Re: [time-nuts] Line Frequeny Stablity

[Andy]

Several years ago (c. 1980) I remember an occasion when the local utility
slipped about 20-25 minutes of effective 'time' over the course of one
night.

I didn't know much about power grids then, except that they existed, and
contributed to certain power blackouts.  But what happened was that the
local utility had gotten disconnected from the rest of the northeast USA
grid, and free-ran overnight at a significantly offset frequency.  I think
it would have been running at around 57 Hz or lower.

Andy
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Re: [time-nuts] Line Frequeny Stablity

[Peter Reilley]

Another purpose of the reheat process is to control moisture.   The term 
"moisture" here
describes the amount of liquid water in the steam as it flows through 
the system.   The spec

for this is generally about .25% moisture.

The temperature of the steam exiting the boiler is very close to the 
boiling point of water
at that pressure.   The energy to boil water is 970 BTU per lb. The 
energy to change
the temperature of water by 1 degree F is 1 BTU per lb.   Thus there is 
very little to be
gained by heating the steam hotter than it's boiling point.   You can't 
add that much
additional energy and have a temperature that you can handle.   Of 
course the boiling point

of water is quite high at these pressures.

The steam enters the turbine at very high temperature and pressure.   As 
it passes
through the many stages of the turbine you would like the pressure and 
temperature
of the steam to remain just above the boiling point.   You want to 
maintain that

balance of pressure and temperature to insure less than .25% moisture.

The reason that the steam must remain "just above" the boiling point is 
any condensation
produces liquid water.This liquid water is very destructive to the 
turbine blades.
The velocity of the steam in the turbine approaches supersonic speeds 
and any little
drops of water hitting the blades at those speeds erodes the steel.   
The areas of the
blades most at risk for this have a very hard material braised onto 
their surface.

But even this gets eroded.   I remember it being called "Stellite".

Reheat is used to raise the temperature of the steam to keep it above the
boiling point at certain stages in it's flow through the turbine.

There is a limit to how hot you can go.   Water has a critical point at 
705 degrees F
at 3200 PSI.Above this point there is no longer a sharp distinction 
between vapor
and water.   There have been super-critical power plants built. But when 
I was in
the business, in the 1970's, they were experimental and not reliable.   
I don't know

if that is true now.

Pete.

On 4/5/2017 5:44 PM, Bryan _ wrote:

There is a pretty nice "How it Works" video on steam turbines. As Pete mentions 
they use valving to control the speed of the turbines, interesting how they reheat the 
steam for the high/medium/low stages.


https://youtu.be/SPg7hOxFItI


-=Bryan=-



From: time-nuts  on behalf of Peter Reilley 

Sent: April 5, 2017 9:34 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Line Frequeny Stablity

The response time in a large plant is very slow.   Large steam plants
running at steady
state are running with their steam valves wide open.   A partially
closed valve is an energy
loss and is only used when changes occur.

The power control for a plant running at a steady load is the amount of
fuel thrown into
the boiler.   When you want more power you shoot more gas, oil, or coal
into the boiler.
For a nuke you pull the control rods.   Behind all of this is a lot of
thermal mass.   Things
don't change quickly.

Pete.

On 4/5/2017 9:01 AM, jimlux wrote:

On 4/4/17 2:28 PM, Thomas D. Erb wrote:

Thanks for the info.


So that tells me how data is recorded - but not how the frequency is
kept stable ?

Is the line frequency now directly tied to GPS clock - with no drift ?

The line frequency is adjusted, for the most part, by adjusting the
prime power (steam valves, dam penstocks, etc.) on the generators at
power stations. That changes the speed, slightly, although as
generator 1 of N starts to get ahead, the electrical load increases,
and it slows down.

It's actually a pretty complex system, since there are a whole raft of
"spring constants" in between the multiple generators in a system,
there's phase shifts due to transmission line inductance and capacitance.

"Stabilizing" a system in the face of changing demand is a non-trivial
task.






Thomas D. Erb
t...@electrictime.com<mailto:t...@electrictime.com> /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com<http://www.electrictime.com<http://www.electrictime.com<http://www.electrictime.com>>
[Facebook]<https://www.facebook.com/pages/Electric-Time-Company-Inc/127918073950854?ref=hl>[Twitter]<https://twitter.com/tower_clocks>[pinterest]<https://www.pinterest.com/electrictime/>

[htmlsig.com]<http://www.electrictime.com/>
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Re: [time-nuts] Line Frequeny Stablity

[Bill Hawkins]

Perhaps I should have clarified that while the synchronous machines all
run at the same frequency, that frequency depends on the balance of
steam (or hydraulic) power to the turbines that spin the generators and
the aggregate power demand. When the power is not balanced, the
frequency of the coupled system will change, but very slowly in
proportion to the size of the network of generators.

