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James Wilkinson Sword
Guest

Sat Mar 18, 2017 6:02 am   



https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident

Can someone explain why a power station should disconnect due to detecting a small frequency drop? Would this not make things worse?

--
If you jog in a jogging suit, lounge in lounging pyjamas, and smoke in a smoking jacket, why would anyone want to wear a windbreaker?

rickman
Guest

Sat Mar 18, 2017 7:30 am   



On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
Quote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident


Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?


When I read that article, it said that this was no longer the rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

--

Rick C

James Wilkinson Sword
Guest

Sat Mar 18, 2017 7:30 am   



On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

Quote:
On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident


Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.


Agreed. But if a power station detects the grid is at a slightly low frequency, why on earth would it be a good idea to cease generating? The low frequency was presumably caused by a lack of input, making the power stations throughout the country labour a little and slow down. Taking more power stations off the grid will exacerbate the problem.

--
I got invited to a Muslim party the other night.
It was the fastest game of pass the parcel I've even seen!

rickman
Guest

Sat Mar 18, 2017 7:30 am   



On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
Quote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident



Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed. But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.


Did you read what I wrote? That is not the rule.

--

Rick C

James Wilkinson Sword
Guest

Sat Mar 18, 2017 7:30 am   



On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

Quote:
On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident



Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed. But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote? That is not the rule.


It is, just that the rule has changed the amount of frequency allowed to change before tripping occurs.

--
"I went to a fight the other night and a hockey game broke out." -- Rodney Dangerfield.

James Wilkinson Sword
Guest

Mon Mar 20, 2017 7:30 am   



On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

Quote:
On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident



Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed. But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote? That is not the rule.


Yes, you said they seperate if the frequency is wrong. Which is not a good idea is it?

--
Sit on my lap, and we'll talk about the first thing that comes up.

Daniel60
Guest

Tue Dec 05, 2017 3:13 pm   



James Wilkinson Sword wrote:
Quote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident




Can someone explain why a power station should disconnect due to
detecting a small frequency drop?  Would this not make things worse?

When I read that article, it said that this was no longer the rule.  In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point.  They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule
is to
separate portions of the grid when things are going wonky.  I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed.  But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote?  That is not the rule.

Yes, you said they seperate if the frequency is wrong.  Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....


It would seem to me that if the freqs that two generators were operating
at were slightly different, then the instantaneous voltages being
produced by the two generators would also be different, so one generator
would be supplying power to the "real" load *and* to the slower generator!

Daniel

James Wilkinson Sword
Guest

Tue Dec 05, 2017 3:20 pm   



On Tue, 05 Dec 2017 13:13:41 -0000, Daniel60 <daniel47_at_eternal-september.org> wrote:

Quote:
James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident




Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule
is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed. But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote? That is not the rule.

Yes, you said they seperate if the frequency is wrong. Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....

It would seem to me that if the freqs that two generators were operating
at were slightly different, then the instantaneous voltages being
produced by the two generators would also be different, so one generator
would be supplying power to the "real" load *and* to the slower generator!


Which would speed it up a little.

--
We were supposed to have flying cars in the 21st century.
The Internet is cool, but I'd rather have a flying car.

rickman
Guest

Tue Dec 05, 2017 11:24 pm   



Daniel60 wrote on 12/5/2017 8:13 AM:
Quote:
James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident




Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed. But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote? That is not the rule.

Yes, you said they seperate if the frequency is wrong. Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....

It would seem to me that if the freqs that two generators were operating at
were slightly different, then the instantaneous voltages being produced by
the two generators would also be different, so one generator would be
supplying power to the "real" load *and* to the slower generator!


Keep in mind that the power lost in transmission is not zero. A
sufficiently small difference in phase (rather than frequency which would
result in phase creeping) would simply result in a smaller or larger loss in
the transmission. Given the difference in phase of voltage on the load this
would result in current leading or lagging the generated voltage and result
in a torque that would speed the lagging generator and slow the leading
generator since the back EMF is created by the current.

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

Daniel60
Guest

Wed Dec 06, 2017 8:10 am   



rickman wrote:
Quote:
Daniel60 wrote on 12/5/2017 8:13 AM:
James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident





Can someone explain why a power station should disconnect due to
detecting a small frequency drop?  Would this not make things worse?

When I read that article, it said that this was no longer the
rule.  In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point.  They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule
is to
separate portions of the grid when things are going wonky.  I can
only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed.  But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote?  That is not the rule.

