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| Author |
Power Station Grid Synchronization
|
|
| lekosmoth@yahoo.com 2007-02-14, 5:25 pm |
| Hi,
I am trying to learn more about synchronizing a mini power station to
a national grid network. Can someone recommend a good book that
explains this. And what are the equipments used here and who
manufacturers these products?
Thanking you in advance.
LS
| |
| dave.walters@comcast.net 2007-02-14, 5:25 pm |
| On Feb 14, 11:58 am, lekosm...@yahoo.com wrote:
> Hi,
>
> I am trying to learn more about synchronizing a mini power station to
> a national grid network. Can someone recommend a good book that
> explains this. And what are the equipments used here and who
> manufacturers these products?
>
> Thanking you in advance.
>
> LS
I can explain it simply enough.
The AC power coming from *any* electrical power source is in 3 phases.
Each phase is 120 degrees out from each other. They are called "A" "B"
and "C" Phases.
In order to "parallel" the 3 phases, each A-B-C phase for your power
source (wheather it's 100 watts or 1,000 megawatts, it makes no
difference) has to be in "syncronization" with A-B-C phases of the
system, which all work in harmony, from Hudson bay to northern Baja
California.
In large units, we do this manually (and now, automically) by using
what's called a 'synch' scope with a rotating arm (representing the
phase angle of the 3 phases as one, in relationship to the phase
angles of the sytsem. When they are at "unity", that is the arrow on
the meter facing straight up, we close the paralleling breaker. When
this happens the system "grabs", quite literaly, our generator and the
3 phase angles move in harmony/synchronization. The 'speed' of the
turbine/generator, wheter 1800 RPMs or 3600 RPMs is then forced driven
by the system and not your primary energy source (steam). No matter
how much more steam (or water as in hydro) you add, the speed with
always stay the same. Which is how power is increased because the
steam, while not adding speed, adds torque, which, by increasing the
DC field, increases megawatts.
In smaller units' such as a DC solar panel collection or small hydro
unit, for a home, with say, 3,600 watts (about average usage at peak
time around 7pm in most places) this can be done electronically at the
inverter. You need the inverter to take the DC and make it AC so the
toys in your house can actually use the solar energy...and the
inverter is needed to allow exess energy to flow *back into the
system* and run yoru meter in a backward direction! The inverters that
do this are actually more sophisticated than the automatic volage
regulator I'm forced to use at my power plant.
David Walters
Control Room Operator
Potrero Power Plant, San Francisco, CA
| |
| zzbunker@netscape.net 2007-02-14, 5:25 pm |
| On Feb 14, 2:58 pm, lekosm...@yahoo.com wrote:
> Hi,
>
> I am trying to learn more about synchronizing a mini power station to
> a national grid network. Can someone recommend a good book that
> explains this. And what are the equipments used here and who
> manufacturers these products?
There are too many misleading texbooks
on the subject to even bother listing.
Since if you noticed the blackouts
in the northeast US over the last
60 years, the "grid" is a complete
fiction, invented by your state
power regulators, not a
national organization of anything.
So the only way to synchrinize
any two pieces of wire is
basically what amounts a high power
phase-locked loop.
>
> Thanking you in advance.
>
> LS
| |
| Don Kelly 2007-02-14, 8:25 pm |
| As for the synchroscope- a set of lights works well. Three sets of 240V
lamps (for 120V systems) connected directly across the breaker, phase a to a
etc will be all bright when out of phase and all dark when in phase and
voltage is close enough -close the breaker. This will not occur when
phasing rotation is wrong. .
Now consider one lamp connected
a-a and the others a-c and a-c and placed in a triangle will give a nice
rotating effect- just be sure that the switching is done when the a-a is
dark.
A major concern is to have the phase rotation correct.
As for the rest of the explanation, there is a technical flaw.
"Which is how power is increased because the steam, while not adding speed,
adds torque, which, by increasing the DC field, increases megawatts."
Tain't true.
Increasing the input power shifts the phase of the machine and this
increases the power output (and does affect speed but this won't normally
be seen if the machine is small with respect to the system) How do you think
that you correct frequency?
It does NOT increase the DC field (an increase in field -through attempts
to raise voltage, will increase reactive output from that machine).
Oh, yes, there are no AC ties from Hudson's Bay to Baja California. Such
ties would be unstable. Even between Alberta (tied to the Northwest power
pool) and Saskatchewan (tied to the Midwest system) there are no AC links.
There are DC, asynchronous links in this case and also a DC backbone link in
the NW system which makes it possible to maintain the links from Western
Canada through to the Baja.
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
<dave.walters@comcast.net> wrote in message
news:1171491408.137155.194410@q2g2000cwa.googlegroups.com...
> On Feb 14, 11:58 am, lekosm...@yahoo.com wrote:
>
> I can explain it simply enough.
>
> The AC power coming from *any* electrical power source is in 3 phases.
> Each phase is 120 degrees out from each other. They are called "A" "B"
> and "C" Phases.
>
> In order to "parallel" the 3 phases, each A-B-C phase for your power
> source (wheather it's 100 watts or 1,000 megawatts, it makes no
> difference) has to be in "syncronization" with A-B-C phases of the
> system, which all work in harmony, from Hudson bay to northern Baja
> California.
>
> In large units, we do this manually (and now, automically) by using
> what's called a 'synch' scope with a rotating arm (representing the
> phase angle of the 3 phases as one, in relationship to the phase
> angles of the sytsem. When they are at "unity", that is the arrow on
> the meter facing straight up, we close the paralleling breaker. When
> this happens the system "grabs", quite literaly, our generator and the
> 3 phase angles move in harmony/synchronization. The 'speed' of the
> turbine/generator, wheter 1800 RPMs or 3600 RPMs is then forced driven
> by the system and not your primary energy source (steam). No matter
> how much more steam (or water as in hydro) you add, the speed with
> always stay the same. >
> In smaller units' such as a DC solar panel collection or small hydro
> unit, for a home, with say, 3,600 watts (about average usage at peak
> time around 7pm in most places) this can be done electronically at the
> inverter. You need the inverter to take the DC and make it AC so the
> toys in your house can actually use the solar energy...and the
> inverter is needed to allow exess energy to flow *back into the
> system* and run yoru meter in a backward direction! The inverters that
> do this are actually more sophisticated than the automatic volage
> regulator I'm forced to use at my power plant.