I don't know the effects of the DC tieline inverter, which can run at
any set frequency, but any difference in frequency has to affect the
power out of or into the tie line.

As to doing the clock adjustment around quitting time at 5 PM, my
experience is different. A system that took a frequency input and showed
it as a function of time revealed that the frequency sagged during the
workday and the air conditioning day, but was increased to make up the
lost cycles during the minimum load time around 4:30 AM.

In 1955 or so, The Air Force determined that the time of minimum human
activity (and hence the maximum probability of attack) was at 4:30 in
the morning. Independent research with traffic counters revealed a sharp
dip in traffic at that time of day. Adjusting the cycle count at the
time of minimum activity also minimized the cost of making that
adjustment. Sorry, I have no recent data, but it sure feels lonely to be
up at 4:30 AM.

Bill Hawkins


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Jeremy
Nichols
Sent: Wednesday, April 05, 2017 6:57 PM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Line Frequeny Stablity

A fun way to monitor the state of the grid is to watch the web site of
the Power Information Technology Laboratory <http://powerit.utk.edu> at
the University of Tennessee <http://www.utk.edu>, Their site lists in
both tabular and graphical (map) form the frequency of the grid. Most of
it is USA-based but there are a few other countries also monitored.

I have one of the monitors (in the table display page <
http://fnetpublic.utk.edu/tabledisplay.html> my monitor is #853 in the
Western Interconnection-I'm in California).

The monitors, about the size of a thick hardback book, plug into a
convenient AC line outlet, connect to your Internet router, and have a
small puck-style GPS antenna so that it knows the time and where it is.
The unit has an LCD display of date, time, line voltage, and line
frequency.
The voltage is shown to 3 decimal digits of resolution and the frequency
to four digits.

I got my monitor from the U of T after I sent them a report on my
home-made monitor's results. It's interesting to watch the frequency
wander up and down but always average very close to 60.000 Hz. They saw
I had an interest and offered me one of their toys. The only thing it
doesn't do is connect to my PC so I can monitor it long-term. I suppose
if I were clever with network stuff there'd be a way to tap into its
data stream.

Jeremy, N6WFO


On Wed, Apr 5, 2017 at 2:12 PM, Bob kb8tq  wrote:

> Hi
>
> Back in high school, one of the radio club members figured out that 
> the "clock adjustment" took place locally between 4:30 and 5:00 PM. 
> Needless to say, pretty much everybody spent the next week listening 
> to WWV and watching the clock's second hand go out of sync with the
beeps.
> This was back in the  late 1960's
> and the idea of a grid was a bit looser than it is today. Indeed it 
> was post 1964 so there *were* grids big enough to take out the whole 
> north east section of the US. Since we were very much in that area the

> topic of grid sync came up. Nobody ever really had a good answer to 
> that question. That included the guys who ran the local power company.
>
> Bob
>
> > On Apr 5, 2017, at 3:05 PM, Hal Murray 
wrote:
> >
> >
> > preilley_...@comcast.net said:
> >> When I installed power plants in the 1970's they has a special
"clock"
> that
> >> showed the cumulative error in terms of clock time.
> >
> > How big were the grids back then?
> >
> > What was the typical range of error over a day or month?
> >
> >
> >> If the generator ran a little too fast the clock would move
forward.
> As
> >> the operator observed the clock moving away from zero he would 
> >> reduce
> the
> >> plant's  power and the clock would move backward toward zero.  ...
> >
> > Does that operator control a single generator or a whole grid?
> >
> > Does having a human in the loop help the control loop stability?
> >
> >
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com To

Re: [time-nuts] Line Frequeny Stablity

[Bryan _]

There is a pretty nice "How it Works" video on steam turbines. As Pete mentions 
they use valving to control the speed of the turbines, interesting how they 
reheat the steam for the high/medium/low stages.


https://youtu.be/SPg7hOxFItI


-=Bryan=-



From: time-nuts  on behalf of Peter Reilley 

Sent: April 5, 2017 9:34 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Line Frequeny Stablity

The response time in a large plant is very slow.   Large steam plants
running at steady
state are running with their steam valves wide open.   A partially
closed valve is an energy
loss and is only used when changes occur.

The power control for a plant running at a steady load is the amount of
fuel thrown into
the boiler.   When you want more power you shoot more gas, oil, or coal
into the boiler.
For a nuke you pull the control rods.   Behind all of this is a lot of
thermal mass.   Things
don't change quickly.