Yes, you said they seperate if the frequency is wrong.  Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....

It would seem to me that if the freqs that two generators were
operating at
were slightly different, then the instantaneous voltages being
produced by
the two generators would also be different, so one generator would be
supplying power to the "real" load *and* to the slower generator!

Keep in mind that the power lost in transmission is not zero.  A
sufficiently small difference in phase (rather than frequency which
would result in phase creeping) would simply result in a smaller or
larger loss in the transmission.  Given the difference in phase of
voltage on the load this would result in current leading or lagging the
generated voltage and result in a torque that would speed the lagging
generator and slow the leading generator since the back EMF is created
by the current.

If one generator was running at 50Hz and the other was running at, say,
49.95Hz, then every1,000 cycles or so, the two waveforms would be
exactly in phase ..... for an infinitesimally (??Sp) small time!!

If the two generators were both running at 50Hz but one lagged the other
by some degrees (your second case, and not the one I originally
considered) could possibly be as you mentioned.

Daniel

rickman
Guest

Wed Dec 06, 2017 1:27 pm   



Daniel60 wrote on 12/6/2017 1:10 AM:
Quote:
rickman wrote:
Daniel60 wrote on 12/5/2017 8:13 AM:
James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident





Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed. But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote? That is not the rule.

Yes, you said they seperate if the frequency is wrong. Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....

It would seem to me that if the freqs that two generators were operating at
were slightly different, then the instantaneous voltages being produced by
the two generators would also be different, so one generator would be
supplying power to the "real" load *and* to the slower generator!

Keep in mind that the power lost in transmission is not zero. A
sufficiently small difference in phase (rather than frequency which would
result in phase creeping) would simply result in a smaller or larger loss
in the transmission. Given the difference in phase of voltage on the load
this would result in current leading or lagging the generated voltage and
result in a torque that would speed the lagging generator and slow the
leading generator since the back EMF is created by the current.

If one generator was running at 50Hz and the other was running at, say,
49.95Hz, then every1,000 cycles or so, the two waveforms would be exactly in
phase ..... for an infinitesimally (??Sp) small time!!

If the two generators were both running at 50Hz but one lagged the other by
some degrees (your second case, and not the one I originally considered)
could possibly be as you mentioned.


The point is that neither of these two cases are realistic because the
frequency is never perfectly stable. That's the point, the whole grid is a
living, breathing entity and every part responds to the rest in a way that
tends to lock it together. Talking about two generators being some small
amount different in frequency for any length of time won't last, they will
be pushed together.

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

James Wilkinson Sword
Guest

Wed Dec 06, 2017 7:09 pm   



On Wed, 06 Dec 2017 11:27:40 -0000, rickman <gnuarm_at_gmail.com> wrote:

Quote:
Daniel60 wrote on 12/6/2017 1:10 AM:
rickman wrote:
Daniel60 wrote on 12/5/2017 8:13 AM:
James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident





Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed. But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote? That is not the rule.

Yes, you said they seperate if the frequency is wrong. Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....

It would seem to me that if the freqs that two generators were operating at
were slightly different, then the instantaneous voltages being produced by
the two generators would also be different, so one generator would be
supplying power to the "real" load *and* to the slower generator!

Keep in mind that the power lost in transmission is not zero. A
sufficiently small difference in phase (rather than frequency which would
result in phase creeping) would simply result in a smaller or larger loss
in the transmission. Given the difference in phase of voltage on the load
this would result in current leading or lagging the generated voltage and
result in a torque that would speed the lagging generator and slow the
leading generator since the back EMF is created by the current.

If one generator was running at 50Hz and the other was running at, say,
49.95Hz, then every1,000 cycles or so, the two waveforms would be exactly in
phase ..... for an infinitesimally (??Sp) small time!!

If the two generators were both running at 50Hz but one lagged the other by
some degrees (your second case, and not the one I originally considered)
could possibly be as you mentioned.

The point is that neither of these two cases are realistic because the
frequency is never perfectly stable. That's the point, the whole grid is a
living, breathing entity and every part responds to the rest in a way that
tends to lock it together. Talking about two generators being some small
amount different in frequency for any length of time won't last, they will
be pushed together.


Indeed, and presumably also if they're a little out of phase permanently. Although presumably there's a limit. If I brought up my generator 180 degrees out of phase with the grid, something bad would happen - melted coils? I think what happens with power stations is they use the grid to spin up the generator before introducing it's own fuel.