>
> David Walters
> Control Room Operator
> Potrero Power Plant, San Francisco, CA
>
| |
|
|
| Don Kelly 2007-02-14, 9:25 pm |
| ----------------------------
<zzbunker@netscape.net> wrote in message
news:1171495225.571670.275450@h3g2000cwc.googlegroups.com...
> On Feb 14, 2:58 pm, lekosm...@yahoo.com wrote:
>
> There are too many misleading texbooks
> on the subject to even bother listing.
> Since if you noticed the blackouts
> in the northeast US over the last
> 60 years, the "grid" is a complete
> fiction, invented by your state
> power regulators, not a
> national organization of anything.
> So the only way to synchrinize
> any two pieces of wire is
> basically what amounts a high power
> phase-locked loop.
>
---------
Unfortunately, in phase locking a generator to a system which consists of a
"grid" (which is not a fiction) the result is that the output of the
generator will be 0.
Do not try to apply electronic ideas to a power grid which involves both
mechanical and electrical . They very often , at best, don't work.
Also considering the number of independent variables and non-linearities
involved, electronic systems, including computers, are relatively trivial
and uncomplicated.
Phase locking is the ideal in smoothly synchronising a generator to the grid
BUT once the machine is "on line" it is neither beneficial nor wanted.
Shifting the phase of a generator with regard to the other generators on the
system is necessary for production of power from that generator. Of course
the dynamics of the electrical system and the mechanical systems involved
are factors.
Another case is maximum power transfer:
Maximum power transfer is not a desirable operating strategy from an
efficiency viewpoint or from a stability viewpoint. Not only will it not be
efficient, it would not be a possible operating regime.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
| |
| daestrom 2007-02-14, 9:25 pm |
|
<zzbunker@netscape.net> wrote in message
news:1171495225.571670.275450@h3g2000cwc.googlegroups.com...
> On Feb 14, 2:58 pm, lekosm...@yahoo.com wrote:
>
> There are too many misleading texbooks
> on the subject to even bother listing.
> Since if you noticed the blackouts
> in the northeast US over the last
> 60 years, the "grid" is a complete
> fiction, invented by your state
> power regulators, not a
> national organization of anything.
> So the only way to synchrinize
> any two pieces of wire is
> basically what amounts a high power
> phase-locked loop.
>
So sayeth someone that has probably never brought a generator on-line.
The 'grid' is what it is. A major network of interconnected generation and
load stations. There are actually several 'sections' that are *not*
synchronized, such as the west to east and Texas has it's own 'grid'.
Nevertheless, there are interconnecting points with DC links to allow power
to flow between sections.
A major part of the reason for the blackout in 2003 was 'grid' disturbances
in Ohio, lower Michigan, and Ontario affected power flow over a much wider
area, up through New York and into New England.
As for your ideas about 'phase-locked loop', well, let's just say you
haven't taken any power transmission courses or operated any transmission
lines, have you?
daestrom
| |
|
| On Feb 14, 4:55 pm, "Don Kelly" <d...@shaw.ca> wrote:
> As for the synchroscope- a set of lights works well. Three sets of 240V
> lamps (for 120V systems) connected directly across the breaker, phase a to a
> etc will be all bright when out of phase and all dark when in phase and
> Increasing the input power shifts the phase of the machine and this
> increases the power output (and does affect speed but this won't normally
> be seen if the machine is small with respect to the system) How do you think
> that you correct frequency?
We don't. Frequency is decided by the system once you are
paralleled...you can't be out of phase with the system or of a
different frequency which is based on speed, not torque. You can
increase voltage or lower it via voltage regulation.
> It does NOT increase the DC field (an increase in field -through attempts
> to raise voltage, will increase reactive output from that machine).
You are correct...but total amps through the stator winding are a
function of the total generation.
> Oh, yes, there are no AC ties from Hudson's Bay to Baja California. Such
> ties would be unstable. Even between Alberta (tied to the Northwest power
> pool) and Saskatchewan (tied to the Midwest system) there are no AC links.
> There are DC, asynchronous links in this case and also a DC backbone link in
> the NW system which makes it possible to maintain the links from Western
> Canada through to the Baja.
Yeah, true, also between the Western States and Texas/Midwest, I think
in Missouri...a DC link flattens the phase angels, then retunes up
through inverters. But in effect, one can supply WATTS from Hudson Bay
to Baja, *through* the various DC-inter ties. I mention Baja because
they are actually part of the California power pool.
David Walters
| |
|
| On Feb 14, 6:58 pm, "operator jay" <n...@none.none> wrote:
> "Don Kelly" <d...@shaw.ca> wrote in message
>
> news:lcOAh.985903$5R2.936881@pd7urf3no...
>
>
> Interesting. I never knew that. I found these. (They get a little
> repetitive).http://en.wikipedia.org/wiki/Image:...org/wiki/Texas_
Interconnectionhttp://en.wikipedia.org/wiki/Alaska_Interconnection
> In a typical day what is the (peak) combined MW being transmitted over
> these dc links? A tiny percentage of all the power being consumed?
| |
|
| On Feb 14, 7:20 pm, "daestrom" <daestrom@NO_SPAM_HEREtwcny.rr.com>
wrote:
>
>
> So sayeth someone that has probably never brought a generator on-line.
>
> The 'grid' is what it is. A major network of interconnected generation and
> load stations. There are actually several 'sections' that are *not*
> synchronized, such as the west to east and Texas has it's own 'grid'.
> Nevertheless, there are interconnecting points with DC links to allow power
> to flow between sections.
>
> A major part of the reason for the blackout in 2003 was 'grid' disturbances
> in Ohio, lower Michigan, and Ontario affected power flow over a much wider
> area, up through New York and into New England.
>
> As for your ideas about 'phase-locked loop', well, let's just say you
> haven't taken any power transmission courses or operated any transmission
> lines, have you?
>
> daestrom
100% correct. "There is no grid"!! A huh. What is it I parallel my gas
turbines to everyday? My hot-tub?