Pete.

On 4/5/2017 9:01 AM, jimlux wrote:
> On 4/4/17 2:28 PM, Thomas D. Erb wrote:
>> Thanks for the info.
>>
>>
>> So that tells me how data is recorded - but not how the frequency is
>> kept stable ?
>>
>> Is the line frequency now directly tied to GPS clock - with no drift ?
>
> The line frequency is adjusted, for the most part, by adjusting the
> prime power (steam valves, dam penstocks, etc.) on the generators at
> power stations. That changes the speed, slightly, although as
> generator 1 of N starts to get ahead, the electrical load increases,
> and it slows down.
>
> It's actually a pretty complex system, since there are a whole raft of
> "spring constants" in between the multiple generators in a system,
> there's phase shifts due to transmission line inductance and capacitance.
>
> "Stabilizing" a system in the face of changing demand is a non-trivial
> task.
>
>
>
>
>
>>
>> Thomas D. Erb
>> t...@electrictime.com<mailto:t...@electrictime.com> /
>> Electric Time Company, Inc.
>> Office: 508-359-4396 x 117 / Fax: 508-359-4482
>> 97 West Street Medfield, MA 02052 USA
>> www.electrictime.com<http://www.electrictime.com<http://www.electrictime.com<http://www.electrictime.com>>
>> [Facebook]<https://www.facebook.com/pages/Electric-Time-Company-Inc/127918073950854?ref=hl>[Twitter]<https://twitter.com/tower_clocks>[pinterest]<https://www.pinterest.com/electrictime/>
>>
>> [htmlsig.com]<http://www.electrictime.com/>
>> ___
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>> https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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>>
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Re: [time-nuts] Line Frequeny Stablity

[Bob kb8tq]

Hi

Well ok, the rest of the story ….

The process of watching the line voltage slip lead me to buy my first 
“frequency counter”. 
It was a 1950’s vintage tube based Beckman “EPUT Meter”. I doubt it cost me 
over $40 at 
the time. It was well used but still functional   It clocked away on a  massive 
 MHz time base 
(that’s singular not plural) and turned out to be plenty good enough to show 
jitter
on a 60 Hz sine wave. That got me into questions about why and stability and …. 
here I am
decades later.

Bob

> On Apr 5, 2017, at 7:57 PM, Jeremy Nichols  wrote:
> 
> A fun way to monitor the state of the grid is to watch the web site of
> the Power
> Information Technology Laboratory  at the University
> of Tennessee , Their site lists in both tabular and
> graphical (map) form the frequency of the grid. Most of it is USA-based but
> there are a few other countries also monitored.
> 
> I have one of the monitors (in the table display page <
> http://fnetpublic.utk.edu/tabledisplay.html> my monitor is #853 in the
> Western Interconnection—I'm in California).
> 
> The monitors, about the size of a thick hardback book, plug into a
> convenient AC line outlet, connect to your Internet router, and have a
> small puck-style GPS antenna so that it knows the time and where it is. The
> unit has an LCD display of date, time, line voltage, and line frequency.
> The voltage is shown to 3 decimal digits of resolution and the frequency to
> four digits.
> 
> I got my monitor from the U of T after I sent them a report on my home-made
> monitor's results. It's interesting to watch the frequency wander up and
> down but always average very close to 60.000 Hz. They saw I had an interest
> and offered me one of their toys. The only thing it doesn't do is connect
> to my PC so I can monitor it long-term. I suppose if I were clever with
> network stuff there'd be a way to tap into its data stream.
> 
> Jeremy, N6WFO
> 
> 
> On Wed, Apr 5, 2017 at 2:12 PM, Bob kb8tq  wrote:
> 
>> Hi
>> 
>> Back in high school, one of the radio club members figured out that the
>> “clock adjustment” took place
>> locally between 4:30 and 5:00 PM. Needless to say, pretty much everybody
>> spent the next week listening
>> to WWV and watching the clock’s second hand go out of sync with the beeps.
>> This was back in the  late 1960’s
>> and the idea of a grid was a bit looser than it is today. Indeed it was
>> post 1964 so there *were* grids big
>> enough to take out the whole north east section of the US. Since we were
>> very much in that area the
>> topic of grid sync came up. Nobody ever really had a good answer to that
>> question. That included the
>> guys who ran the local power company.
>> 
>> Bob
>> 
>>> On Apr 5, 2017, at 3:05 PM, Hal Murray  wrote:
>>> 
>>> 
>>> preilley_...@comcast.net said:
 When I installed power plants in the 1970's they has a special "clock"
>> that
 showed the cumulative error in terms of clock time.
>>> 
>>> How big were the grids back then?
>>> 
>>> What was the typical range of error over a day or month?
>>> 
>>> 
 If the generator ran a little too fast the clock would move forward.
>> As
 the operator observed the clock moving away from zero he would reduce
>> the
 plant's  power and the clock would move backward toward zero.  ...
>>> 
>>> Does that operator control a single generator or a whole grid?
>>> 
>>> Does having a human in the loop help the control loop stability?
>>> 
>>> 
>>> 
>>> --
>>> These are my opinions.  I hate spam.
>>> 
>>> 
>>> 
>>> ___
>>> time-nuts mailing list -- time-nuts@febo.com
>>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>>> and follow the instructions there.
>> 
>> ___
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>> To unsubscribe, go to https://www.febo.com/cgi-bin/
>> mailman/listinfo/time-nuts
>> and follow the instructions there.
>> 
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Re: [time-nuts] Line Frequeny Stablity

