wednesday, April 20, 2022 at 2:44:26 AM UTC-7, palli...@gmail.com wrote:
Martin Brown wrote:

They have always allowed the mains frequency to drift slightly with time
to accommodate minor imbalances in the load at peak times.
** Bullshit.
Maybe; the \'drift slightly with time\' sounds vague.
Heavy load means lower frequency
** Bullshit.
Not so. Rotating machinery generates that frequency, and heavy load
on the generators does slow their rotation; regardless of control settings,
the feedback gain cannot be infinite (that causes more problems than it solves).

No, that\'s not quite right. It is the balance between load and supply that causes the frequency drift. Too much energy feeding into the generators and the frequency increases as the excess is absorbed by the rotational inertia. Too little energy feeding into the generators and the frequency decreases as the inertia is drawn down to supply the excess load. The difference in source and load match determines the derivative of the frequency.

--

Rick C.

-+- Get 1,000 miles of free Supercharging
-+- Tesla referral code - https://ts.la/richard11209

 

[Glen Walpert]

On Wed, 20 Apr 2022 10:59:20 -0700 (PDT), whit3rd wrote:

On Wednesday, April 20, 2022 at 2:44:26 AM UTC-7, palli...@gmail.com
wrote:
Martin Brown wrote:

They have always allowed the mains frequency to drift slightly with
time to accommodate minor imbalances in the load at peak times.
** Bullshit.

Maybe; the \'drift slightly with time\' sounds vague.

Heavy load means lower frequency
** Bullshit.

Not so. Rotating machinery generates that frequency, and heavy load on
the generators does slow their rotation; regardless of control settings,
the feedback gain cannot be infinite (that causes more problems than it
solves).

Right. In single generator operation the governor will be set to
constant frequency mode, and will hold a constant frequency at all
loads. But in order to parallel generators and share the load in a
stable manner the governors must be placed in droop mode, where a
percentage of power level is subtracted from the governors set point.
When paralleled with a much larger bus, the governor cannot regulate
generator speed, that is locked to the grid, it regulates real power
output instead. Connect initially with no load and slightly higher speed
at matched phase and the generator picks up a minute load, then if droop
is set at 5% for instance cranking up the governor speed knob 5% will
give you full load. So all rotating generators on the grid provide more
power as frequency drops and less as it rises, more power delivered tends
to up frequency, less reduces. Power delivery is set by the central grid
operator for all large generating stations in order to match the load and
thus keep frequency ~constant.

There is a similar situation with voltage regulation, in single generator
operation the field exciter regulates voltage. When paralleled with an
\"infinite bus\" the exciter can no longer regulate voltage, it
automatically (via aux contacts on the paralleling breaker) goes into
reactive power regulating mode, initially set at zero reactive power if
voltages were matched when paralleling and left there unless the utility
pays for reactive power. Multiple generators at the same location are
cross compensated to share reactive power, and reactive power on the grid
is balanced by the grid operator. There are some interesting stability
issues with reactive power since it has twice the effect on rotating
generator voltage as real power, but this is well understood if not easy
to remedy - as static synchronous generators increase in % total grid
power and need to contribute reactive power it will be necessary to turn
some control of them over to the grid operator, as is already being done
in some places, and as was done long ago to stop power sloshing between
rotating generator power plants on the same grid.

(Grid goes undervoltage, SSG\'s up reactive power, grid voltage goes up,
SSG\'s drop reactive power, grid goes undervoltage, etc. Better control
strategy will stop this.)

 

[Ricky]

On Wednesday, April 20, 2022 at 6:21:31 PM UTC-4, Glen Walpert wrote:

On Wed, 20 Apr 2022 10:59:20 -0700 (PDT), whit3rd wrote:

On Wednesday, April 20, 2022 at 2:44:26 AM UTC-7, palli...@gmail.com
wrote:
Martin Brown wrote:

They have always allowed the mains frequency to drift slightly with
time to accommodate minor imbalances in the load at peak times.
** Bullshit.

Maybe; the \'drift slightly with time\' sounds vague.

Heavy load means lower frequency
** Bullshit.

Not so. Rotating machinery generates that frequency, and heavy load on
the generators does slow their rotation; regardless of control settings,
the feedback gain cannot be infinite (that causes more problems than it
solves).
Right. In single generator operation the governor will be set to
constant frequency mode, and will hold a constant frequency at all
loads. But in order to parallel generators and share the load in a
stable manner the governors must be placed in droop mode, where a
percentage of power level is subtracted from the governors set point.
When paralleled with a much larger bus, the governor cannot regulate
generator speed, that is locked to the grid, it regulates real power
output instead. Connect initially with no load and slightly higher speed
at matched phase and the generator picks up a minute load, then if droop
is set at 5% for instance cranking up the governor speed knob 5% will
give you full load. So all rotating generators on the grid provide more
power as frequency drops and less as it rises, more power delivered tends
to up frequency, less reduces. Power delivery is set by the central grid
operator for all large generating stations in order to match the load and
thus keep frequency ~constant.

The part I\'m not clear on is how this is combined with the financial side of things. There are various load accounts and what you describe is generation essentially in bulk. No generator is outputing a specific amount as contracted for by customers. So how does the billing work? If user A, B and C have contracted with supplier K, but supplier K is having to output power according to central control, who is paying supplier K for all the MWh being pumped out if it doesn\'t match what his customers A, B and C are asking for?

--

Rick C.

-++ Get 1,000 miles of free Supercharging
-++ Tesla referral code - https://ts.la/richard11209 0

 

[Anthony William Sloman]

On Thursday, April 21, 2022 at 8:37:33 AM UTC+10, Ricky wrote:

On Wednesday, April 20, 2022 at 6:21:31 PM UTC-4, Glen Walpert wrote:
On Wed, 20 Apr 2022 10:59:20 -0700 (PDT), whit3rd wrote:
On Wednesday, April 20, 2022 at 2:44:26 AM UTC-7, palli...@gmail.com wrote:
Martin Brown wrote:

<snip>

> The part I\'m not clear on is how this is combined with the financial side of things. There are various load accounts and what you describe is generation essentially in bulk. No generator is outputing a specific amount as contracted for by customers. So how does the billing work? If user A, B and C have contracted with supplier K, but supplier K is having to output power according to central control, who is paying supplier K for all the MWh being pumped out if it doesn\'t match what his customers A, B and C are asking for?

In Australia there was an auction every half hour - it\'s now every ten minutes - where the generating companies would offer power to the distribution company which would buy up as much as was needed to satisfy demand, and reject the rest.

The people who retailed the power to their customers at a fixed price per kilowatt hour had to pay for what they took out over that period at the auction price. The price fluctuates a lot.

https://aemo.com.au/en/energy-systems/electricity/national-electricity-market-nem/market-operations/settlements-and-payments/settlements/settlements-residue-auction/guide-to-settlements-residue-auction

https://www.aer.gov.au/wholesale-markets/wholesale-statistics?f%5B0%5D=field_accc_aer_sector%3A4

It all seems to work. Fast start gas-turbine-driven generation only gets turned when the price is likely to be high. Grid-scale batteries and pumped storage can offer power immediately, when the price is high enough. About half the Tesla battery in South Australia is used to buy up power when it is cheap and sell it back when it isn\'t. It makes enough out of it to pay for itself over a decade.

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Bill Sloman, Sydney