David
| |
| zzbunker@netscape.net 2007-02-15, 3:25 am |
| On Feb 14, 10:15 pm, "Don Kelly" <d...@shaw.ca> wrote:
> ----------------------------<zzbun...@netscape.net> wrote in message
>
> news:1171495225.571670.275450@h3g2000cwc.googlegroups.com...
>
>
>
>
> ---------
> Unfortunately, in phase locking a generator to a system which consists of a
> "grid" (which is not a fiction) the result is that the output of the
> generator will be 0.
It is 100% pure fiction, since the only
thing morons with 1000 MW generators
are coupled to is four foot roller bearings
and Enron retards
than can mumble "grid" in four New Dork languages.
>
> Do not try to apply electronic ideas to a power grid which involves both
> mechanical and electrical . They very often , at best, don't work.
> Also considering the number of independent variables and non-linearities
> involved, electronic systems, including computers, are relatively trivial
> and uncomplicated.
>
> Phase locking is the ideal in smoothly synchronising a generator to the grid
> BUT once the machine is "on line" it is neither beneficial nor wanted.
> Shifting the phase of a generator with regard to the other generators on the
> system is necessary for production of power from that generator. Of course
> the dynamics of the electrical system and the mechanical systems involved
> are factors.
>
> Another case is maximum power transfer:
> Maximum power transfer is not a desirable operating strategy from an
> efficiency viewpoint or from a stability viewpoint. Not only will it not be
> efficient, it would not be a possible operating regime.
>
> --
>
> Don Kelly d...@shawcross.ca
> remove the X to answer
| |
| Don Kelly 2007-02-15, 3:25 am |
| ----------------------------
"operator jay" <none@none.none> wrote in message
news:S%PAh.1045$gT4.307@newsfe18.lga...
>
> "Don Kelly" <dhky@shaw.ca> wrote in message
> news:lcOAh.985903$5R2.936881@pd7urf3no...
>
>
>
> Interesting. I never knew that. I found these. (They get a little
> repetitive).
> http://en.wikipedia.org/wiki/Image:Nercmap.JPG
> http://en.wikipedia.org/wiki/Western_Interconnection
> http://en.wikipedia.org/wiki/Eastern_Interconnection
> http://en.wikipedia.org/wiki/Qu%C3%...Interconnection
> http://en.wikipedia.org/wiki/Texas_Interconnection
> http://en.wikipedia.org/wiki/Alaska_Interconnection
> In a typical day what is the (peak) combined MW being transmitted over
> these dc links? A tiny percentage of all the power being consumed?
>
--------------
Not necessarily a tiny part of the total load when you consider lines
capable of transferring 3000MW. The energy from Northern Manitoba to the
south is all through DC links (see Nelson River and/or Manitoba Hydro ).
Much (probably most) of what is exported south from Quebec is through
DClinks. The internal link in the NW power pool does have appreciable
capacity- it wouldn't actually be worth while if it didn't.
As to the actual peak transfer through these lines - I don't know that.
There are some links which are small potatoes such as the
Alberta-Saskatchewan link which is between two of the regions listed in your
first reference. Can these be stronger? Certainly but not with AC links.
There are two main reasons for long distance DC transmission. (a)
elimination of problems with AC transmission due to long lines provided by
an asynchronous tie. (b) Economics.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
| |
| Don Kelly 2007-02-15, 3:25 am |
|
"nada" <dwaltersMIA@gmail.com> wrote in message
news:1171509682.431182.287370@a34g2000cwb.googlegroups.com...
> On Feb 14, 4:55 pm, "Don Kelly" <d...@shaw.ca> wrote:
>
>
> We don't. Frequency is decided by the system once you are
> paralleled...you can't be out of phase with the system or of a
> different frequency which is based on speed, not torque. You can
> increase voltage or lower it via voltage regulation.
----------
There is a bit more to it than that. Phase differences exist and must
exist. That doesn't mean a frequency difference. If you are in phase with
the grid and at the same voltage- you deliver neither power or reactive. If
you try to speed up an individual generator, you actually do speed up the
system a bit but mainly you advance in phase which leads to more power
delivered to the system. The actual frequency is dependent on the governor
droop settings and the share of the load taken by a given machine. Another
control, (load frequency) system wide is used to control the frequency of
the system as a whole by adjusting all the prime movers as desired. This
will include changing of load sharing between machines.
As to voltage control, an adjustment which can make a big difference in
voltage for an isolated machine, will have a much smaller effect on a
machine connected to the system because its main effect is to change VAR
production from that machine.
For example, a generator tied to an "infinite bus" which is a grid which is
much larger than the generator- admittedly ideal limiting case- the voltage
and frequency is fixed. Any attempt to speed up increases power output. Any
attempt to increase voltage results in more Var output. In this limiting
case the frequency and voltage do not change. In practice, depending on the
relative size of the generator and the strength of its ties to the grid-
some voltage and frequency changes do occur.
>
>
> You are correct...but total amps through the stator winding are a
> function of the total generation.
------
A function of the KVA not KW.
--------------------
>
>
> Yeah, true, also between the Western States and Texas/Midwest, I think
> in Missouri...a DC link flattens the phase angels, then retunes up
> through inverters. But in effect, one can supply WATTS from Hudson Bay
> to Baja, *through* the various DC-inter ties. I mention Baja because
> they are actually part of the California power pool.
-----
DC links are possible but they don't "flatten the phase angles". In theory
one can deliver power from Hudson's Bay to Baja through DC links. However,
do these links actually exist or, for those that do, (such as the
Alberta-Saskatchewan link) are they significant except on a local basis? I
expect that, in the future such ties will be there leading to what may end
up as a continent wide interconnection. Certainly the Manitoba south links
and the Quebec south links are significant and the internal link in the
Northwest power pool is significant as a backbone to that system.
In any case, DC links do not control frequency at either end. They inject or
suck MW and suck MVARs.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
| |
| Eeyore 2007-02-15, 9:25 am |
|
lekosmoth@yahoo.com wrote:
> Hi,
>
> I am trying to learn more about synchronizing a mini power station to
> a national grid network.
What is there to learn ?