[Jeremy Nichols]

A fun way to monitor the state of the grid is to watch the web site of
the Power
Information Technology Laboratory  at the University
of Tennessee , Their site lists in both tabular and
graphical (map) form the frequency of the grid. Most of it is USA-based but
there are a few other countries also monitored.

I have one of the monitors (in the table display page <
http://fnetpublic.utk.edu/tabledisplay.html> my monitor is #853 in the
Western Interconnection—I'm in California).

The monitors, about the size of a thick hardback book, plug into a
convenient AC line outlet, connect to your Internet router, and have a
small puck-style GPS antenna so that it knows the time and where it is. The
unit has an LCD display of date, time, line voltage, and line frequency.
The voltage is shown to 3 decimal digits of resolution and the frequency to
four digits.

I got my monitor from the U of T after I sent them a report on my home-made
monitor's results. It's interesting to watch the frequency wander up and
down but always average very close to 60.000 Hz. They saw I had an interest
and offered me one of their toys. The only thing it doesn't do is connect
to my PC so I can monitor it long-term. I suppose if I were clever with
network stuff there'd be a way to tap into its data stream.

Jeremy, N6WFO


On Wed, Apr 5, 2017 at 2:12 PM, Bob kb8tq  wrote:

> Hi
>
> Back in high school, one of the radio club members figured out that the
> “clock adjustment” took place
> locally between 4:30 and 5:00 PM. Needless to say, pretty much everybody
> spent the next week listening
> to WWV and watching the clock’s second hand go out of sync with the beeps.
> This was back in the  late 1960’s
> and the idea of a grid was a bit looser than it is today. Indeed it was
> post 1964 so there *were* grids big
> enough to take out the whole north east section of the US. Since we were
> very much in that area the
> topic of grid sync came up. Nobody ever really had a good answer to that
> question. That included the
> guys who ran the local power company.
>
> Bob
>
> > On Apr 5, 2017, at 3:05 PM, Hal Murray  wrote:
> >
> >
> > preilley_...@comcast.net said:
> >> When I installed power plants in the 1970's they has a special "clock"
> that
> >> showed the cumulative error in terms of clock time.
> >
> > How big were the grids back then?
> >
> > What was the typical range of error over a day or month?
> >
> >
> >> If the generator ran a little too fast the clock would move forward.
> As
> >> the operator observed the clock moving away from zero he would reduce
> the
> >> plant's  power and the clock would move backward toward zero.  ...
> >
> > Does that operator control a single generator or a whole grid?
> >
> > Does having a human in the loop help the control loop stability?
> >
> >
> >
> > --
> > These are my opinions.  I hate spam.
> >
> >
> >
> > ___
> > time-nuts mailing list -- time-nuts@febo.com
> > To unsubscribe, go to https://www.febo.com/cgi-bin/
> mailman/listinfo/time-nuts
> > and follow the instructions there.
>
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> mailman/listinfo/time-nuts
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>
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Re: [time-nuts] Line Frequeny Stablity

[Bob Bownes]

In college we had a Vax 11/730 that would freak out and reboot the same time 
every day. Turns out the culprit was the sync pulses put on the AC for 
synchronizing the classroom clocks...But it took DEC a few weeks to find the 
culprit. 