--
Auctioneer, n. The man who proclaims with a hammer that he has picked a pocket with his tongue.

rickman
Guest

Thu Dec 07, 2017 1:20 am   



James Wilkinson Sword wrote on 12/6/2017 12:09 PM:
Quote:
On Wed, 06 Dec 2017 11:27:40 -0000, rickman <gnuarm_at_gmail.com> wrote:

Daniel60 wrote on 12/6/2017 1:10 AM:
rickman wrote:
Daniel60 wrote on 12/5/2017 8:13 AM:
James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident






Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the
rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule
is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed. But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote? That is not the rule.

Yes, you said they seperate if the frequency is wrong. Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....

It would seem to me that if the freqs that two generators were
operating at
were slightly different, then the instantaneous voltages being produced by
the two generators would also be different, so one generator would be
supplying power to the "real" load *and* to the slower generator!

Keep in mind that the power lost in transmission is not zero. A
sufficiently small difference in phase (rather than frequency which would
result in phase creeping) would simply result in a smaller or larger loss
in the transmission. Given the difference in phase of voltage on the load
this would result in current leading or lagging the generated voltage and
result in a torque that would speed the lagging generator and slow the
leading generator since the back EMF is created by the current.

If one generator was running at 50Hz and the other was running at, say,
49.95Hz, then every1,000 cycles or so, the two waveforms would be exactly in
phase ..... for an infinitesimally (??Sp) small time!!

If the two generators were both running at 50Hz but one lagged the other by
some degrees (your second case, and not the one I originally considered)
could possibly be as you mentioned.

The point is that neither of these two cases are realistic because the
frequency is never perfectly stable. That's the point, the whole grid is a
living, breathing entity and every part responds to the rest in a way that
tends to lock it together. Talking about two generators being some small
amount different in frequency for any length of time won't last, they will
be pushed together.

Indeed, and presumably also if they're a little out of phase permanently.
Although presumably there's a limit. If I brought up my generator 180
degrees out of phase with the grid, something bad would happen - melted
coils? I think what happens with power stations is they use the grid to
spin up the generator before introducing it's own fuel.


I have read they just spin it up by the power source and adjust the
speed/frequency and phase to match the grid as much as possible before
connecting it to the grid.

The real issue is how does it all remain stable with so many points each
trying to do its own thing but responding to the grid? I think of it as a
flock of birds. No one bird controls how the flock moves, but they will
part and dodge to avoid a hawk diving in to take one because in essence,
they are all connected in a grid.

--

Rick C

Viewed the eclipse at Wintercrest Farms,
on the centerline of totality since 1998

Daniel60
Guest

Thu Dec 07, 2017 2:29 pm   



rickman wrote:
Quote:
Daniel60 wrote on 12/6/2017 1:10 AM:
rickman wrote:
Daniel60 wrote on 12/5/2017 8:13 AM:
James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com
wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident






Can someone explain why a power station should disconnect due to
detecting a small frequency drop?  Would this not make things
worse?

When I read that article, it said that this was no longer the
rule.  In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at
that
point.  They were running old software.

I assume that not entirely unlike blowing a fuse, the general
rule is to
separate portions of the grid when things are going wonky.  I
can only
imagine that there could be parts of the grid damaged if the
flow of
power is not well regulated.

Agreed.  But if a power station detects the grid is at a slightly
low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input,
making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote?  That is not the rule.

Yes, you said they seperate if the frequency is wrong.  Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....

It would seem to me that if the freqs that two generators were
operating at
were slightly different, then the instantaneous voltages being
produced by
the two generators would also be different, so one generator would be
supplying power to the "real" load *and* to the slower generator!

Keep in mind that the power lost in transmission is not zero.  A
sufficiently small difference in phase (rather than frequency which
would
result in phase creeping) would simply result in a smaller or larger
loss
in the transmission.  Given the difference in phase of voltage on the
load
this would result in current leading or lagging the generated voltage
and
result in a torque that would speed the lagging generator and slow the
leading generator since the back EMF is created by the current.

If one generator was running at 50Hz and the other was running at, say,
49.95Hz, then every1,000 cycles or so, the two waveforms would be
exactly in
phase ..... for an infinitesimally (??Sp) small time!!

If the two generators were both running at 50Hz but one lagged the
other by
some degrees (your second case, and not the one I originally considered)
could possibly be as you mentioned.

The point is that neither of these two cases are realistic because the
frequency is never perfectly stable.  That's the point, the whole grid
is a living, breathing entity and every part responds to the rest in a
way that tends to lock it together.  Talking about two generators being
some small amount different in frequency for any length of time won't
last, they will be pushed together.