Graham
| |
| dave.walters@comcast.net 2007-02-15, 9:25 am |
| On Feb 14, 7:56 pm, zzbun...@netscape.net wrote:
>
> It is 100% pure fiction, since the only
> thing morons with 1000 MW generators
> are coupled to is four foot roller bearings
> and Enron retards
> than can mumble "grid" in four New Dork languages.
So...when *you* plug your toaster into the wall socket, you are
drawing power from what exactly????
David
| |
| dave.walters@comcast.net 2007-02-15, 9:25 am |
| On Feb 14, 4:55 pm, "Don Kelly" <d...@shaw.ca> wrote:
>
> Increasing the input power shifts the phase of the machine and this
> increases the power output (and does affect speed but this won't normally
> be seen if the machine is small with respect to the system) How do you think
> that you correct frequency?
> It does NOT increase the DC field (an increase in field -through attempts
> to raise voltage, will increase reactive output from that machine).
Yes, but it starts with the torque developed by more motive force
(steam/water) into a turbine. The torque is delivered by the shaft to
the generator. You can't shift the phase of the machine without
increased torque.
David
| |
| Don Kelly 2007-02-15, 9:25 pm |
| <zzbunker@netscape.net> wrote in message
news:1171511815.177283.101490@v45g2000cwv.googlegroups.com...
> On Feb 14, 10:15 pm, "Don Kelly" <d...@shaw.ca> wrote:
>
> It is 100% pure fiction, since the only
> thing morons with 1000 MW generators
> are coupled to is four foot roller bearings
> and Enron retards
> than can mumble "grid" in four New Dork languages.
>
------------------
There are many good technical and economic reasons for a "grid"
interconnection.
You mention blackouts but consider this- the overall reliability of the grid
is well above that of any electronic system in existence and the
interconnections aid this.
That doesn't mean that MBA's in charge of some utilities know any more than
you do about this and practice short term, short sighted policies. Their
ignorance is just as great as yours. That is the problem.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
| |
| Don Kelly 2007-02-15, 9:25 pm |
| <dave.walters@comcast.net> wrote in message
news:1171546431.590245.263870@v33g2000cwv.googlegroups.com...
> On Feb 14, 4:55 pm, "Don Kelly" <d...@shaw.ca> wrote:
>
>
> Yes, but it starts with the torque developed by more motive force
> (steam/water) into a turbine. The torque is delivered by the shaft to
> the generator. You can't shift the phase of the machine without
> increased torque.
---------
Agreed and I have not said anything to the contrary. I did say power input
but as speed is essentially constant, that translates to an increase in
torque. There is then a counter torque produced by the electrical system,
which is mainly dependent on phase, and a new balance will be reached at
nearly the same speed , increased power angle and higher power output The
whole system will be at a slightly higher speed - say an increase from 60 to
60.01 Hz and other generation will have lost some load equivalent to the
load picked up by the unit being controlled. This will have to be corrected
through an external control. If you have a good recording frequency meter
you will see the variations up and down that are always occurring as load
changes. Certainly the dynamics of the prime mover and the governor are part
of the picture. In particular, the governors of all prime movers have droop
(speed regulation) and do not try to maintain absolutely constant frequency.
This is necessary for proper load sharing between units. -
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
>
> David
>
| |
| zzbunker@netscape.net 2007-02-16, 9:25 am |
| On Feb 15, 9:54 pm, "Don Kelly" <d...@shaw.ca> wrote:
> <zzbun...@netscape.net> wrote in message
>
> news:1171511815.177283.101490@v45g2000cwv.googlegroups.com...
>
>
>
>
>
>
>
>
> ------------------
> There are many good technical and economic reasons for a "grid"
> interconnection.
Of course there are,
But the economic problem with power grids, is that they all
only concern GE and Westinghouse
and no other corporations,
> You mention blackouts but consider this- the overall reliability of the grid
> is well above that of any electronic system in existence and the
> interconnections aid this.
> That doesn't mean that MBA's in charge of some utilities know any more than
> you do about this and practice short term, short sighted policies. Their
> ignorance is just as great as yours. That is the problem.
>
> --
>
> Don Kelly d...@shawcross.ca
> remove the X to answer
> ----------------------------
| |
| zzbunker@netscape.net 2007-02-16, 1:25 pm |
| On Feb 15, 7:57 am, dave.walt...@comcast.net wrote:
> On Feb 14, 7:56 pm, zzbun...@netscape.net wrote:
>
>
> So...when *you* plug your toaster into the wall socket, you are
> drawing power from what exactly????
From Corning.
Since GE is too stupid to make toasters
that work in anything other than
moron Boeing 10g fields,
And Black&Decker is too pathetic
to make anything other than
7-11 pinups for Ford morons.
>
> David
| |
| Don Kelly 2007-02-16, 9:25 pm |
|
<zzbunker@netscape.net> wrote in message
news:1171636492.500825.67880@k78g2000cwa.googlegroups.com...
> On Feb 15, 9:54 pm, "Don Kelly" <d...@shaw.ca> wrote:
>
> Of course there are,
> But the economic problem with power grids, is that they all
> only concern GE and Westinghouse
> and no other corporations,
>
--------------
This is blatently false and based on personal bias which is not backed by
facts.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
------------
>
| |
| zzbunker@netscape.net 2007-02-17, 3:25 am |
| On Feb 16, 10:22 pm, "Don Kelly" <d...@shaw.ca> wrote:
> <zzbun...@netscape.net> wrote in message
>
> news:1171636492.500825.67880@k78g2000cwa.googlegroups.com...
>
>
>
>
>
>
>
>
>
>
>
>
> --------------
> This is blatently false and based on personal bias which is not backed by
> facts.
Well it has to true, since the only other bullshit facts morons like
Washington could possibly throw into
the power grid requation at this point in space-time is
that Jane Fonda runs the electric power grid.
> --
>
> Don Kelly d...@shawcross.ca
> remove the X to answer
> ----------------------------
> ------------
>
>
| |
| Michael Moroney 2007-02-17, 5:25 pm |
| dave.walters@comcast.net writes:
>In order to "parallel" the 3 phases, each A-B-C phase for your power
>source (wheather it's 100 watts or 1,000 megawatts, it makes no
>difference) has to be in "syncronization" with A-B-C phases of the
>system, which all work in harmony, from Hudson bay to northern Baja
>California.