> On Apr 5, 2017, at 17:12, Bob kb8tq  wrote:
> 
> Hi
> 
> Back in high school, one of the radio club members figured out that the 
> “clock adjustment” took place 
> locally between 4:30 and 5:00 PM. Needless to say, pretty much everybody 
> spent the next week listening 
> to WWV and watching the clock’s second hand go out of sync with the beeps. 
> This was back in the  late 1960’s 
> and the idea of a grid was a bit looser than it is today. Indeed it was post 
> 1964 so there *were* grids big 
> enough to take out the whole north east section of the US. Since we were very 
> much in that area the 
> topic of grid sync came up. Nobody ever really had a good answer to that 
> question. That included the 
> guys who ran the local power company. 
> 
> Bob
> 
>> On Apr 5, 2017, at 3:05 PM, Hal Murray  wrote:
>> 
>> 
>> preilley_...@comcast.net said:
>>> When I installed power plants in the 1970's they has a special "clock"  that
>>> showed the cumulative error in terms of clock time.
>> 
>> How big were the grids back then?
>> 
>> What was the typical range of error over a day or month?
>> 
>> 
>>> If the generator ran a little too fast the clock would move forward.As
>>> the operator observed the clock moving away from zero he would reduce the
>>> plant's  power and the clock would move backward toward zero.  ...
>> 
>> Does that operator control a single generator or a whole grid?
>> 
>> Does having a human in the loop help the control loop stability?
>> 
>> 
>> 
>> -- 
>> These are my opinions.  I hate spam.
>> 
>> 
>> 
>> ___
>> time-nuts mailing list -- time-nuts@febo.com
>> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
>> and follow the instructions there.
> 
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Re: [time-nuts] Line Frequeny Stablity

[Bob kb8tq]

Hi

Back in high school, one of the radio club members figured out that the “clock 
adjustment” took place 
locally between 4:30 and 5:00 PM. Needless to say, pretty much everybody spent 
the next week listening 
to WWV and watching the clock’s second hand go out of sync with the beeps. This 
was back in the  late 1960’s 
and the idea of a grid was a bit looser than it is today. Indeed it was post 
1964 so there *were* grids big 
enough to take out the whole north east section of the US. Since we were very 
much in that area the 
topic of grid sync came up. Nobody ever really had a good answer to that 
question. That included the 
guys who ran the local power company. 

Bob

> On Apr 5, 2017, at 3:05 PM, Hal Murray  wrote:
> 
> 
> preilley_...@comcast.net said:
>> When I installed power plants in the 1970's they has a special "clock"  that
>> showed the cumulative error in terms of clock time.
> 
> How big were the grids back then?
> 
> What was the typical range of error over a day or month?
> 
> 
>> If the generator ran a little too fast the clock would move forward.As
>> the operator observed the clock moving away from zero he would reduce the
>> plant's  power and the clock would move backward toward zero.  ...
> 
> Does that operator control a single generator or a whole grid?
> 
> Does having a human in the loop help the control loop stability?
> 
> 
> 
> -- 
> These are my opinions.  I hate spam.
> 
> 
> 
> ___
> time-nuts mailing list -- time-nuts@febo.com
> To unsubscribe, go to https://www.febo.com/cgi-bin/mailman/listinfo/time-nuts
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Re: [time-nuts] Line Frequeny Stablity

[jimlux]

On 4/5/17 11:13 AM, Bill Hawkins wrote:

The rotary generators in a system of connected generators are
synchronous
machines. There is no frequency difference between them, only phase
angle,
and not much of that - if the system is stable.




Yes.. basically a bunch of coupled oscillators, and unlike the cool 
demos with a bunch of metronomes on a table that self sync, the coupling 
factors among oscillators are not all the same, and the damping of each 
oscillator is different.


Managed historically by people turning a knob and relying on the large 
mass (both literally and figuratively) keeping it from going awry.
If you mess up too much, you get a trip and your generator is offline, 
suddenly, with no load.


Long transmission lines (1000s of km) cause real problems because they 
have time delay that is a significant fraction of a cycle.
So now you have coupled oscillators connected by a transmission line 
(with the characteristics of that transmission line time varying, to a 
certain extent).


Computerized Dispatch (which is what the process of coordinating the 
generation and load is) has been around since the 1960s, but it's not 
perfect.



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Re: [time-nuts] Line Frequeny Stablity

[Hal Murray]

preilley_...@comcast.net said:
> When I installed power plants in the 1970's they has a special "clock"  that
> showed the cumulative error in terms of clock time.

How big were the grids back then?

What was the typical range of error over a day or month?


> If the generator ran a little too fast the clock would move forward.As
> the operator observed the clock moving away from zero he would reduce the
> plant's  power and the clock would move backward toward zero.  ...

Does that operator control a single generator or a whole grid?