Thanks for the memories!!


As I was sitting here, catching up on these posts, I recalled, back
about 40 years ago (in another life Wink ), I worked at an Australian
Army H.F. Transmitter site where, each Tuesday, we would test out our
on-site, (3) 300KVA Blackstone generators by bring up one of them,
syncing it to the mains supply, disconnecting the mains and then, a
couple of hours later, bring up another gennie, sync it to the first
one, then drop the first one off-line, and then a couple of hours later,
sync this gennie back to the mains.

All good fun!!

Daniel

James Wilkinson Sword
Guest

Thu Dec 07, 2017 6:26 pm   



On Wed, 06 Dec 2017 23:20:58 -0000, rickman <gnuarm_at_gmail.com> wrote:

Quote:
James Wilkinson Sword wrote on 12/6/2017 12:09 PM:
On Wed, 06 Dec 2017 11:27:40 -0000, rickman <gnuarm_at_gmail.com> wrote:

Daniel60 wrote on 12/6/2017 1:10 AM:
rickman wrote:
Daniel60 wrote on 12/5/2017 8:13 AM:
James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:37:53 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 10:28 PM, James Wilkinson Sword wrote:
On Sat, 18 Mar 2017 02:01:09 -0000, rickman <gnuarm_at_gmail.com> wrote:

On 3/17/2017 8:02 PM, James Wilkinson Sword wrote:
https://en.wikipedia.org/wiki/National_Grid_(Great_Britain)#May_2008_incident






Can someone explain why a power station should disconnect due to
detecting a small frequency drop? Would this not make things worse?

When I read that article, it said that this was no longer the
rule. In
fact, the problem was caused by some smaller generation facilities
tripping off the grid when the current rule was to *not* trip at that
point. They were running old software.

I assume that not entirely unlike blowing a fuse, the general rule
is to
separate portions of the grid when things are going wonky. I can only
imagine that there could be parts of the grid damaged if the flow of
power is not well regulated.

Agreed. But if a power station detects the grid is at a slightly low
frequency, why on earth would it be a good idea to cease generating?
The low frequency was presumably caused by a lack of input, making the
power stations throughout the country labour a little and slow down.
Taking more power stations off the grid will exacerbate the problem.

Did you read what I wrote? That is not the rule.

Yes, you said they seperate if the frequency is wrong. Which is not a
good idea is it?

Coming in very, very, late to this discussion, but .....

It would seem to me that if the freqs that two generators were
operating at
were slightly different, then the instantaneous voltages being produced by
the two generators would also be different, so one generator would be
supplying power to the "real" load *and* to the slower generator!

Keep in mind that the power lost in transmission is not zero. A
sufficiently small difference in phase (rather than frequency which would
result in phase creeping) would simply result in a smaller or larger loss
in the transmission. Given the difference in phase of voltage on the load
this would result in current leading or lagging the generated voltage and
result in a torque that would speed the lagging generator and slow the
leading generator since the back EMF is created by the current.

If one generator was running at 50Hz and the other was running at, say,
49.95Hz, then every1,000 cycles or so, the two waveforms would be exactly in
phase ..... for an infinitesimally (??Sp) small time!!

If the two generators were both running at 50Hz but one lagged the other by
some degrees (your second case, and not the one I originally considered)
could possibly be as you mentioned.

The point is that neither of these two cases are realistic because the
frequency is never perfectly stable. That's the point, the whole grid is a
living, breathing entity and every part responds to the rest in a way that
tends to lock it together. Talking about two generators being some small
amount different in frequency for any length of time won't last, they will
be pushed together.

Indeed, and presumably also if they're a little out of phase permanently.
Although presumably there's a limit. If I brought up my generator 180
degrees out of phase with the grid, something bad would happen - melted
coils? I think what happens with power stations is they use the grid to
spin up the generator before introducing it's own fuel.

I have read they just spin it up by the power source and adjust the
speed/frequency and phase to match the grid as much as possible before
connecting it to the grid.

The real issue is how does it all remain stable with so many points each
trying to do its own thing but responding to the grid? I think of it as a
flock of birds. No one bird controls how the flock moves, but they will
part and dodge to avoid a hawk diving in to take one because in essence,
they are all connected in a grid.


Any bird flying slightly too fast will adjust itself as it comes too close to the next. Any generator spinning slightly too fast will have a bigger current drawn to push the others, so it will slow and the others will speed up.


--
If I said you had a beautiful body, would you hold it against me? -- Monty Python, Episode 25

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