>In large units, we do this manually (and now, automically) by using
>what's called a 'synch' scope with a rotating arm (representing the
>phase angle of the 3 phases as one, in relationship to the phase
>angles of the sytsem. When they are at "unity", that is the arrow on
>the meter facing straight up, we close the paralleling breaker. When
>this happens the system "grabs", quite literaly, our generator and the
>3 phase angles move in harmony/synchronization. The 'speed' of the
>turbine/generator, wheter 1800 RPMs or 3600 RPMs is then forced driven
>by the system and not your primary energy source (steam). No matter
>how much more steam (or water as in hydro) you add, the speed with
>always stay the same. Which is how power is increased because the
>steam, while not adding speed, adds torque, which, by increasing the
>DC field, increases megawatts.
Since the synchronization will never be perfect, there must still be a
substantial surge/mechanical force/BANG at the point the relays close,
particularly for the largest generators. Does this cause wear and tear
such that components have to be repaired after a certain number of times
of bringing the generator online? How large are the largest individual
generators, anyway. I know the largest power plants don't put all their
power through a single generator.
Speaking of BANG, I heard a description of the first time the St Lawrence
Seaway hydropower system (a few thousand MW total) was first brought
online, some time around 1960. Supposedly the HV transmission lines
themselves went BANG, because the individual wire strands in the cable
were attracted to each other when they first carried current. Do HV
transmission lines do that (bang) when first placed into service?
| |
| Don Kelly 2007-02-17, 9:25 pm |
| "Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
news:er7vam$604$1@pcls6.std.com...
> dave.walters@comcast.net writes:
>
>
>
> Since the synchronization will never be perfect, there must still be a
> substantial surge/mechanical force/BANG at the point the relays close,
> particularly for the largest generators. Does this cause wear and tear
> such that components have to be repaired after a certain number of times
> of bringing the generator online? How large are the largest individual
> generators, anyway. I know the largest power plants don't put all their
> power through a single generator.
>
> Speaking of BANG, I heard a description of the first time the St Lawrence
> Seaway hydropower system (a few thousand MW total) was first brought
> online, some time around 1960. Supposedly the HV transmission lines
> themselves went BANG, because the individual wire strands in the cable
> were attracted to each other when they first carried current. Do HV
> transmission lines do that (bang) when first placed into service?
---------
With even manual synchronisation, the process can be very smooth. Automatic
synchronisers may dither around awhile but also provide reliable and smooth
synchronisation. Substantial surges can be easily avoided unless stupidity
is at play.
As for generator sizes- hydro units in the 500MVA range and thermal units up
to 1000-1200MVA are in use. Generally there are multiple units in a plant-
economics and the need to not put all one's eggs in one basket determine
this.
As for the lines going bang- very questionable. The forces between phases
won't do it. However, with bundled conductors (multiple conductors in
parallel-spaced about a foot apart) , forces between conductors in the same
bundle will be attractive and can pull the conductors together. This has
happened under fault conditions but it is doubtful under load. Spacers are
used to maintain the separation and many are spring loaded so that they give
a bit under high forces and then recover the spacing (this is easier on the
conductors).
Don Kelly
dhky@shawcross.ca
remove the X to answer
----------------------------
| |
| Don Kelly 2007-02-18, 3:25 am |
| <zzbunker@netscape.net> wrote in message
news:1171689000.052923.246520@t69g2000cwt.googlegroups.com...
> On Feb 16, 10:22 pm, "Don Kelly" <d...@shaw.ca> wrote:
>
> Well it has to true, since the only other bullshit facts morons like
> Washington could possibly throw into
> the power grid requation at this point in space-time is
> that Jane Fonda runs the electric power grid.
>
-----------------------------
Ah, yes, don't try to find out the facts- they might not fit your favourite
misconceptions.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
| |
| Michael Moroney 2007-02-18, 3:25 am |
| "Don Kelly" <dhky@shaw.ca> writes:
>"Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
>news:er7vam$604$1@pcls6.std.com...
>---------
>With even manual synchronisation, the process can be very smooth. Automatic
>synchronisers may dither around awhile but also provide reliable and smooth
>synchronisation. Substantial surges can be easily avoided unless stupidity
>is at play.
OK. I just imagined that if you had a generator spinning at a rate such
that it would generate 60.01 Hz being synched to a 60.00 grid, even if
you switched exactly in phase, the grid would demand the thing spin at
exactly the right rate and even with a small difference, that's a lot of
decelleration or acceleration in a very short time, and with something
very massive.
>As for generator sizes- hydro units in the 500MVA range and thermal units up
>to 1000-1200MVA are in use. Generally there are multiple units in a plant-
>economics and the need to not put all one's eggs in one basket determine
>this.
Yes I figured the eggs-in-one-basket would be a major factor.
>As for the lines going bang- very questionable. The forces between phases
>won't do it. However, with bundled conductors (multiple conductors in
>parallel-spaced about a foot apart) , forces between conductors in the same
>bundle will be attractive and can pull the conductors together. This has
>happened under fault conditions but it is doubtful under load. Spacers are
>used to maintain the separation and many are spring loaded so that they give
>a bit under high forces and then recover the spacing (this is easier on the
>conductors).
I wasn't thinking of between phases or bundled conductors, I was thinking
of individual wires in a single cable (the big 'wire'). Often such cables
have 7 or 19 individual strands, and I believe the ones for transmission
lines are aluminum except the center one is steel for strength.
Substantial current in parallel conductors (the individual strands) in the
same direction attracts the strands magnetically, and supposedly the
cables magnetically constricted with a bang as the strands were attracted
to each other. I suppose at the voltages involved the strands may be
repelled from each other by the charge.
FWIW, the towers in the immediate area are the metal lattice towers with
6 single conductors, none seem to be bundled conductors with spacers.
It's a forest of those towers there.
| |
| Tzortzakakis Dimitrios 2007-02-18, 1:25 pm |
|
Ο "Michael Moroney" <moroney@world.std.spaamtrap.com> έγραψε στο μήνυμα
news:er7vam$604$1@pcls6.std.com...