Does having a human in the loop help the control loop stability?



-- 
These are my opinions.  I hate spam.



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Re: [time-nuts] Line Frequeny Stablity

[Bill Hawkins]

The rotary generators in a system of connected generators are
synchronous
machines. There is no frequency difference between them, only phase
angle,
and not much of that - if the system is stable.

The ocean liner analogy is correct, as there is only one captain
directing
the ship's course. If each plant set its own power levels it would be
very
difficult to maintain stability, due to the springiness of long
transmission
lines.

A set of connected generators is controlled by regional dispatchers, who
tell their plants how much power to generate in order for the day to
average
out to 60.000 cycles per second. They count cycles instead of measuring
the
frequency. You can count cycles with a synchronous clock.

This becomes less tidy when DC tie lines are used, because inverters
have
to be adjusted to get the correct power flow.

Hope I got most of that right.

Bill Hawkins


-Original Message-
From: time-nuts [mailto:time-nuts-boun...@febo.com] On Behalf Of Peter
Reilley
Sent: Wednesday, April 05, 2017 7:42 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] Line Frequeny Stablity

Think of it as an ocean liner trying to keep a dead straight course to
it's destination.
It weighs many tons and wind and waves may drive it off it's path but
the captain
can correct for this.   It eventually arrives at it's destination and is

only a few feet
from the dock.

The total rotating mass of all the generators in a network is many times
the mass of an
ocean liner.   The operators do their best to keep them running at the 
correct frequency.
Unexpected load changes can cause some divergence, but over time the
average is dead on.

When I installed power plants in the 1970's they has a special "clock" 
that showed the
cumulative error in terms of clock time.   The clock had two inputs, one

from the utility
power and the other from some reference, possibly WWV.   Normally the 
"clock" was
pointing up at zero and not moving.

If the generator ran a little too fast the clock would move forward.   
As the operator
observed the clock moving away from zero he would reduce the plant's
power and the
clock would move backward toward zero.   His goal was to keep the clock 
at zero and
not moving.   Thus, your bedside clock was always on time even if there 
were temporary
excursions fast or slow.

Pete.


On 4/4/2017 5:28 PM, Thomas D. Erb wrote:
> Thanks for the info.
>
>
> So that tells me how data is recorded - but not how the frequency is
kept stable ?
>
> Is the line frequency now directly tied to GPS clock - with no drift ?
>
> Thomas D. Erb
> t...@electrictime.com<mailto:t...@electrictime.com> / Electric Time 
> Company, Inc.
> Office: 508-359-4396 x 117 / Fax: 508-359-4482
> 97 West Street Medfield, MA 02052 USA

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Re: [time-nuts] Line Frequeny Stablity

[Scott Stobbe]

I would guess the tightest control loop is on the generator stator field
windings, with mechanical control being secondary. Definitely a lot of
poles and zeros to worry about.

On Wed, Apr 5, 2017 at 9:01 AM, jimlux  wrote:

> On 4/4/17 2:28 PM, Thomas D. Erb wrote:
>
>> Thanks for the info.
>>
>>
>> So that tells me how data is recorded - but not how the frequency is kept
>> stable ?
>>
>> Is the line frequency now directly tied to GPS clock - with no drift ?
>>
>
> The line frequency is adjusted, for the most part, by adjusting the prime
> power (steam valves, dam penstocks, etc.) on the generators at power
> stations. That changes the speed, slightly, although as generator 1 of N
> starts to get ahead, the electrical load increases, and it slows down.
>
> It's actually a pretty complex system, since there are a whole raft of
> "spring constants" in between the multiple generators in a system, there's
> phase shifts due to transmission line inductance and capacitance.
>
> "Stabilizing" a system in the face of changing demand is a non-trivial
> task.
>
>
>
>
>
>
>
>> Thomas D. Erb
>> t...@electrictime.com /
>> Electric Time Company, Inc.
>> Office: 508-359-4396 x 117 / Fax: 508-359-4482
>> 97 West Street Medfield, MA 02052 USA
>> www.electrictime.com
>> [Facebook]> Company-Inc/127918073950854?ref=hl>[Twitter]> twitter.com/tower_clocks>[pinterest]> pinterest.com/electrictime/>
>> [htmlsig.com]
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Re: [time-nuts] Line Frequeny Stablity

[David]

I have seen some proposals to require VAR capability in photoelectric
installations but how feasible is that?  I cannot imagine utility
customers being pleased with having to pay extra for such a nebulous
to them capability.