> dave.walters@comcast.net writes:
>
>
>
> Since the synchronization will never be perfect, there must still be a
> substantial surge/mechanical force/BANG at the point the relays close,
> particularly for the largest generators. Does this cause wear and tear
> such that components have to be repaired after a certain number of times
> of bringing the generator online? How large are the largest individual
> generators, anyway. I know the largest power plants don't put all their
> power through a single generator.
>
No, they do (at least in EU).The new EURATOM reactor nuclear plant has as
much as 2000 MVA "on one shaft".It's some very advanced nuclear technology,
very safe and robust.What must really be redundant, is the cooling system
exchanger for the reactor, from which there are 4, and the backup cooling
system.(See under www.areva.com for more info).
> Speaking of BANG, I heard a description of the first time the St Lawrence
> Seaway hydropower system (a few thousand MW total) was first brought
> online, some time around 1960. Supposedly the HV transmission lines
> themselves went BANG, because the individual wire strands in the cable
> were attracted to each other when they first carried current. Do HV
> transmission lines do that (bang) when first placed into service?
No, but here in Crete we had one incident where an 150 kV insulator was
shorted, and the result was a brownout.I know that for sure the fuses of MV
(>= 15 kV) grids must handle 250 MVA of impulse short circuit apparent
power, so on 150 kV HV transmission that must be even larger.
--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
dimtzort AT otenet DOT gr
| |
| Don Kelly 2007-02-18, 8:25 pm |
|
"Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
news:er8o4q$o24$1@pcls6.std.com...
> "Don Kelly" <dhky@shaw.ca> writes:
>
>
> OK. I just imagined that if you had a generator spinning at a rate such
> that it would generate 60.01 Hz being synched to a 60.00 grid, even if
> you switched exactly in phase, the grid would demand the thing spin at
> exactly the right rate and even with a small difference, that's a lot of
> decelleration or acceleration in a very short time, and with something
> very massive.
------------
Your thinking is right and in the scenario the incoming machine would be
decelerated and during this time, it would pick up load. At the same time
the system would speed up somewhat. If the "droop" or speed regulation of
the governor was a typical 5% the load picked up in the above case would be
about 0.02% of the machine's rating. How long it would take to decellerate
would depend on the intertia of the machine. I doublt whether one, standing
by the machine would notice the "bump" Now at 61Hz- you would definitely
notice.
-----------
>
>
> Yes I figured the eggs-in-one-basket would be a major factor.
>
>
> I wasn't thinking of between phases or bundled conductors, I was thinking
> of individual wires in a single cable (the big 'wire'). Often such cables
> have 7 or 19 individual strands, and I believe the ones for transmission
> lines are aluminum except the center one is steel for strength.
> Substantial current in parallel conductors (the individual strands) in the
> same direction attracts the strands magnetically, and supposedly the
> cables magnetically constricted with a bang as the strands were attracted
> to each other. I suppose at the voltages involved the strands may be
> repelled from each other by the charge.
-------
First of all, the ACSR cables have individual wires in contact with each
other. A typical (smallish)conductor may have 26 aluminum conductors over 7
steel conductors and larger conductors will have more layers of each (7
strand is the smallest and not used for HV transmission). Yes there will be
some constriction but this will not cause a "bang" as they are already in
close contact- some squeeze- true- but the worst squeeze would be under
fault conditions.
There will be no repulsion due to charges as all these conductors are at the
same voltage.
------------
>
> FWIW, the towers in the immediate area are the metal lattice towers with
> 6 single conductors, none seem to be bundled conductors with spacers.
> It's a forest of those towers there.
-------
These would be 2 -3 phase circuits on the same tower and some would be older
lines. Many lines at 240KV or lower are not bundled. At higher voltages,
bundling is used for its advantages of lower weight of conductor, lower
electric fields in the vicinity of the conductors, lower line inductance and
easier installation -hence economic and electrical/mechanical advantages. It
is a way to effectively approximate a large diameter single conductor (e.g.
2-0.25 inch radius conductors, spaced 12 inches apart will have an
equivalent electrical radius of about 1.7 inches but a fraction(4%) of the
weight or cost of an equivalent (solid)single conductor.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
| |
| Bill Ghrist 2007-02-19, 3:25 am |
| In-Reply-To: <ti6Ch.1045774$R63.709738@pd7urf1no>
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Date: Mon, 19 Feb 2007 05:31:11 GMT
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Xref: number1.nntp.dca.giganews.com alt.engineering.electrical:186933 sci.energy:178616
Don Kelly wrote:
> "Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
> news:er8o4q$o24$1@pcls6.std.com...
> ------------
> Your thinking is right and in the scenario the incoming machine would be
> decelerated and during this time, it would pick up load. At the same time
> the system would speed up somewhat. If the "droop" or speed regulation of
> the governor was a typical 5% the load picked up in the above case would be
> about 0.02% of the machine's rating. How long it would take to decellerate
> would depend on the intertia of the machine. I doublt whether one, standing
> by the machine would notice the "bump" Now at 61Hz- you would definitely
> notice.
> -----------
Actually, synchronization is usually performed with the generator
frequency (speed) slightly higher than the grid frequency, just to make
sure that it comes on line with positive, not negative loading. The
load is then immediately raised (generally to about 5%, if I remember
correctly). The grid frequency, and consequently the speed of the
turbine generator, randomly fluctuates by the sort of magnitude that you
are talking about (0.01 Hz) or more (a good deal more in small grids,
such as on an island like Taiwan, for example). This is because of the
constant step changes in system demand from large loads being switched
on and off. The turbine generators are quite capable of changing speed
by that much in very short times (fractions of a second); they do it all
the time. Standard speeds, by the way, for steam turbine generators at
60 Hz are 3600 rpm for fossil units and 1800 rpm for nuclear units.
Bill Ghrist
| |
|
| On Wed, 14 Feb 2007 22:20:11 -0500, "daestrom"
<daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:
>The 'grid' is what it is. A major network of interconnected generation and
>load stations. There are actually several 'sections' that are *not*
>synchronized, such as the west to east and Texas has it's own 'grid'.
>Nevertheless, there are interconnecting points with DC links to allow power
>to flow between sections.
What is the location (terminal points) of the various DC lines that
provide inter-regional connections?
| |
| Ben Gustave 2007-02-20, 8:25 pm |
| "BobT" <fake@invalid.net> wrote in message
news:g2ajt2pigfckukeb6k3ha5un1lamu75hbd@4ax.com...
> On Wed, 14 Feb 2007 22:20:11 -0500, "daestrom"
> <daestrom@NO_SPAM_HEREtwcny.rr.com> wrote:
...
> What is the location (terminal points) of the various DC lines that
> provide inter-regional connections?
Check out this link:
http://eceserv0.ece.wisc.edu/~dobso...sicistNov03.pdf
| |
| Don Kelly 2007-02-20, 9:25 pm |
| "Ben Gustave" <bengustave@shawREMOVE.ca> wrote in message
news:9FNCh.1079697$R63.447569@pd7urf1no...
> "BobT" <fake@invalid.net> wrote in message
> news:g2ajt2pigfckukeb6k3ha5un1lamu75hbd@4ax.com...
> ...
>
> Check out this link:
> http://eceserv0.ece.wisc.edu/~dobso...sicistNov03.pdf
>
This is an excellent link. It does point out one of the problems of the
"bottom line, now" philosophy(sic) behind deregulation that is a favourite
XXXXX of mine. There is one questionable statement but, in context, it is
trivial and doesn't detract from the thrust of the article.
Thank you,
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
| |
|
| In the REAL World, syncronization is simply not a problem, nor has it
ever been one. "Wires getting attracted to each other" is ridiculous,
this could only occur if one had opposite graveling voltage, which it
doesn't.
Big nuclear plants only have to parallel once every fuel cycle (like
every 18months to 2 years) and other plants paralleling the unit's is
a piece of cake. this shouldn't even be a discussion as it is not a
discussion among power plant operators or grid operators.
Wit the grid, when a large loss of gerneration occurs...like when PG&E
was testing a dual-full load trip/paralleling breaker opening with the
instant loss of 2400 MWs...that is when you feel it. I was on the day
they tested this and it seem that our 210 MW generator almost jumped
off it's pedestal! Every generator in the system had to instantly make
up for loss of 2400 megawatts which meant the steam governor valves
(which respond to "speed of the system" immediately opened up to allow
for more power. Fun times...
David
>
>
> Actually, synchronization is usually performed with the generator
> frequency (speed) slightly higher than the grid frequency, just to make
> sure that it comes on line with positive, not negative loading. The
> load is then immediately raised (generally to about 5%, if I remember
> correctly). The grid frequency, and consequently the speed of the
> turbine generator, randomly fluctuates by the sort of magnitude that you
> are talking about (0.01 Hz) or more (a good deal more in small grids,
> such as on an island like Taiwan, for example). This is because of the
> constant step changes in system demand from large loads being switched
> on and off. The turbine generators are quite capable of changing speed
> by that much in very short times (fractions of a second); they do it all
> the time. Standard speeds, by the way, for steam turbine generators at
> 60 Hz are 3600 rpm for fossil units and 1800 rpm for nuclear units.
>
> Bill Ghrist
| |
| Tzortzakakis Dimitrios 2007-02-21, 5:25 pm |
|
? "Bill Ghrist" <notmyname@notmyisp.com> ?????? ??? ??????
news:zCaCh.723$CG5.562@trnddc03...
> Don Kelly wrote:
cable[color=darkred]
stupidity[color=darkred]
such[color=darkred]
of[color=darkred]
time[color=darkred]
of[color=darkred]
be[color=darkred]
decellerate[color=darkred]
standing[color=darkred]
>
> Actually, synchronization is usually performed with the generator
> frequency (speed) slightly higher than the grid frequency, just to make
> sure that it comes on line with positive, not negative loading. The
> load is then immediately raised (generally to about 5%, if I remember
> correctly).
What about the wind-turbines (or generators)?How they are paralleled?How it
is assured that they have positive loading?There is *no* way to increase the
wind speed at will, like you do with steam or water.How do they pick up
loads?Is it a bit of snake oil, aka Enron?
--
Tzortzakakis Dimitrios
major in electrical engineering
mechanized infantry reservist
dimtzort AT otenet DOT gr
>The grid frequency, and consequently the speed of the
> turbine generator, randomly fluctuates by the sort of magnitude that you
> are talking about (0.01 Hz) or more (a good deal more in small grids,
> such as on an island like Taiwan, for example). This is because of the
> constant step changes in system demand from large loads being switched
> on and off. The turbine generators are quite capable of changing speed
> by that much in very short times (fractions of a second); they do it all
> the time. Standard speeds, by the way, for steam turbine generators at
> 60 Hz are 3600 rpm for fossil units and 1800 rpm for nuclear units.
>
> Bill Ghrist
| |
| Bill Ward 2007-02-21, 5:25 pm |
| On Wed, 21 Feb 2007 21:43:06 +0200, Tzortzakakis Dimitrios wrote:
<snip>
> What about the wind-turbines (or generators)? How they are
> paralleled? How it is assured that they have positive loading? There
> is *no* way to increase the wind speed at will, like you do with steam
> or water. How do they pick up loads? Is it a bit of snake oil, aka
> Enron?
Synchronous inverters.
Bill Ward
| |
| phil-news-nospam@ipal.net 2007-02-21, 5:25 pm |
| In alt.engineering.electrical nada <dwaltersMIA@gmail.com> wrote:
| Wit the grid, when a large loss of gerneration occurs...like when PG&E
| was testing a dual-full load trip/paralleling breaker opening with the
| instant loss of 2400 MWs...that is when you feel it. I was on the day
| they tested this and it seem that our 210 MW generator almost jumped
| off it's pedestal! Every generator in the system had to instantly make
| up for loss of 2400 megawatts which meant the steam governor valves
| (which respond to "speed of the system" immediately opened up to allow
| for more power. Fun times...
I wonder how their generator(s) reacted to that (sudden loss of load).