I could see the utility companies pushing it as a requirement in lieu
of installing banks of synchronous condensers.  Maybe this could be
integrated with net metering so that users get paid for providing VAR
correction and pay for VARs but I bet it would be politically
infeasible.

Thinking about the stability problems associated with distributed
generation gives me a headache.  I am inclined to believe that any
solution which relies on central management or timing is an invitation
to major failure.

On Wed, 5 Apr 2017 09:52:32 +0200, you wrote:

>...
>
>Until recently, photoelectric would not provide any of the rotating iron 
>properties, but the increase popularity of it now requires it to start 
>to have such properties for the stability of the system.
>
>Cheers,
>Magnus
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Re: [time-nuts] Line Frequeny Stablity

[Peter Reilley]

The response time in a large plant is very slow.   Large steam plants 
running at steady
state are running with their steam valves wide open.   A partially 
closed valve is an energy

loss and is only used when changes occur.

The power control for a plant running at a steady load is the amount of 
fuel thrown into
the boiler.   When you want more power you shoot more gas, oil, or coal 
into the boiler.
For a nuke you pull the control rods.   Behind all of this is a lot of 
thermal mass.   Things

don't change quickly.

Pete.

On 4/5/2017 9:01 AM, jimlux wrote:

On 4/4/17 2:28 PM, Thomas D. Erb wrote:

Thanks for the info.


So that tells me how data is recorded - but not how the frequency is 
kept stable ?


Is the line frequency now directly tied to GPS clock - with no drift ?


The line frequency is adjusted, for the most part, by adjusting the 
prime power (steam valves, dam penstocks, etc.) on the generators at 
power stations. That changes the speed, slightly, although as 
generator 1 of N starts to get ahead, the electrical load increases, 
and it slows down.


It's actually a pretty complex system, since there are a whole raft of 
"spring constants" in between the multiple generators in a system, 
there's phase shifts due to transmission line inductance and capacitance.


"Stabilizing" a system in the face of changing demand is a non-trivial 
task.








Thomas D. Erb
t...@electrictime.com /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com
[Facebook][Twitter][pinterest] 


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Re: [time-nuts] Line Frequeny Stablity

[jimlux]

On 4/4/17 2:28 PM, Thomas D. Erb wrote:

Thanks for the info.


So that tells me how data is recorded - but not how the frequency is kept 
stable ?

Is the line frequency now directly tied to GPS clock - with no drift ?


The line frequency is adjusted, for the most part, by adjusting the 
prime power (steam valves, dam penstocks, etc.) on the generators at 
power stations. That changes the speed, slightly, although as generator 
1 of N starts to get ahead, the electrical load increases, and it slows 
down.


It's actually a pretty complex system, since there are a whole raft of 
"spring constants" in between the multiple generators in a system, 
there's phase shifts due to transmission line inductance and capacitance.


"Stabilizing" a system in the face of changing demand is a non-trivial task.







Thomas D. Erb
t...@electrictime.com /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com
[Facebook][Twitter][pinterest]
[htmlsig.com]
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Re: [time-nuts] Line Frequeny Stablity

[Peter Reilley]

Think of it as an ocean liner trying to keep a dead straight course to 
it's destination.
It weighs many tons and wind and waves may drive it off it's path but 
the captain
can correct for this.   It eventually arrives at it's destination and is 
only a few feet

from the dock.

The total rotating mass of all the generators in a network is many times 
the mass of an
ocean liner.   The operators do their best to keep them running at the 
correct frequency.
Unexpected load changes can cause some divergence, but over time the 
average is

dead on.

When I installed power plants in the 1970's they has a special "clock" 
that showed the
cumulative error in terms of clock time.   The clock had two inputs, one 
from the utility
power and the other from some reference, possibly WWV.   Normally the 
"clock" was

pointing up at zero and not moving.

If the generator ran a little too fast the clock would move forward.   
As the operator
observed the clock moving away from zero he would reduce the plant's 
power and the
clock would move backward toward zero.   His goal was to keep the clock 
at zero and
not moving.   Thus, your bedside clock was always on time even if there 
were temporary

excursions fast or slow.

Pete.


On 4/4/2017 5:28 PM, Thomas D. Erb wrote:

Thanks for the info.


So that tells me how data is recorded - but not how the frequency is kept 
stable ?

Is the line frequency now directly tied to GPS clock - with no drift ?

Thomas D. Erb
t...@electrictime.com /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com
[Facebook][Twitter][pinterest]
[htmlsig.com]
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Re: [time-nuts] Line Frequeny Stablity

[Magnus Danielson]

Hi,

Ok, quick intro to the frequency steering.

There still remains rules that say that network frequency should be on 
average 60 Hz on the US grid. (Yes, there is proposals to remove it, but 
it is still effective.)


Since the generation (let's talk traditional here not to make things 
more complex than they need to be for the first overview) is from 
generators, essentially big rotating lumps of iron, the balance between 
load and generation causes the frequency change. If you have more load 
than generation, the frequency will lower while if you have more 
generation than load the frequency will go up. Essentially, if you 
undergenerate, you would need the rotating energy of the lumps of load 
to deliver, but that reduces their speed and if you underconsume the 
energy goes into the rotation of the lumps.


Now, by monitoring the frequency you can steer the balance, askning 
hydropower to increase or decrease production to balance the shift of 
load. The operators have a fair clue on how the day will proceed as 
people wake up, industry starts, workday, industry closes down, people 
get home etc, so there is a basic pattern there to give a clue, but they 
monitor it and balance it.


By also balance the phase, you can know how much you lag behind and 
needs to run up by running the frequency high. This require spending 
energy by increasing production compared to the load. Now, by being 
smart you do that when you have low load, so that you don't have to 
spend as much energy to achieve it, but never the less.


Then you have to manage your reactive energy, the VAr, which is a 
different matter.


Breakers have several form of catastrophic protections in them, among 
those if the frequency goes bad. Turns out that the frequency monitoring 
of breakers gives so diverse readings such that for post mortem 
analysis, they provide bogus values. They learned this the hard way 
after the North-Eastern Blackout. When they threw out all the 
traditional frequency readings, the PMU data that remained painted a 
consistent picture.


The detailed monitoring of PMU gives much more data, also illustrates 
forced oscillation, inter-area-oscillations etc. which makes the phase 
wobble in interesting ways, and when analyzed gives good clues about 
problems in the network.


An even more "fun" scenario is when the network runs into islanding, 
since the link between areas is to weak to keep the frequency at the 
same rate, i.e. the link is to weak to support the load, so one part has 
overload and goes down in frequency while the other have overproduction 
and gos high in frequency, which you can see by the way that phase 
starts to deviate between the networks, and that before you have the de 
facto islanding.


The islanding illustrates the need of the links to be strong enough so 
that generators synchronize, or should we say syntonize to be correct 
with terms, that is, they have the same rate.


The four islands that you identified do their own independent frequency 
steering, but they exchange power. The generation-load thing still 
happens, but phase/frequency decoupled. HVDC cables achieve the same thing.


Anyway, phase monitoring has become a very good tool for so many of 
these measurements, and that requires a common "reference" phase and 
that is GPS. That helps to monitor the phase and frequency of the grid 
so that it can be controlled.


A peculiarity of the field is the ROCOF - Rate Of Change OF Frequency. 
This is what we call linear frequency drift. Looking on those numbers 
give you a good hint where you are going.


Until recently, photoelectric would not provide any of the rotating iron 
properties, but the increase popularity of it now requires it to start 
to have such properties for the stability of the system.


Cheers,
Magnus

On 04/04/2017 11:28 PM, Thomas D. Erb wrote:

Thanks for the info.


So that tells me how data is recorded - but not how the frequency is kept 
stable ?

Is the line frequency now directly tied to GPS clock - with no drift ?

Thomas D. Erb
t...@electrictime.com /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com
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Re: [time-nuts] Line Frequeny Stablity

[Thomas D. Erb]

Thanks for the info.


So that tells me how data is recorded - but not how the frequency is kept 
stable ?

Is the line frequency now directly tied to GPS clock - with no drift ?

Thomas D. Erb
t...@electrictime.com /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com
[Facebook][Twitter][pinterest]
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Re: [time-nuts] Line Frequeny Stablity

[Magnus Danielson]

Hi,

It's based on UTC, as derived from GPS.

I think you will find the following NASPI report of interest:
https://www.naspi.org/node/608

You will find maps over the regions too!

While NASPI is PMU/synchro-phasor focused, older equipment use GPS too 
for phase capture.


Cheers,
Magnus

On 04/04/2017 03:33 PM, Thomas D. Erb wrote:

I was wondering if anyone knew how the US power grids control their line 
frequency with respect to time ?


There seems to be four separate grids - Eastern, Texas, Western and Quebec - 
but I have no idea how they get their time.






Thomas D. Erb
t...@electrictime.com /
Electric Time Company, Inc.
Office: 508-359-4396 x 117 / Fax: 508-359-4482
97 West Street Medfield, MA 02052 USA
www.electrictime.com
[Facebook][Twitter][pinterest]
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