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-02-21-1641@ipal.net |
|------------------------------------/-------------------------------------|
| |
|
| On Feb 21, 2:42 pm, phil-news-nos...@ipal.net wrote:
> In alt.engineering.electrical nada <dwalters...@gmail.com> wrote:
>
> | Wit the grid, when a large loss of gerneration occurs...like when PG&E
> | was testing a dual-full load trip/paralleling breaker opening with the
> | instant loss of 2400 MWs...that is when you feel it. I was on the day
> | they tested this and it seem that our 210 MW generator almost jumped
> | off it's pedestal! Every generator in the system had to instantly make
> | up for loss of 2400 megawatts which meant the steam governor valves
> | (which respond to "speed of the system" immediately opened up to allow
> | for more power. Fun times...
>
> I wonder how their generator(s) reacted to that (sudden loss of load).
I don't know. I suspect because they are DC, at least they were back
then, they were able to absorb the lost of generation. BTW...Load is
the demand, Generation is they supply. We lost generation, not load,
thus voltage was dragged down in the entire system.
David
| |
| Don Kelly 2007-02-22, 3:25 am |
|
"nada" <dwaltersMIA@gmail.com> wrote in message
news:1172082737.572264.71330@l53g2000cwa.googlegroups.com...
> In the REAL World, syncronization is simply not a problem, nor has it
> ever been one. "Wires getting attracted to each other" is ridiculous,
> this could only occur if one had opposite graveling voltage, which it
> doesn't.
-----------
Excuse me. Forces between conductors depend on the currents, not the
voltage. These forces exist- and will be attractive or repulsive depending
on whether the currents are in the same or opposite directions. In the REAL
world there are many situations in machines, high current bus bars,
transformers, and between parallel conductors in a bundle -hence the needs
for spacers and or physical bracing of windings to withstand forces due to
fault currents.
------------
>
> Big nuclear plants only have to parallel once every fuel cycle (like
> every 18months to 2 years) and other plants paralleling the unit's is
> a piece of cake. this shouldn't even be a discussion as it is not a
> discussion among power plant operators or grid operators.
---------
You are right -it is not a problem as either operators are taught how to do
it, or, in the present day, it is done automatically. If it is not done
properly, it can be a big problem -hence the automatic controls. Aren't you
lucky
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
>
> Wit the grid, when a large loss of gerneration occurs...like when PG&E
> was testing a dual-full load trip/paralleling breaker opening with the
> instant loss of 2400 MWs...that is when you feel it. I was on the day
> they tested this and it seem that our 210 MW generator almost jumped
> off it's pedestal! Every generator in the system had to instantly make
> up for loss of 2400 megawatts which meant the steam governor valves
> (which respond to "speed of the system" immediately opened up to allow
> for more power. Fun times...
>
> David
>
>
>
| |
| Don Kelly 2007-02-22, 3:25 am |
| "nada" <dwaltersMIA@gmail.com> wrote in message
news:1172101547.912087.303450@m58g2000cwm.googlegroups.com...
> On Feb 21, 2:42 pm, phil-news-nos...@ipal.net wrote:
>
> I don't know. I suspect because they are DC, at least they were back
> then, they were able to absorb the lost of generation. BTW...Load is
> the demand, Generation is they supply. We lost generation, not load,
> thus voltage was dragged down in the entire system.
>
> David
>
---------
DC??? Since when since Edison's time has any utility system had DC
generators? Particularly ones in the multimegawatt range. DC transmission
lines- true but that doesn't change the problem with generators which has a
lot to do with the mechanical behaviour of the prime movers.
--
Don Kelly dhky@shawcross.ca
remove the X to answer
----------------------------
| |
| Matthew Beasley 2007-02-22, 1:25 pm |
|
"Tzortzakakis Dimitrios" <nowhere@noone.com> wrote in message
news:eri7g0$mrt$1@mouse.otenet.gr...
> What about the wind-turbines (or generators)?How they are paralleled?How
> it
> is assured that they have positive loading?There is *no* way to increase
> the
> wind speed at will, like you do with steam or water.How do they pick up
> loads?Is it a bit of snake oil, aka Enron?
Wind turbines do not start unless the wind speed is sufficient to produce
net generation.
As Bill Ward notes in the first reply to you, many wind turbines use an
inverter to tie to the grid. Where the wind speed is fairly constant,
induction generators may be used instead. The inverter units allow the
rotor speed to change to match wind speed, resulting in higher efficiency
above and below the design wind speed. But the inverter adds loss to the
system, so an inverter unit has lower efficiency at the design wind speed.
The induction generator wind turbines are more efficient at design wind
speed but are less efficient when the wind speed is off the design point.
The induction units are also less expensive.
An inverter wind turbine starts real nice. When the rotor is stopped, no
torque is generated because the airfoil is in a stall. When the wind speed
is high enough, the controller commands the inverter to start motoring the
rotor around until the rotor speed becomes high enough that the power flow
can be reversed and power is sent to the grid. Everything can be nice and
smooth - the generator is sending power to the grid shortly after the blades
come out of stall, so the approach to operating speed occurs slow.
Induction generator wind turbines do not start as elegantly. The units I
have seen use a SCR based low voltage starter. When the wind speed is high
enough to start, a low voltage(maybe 20% of nominal) is applied to the
induction generator. This will start the rotor spinning. Once the turbine
comes out of stall, the reduced voltage starter will be blanked off, cutting
the motoring torque. This is to help reduce the backlash banging as the
gearbox goes from motoring to generating torque - by having the turbine do
the final acceleration of the induction machine rotor, all of the backlash
will be taken up on the generating direction. As the induction machine
rotor goes through synchronous frequency the soft start is ramped up to full
voltage and then the SCRs are bypassed by a contactor. The rate limit on
the second application of voltage is usually based on limiting the maximum
kVAR load to the grid. The timing is very critical. If the line voltage is
applied early (before synchronous speed is reached), the induction machine
will motor then quickly swing to generation. When the torque reverses, a
terrible jolt hits because of the backlash of gearbox plus flex in the
tower, blades, and nacelle. If line voltage is applied late, the induction
machine will have accelerated beyond synchronous speed, and the jolt of
decelerating all of the rotating mass can be bad too. All of this is much
worse on an induction machine because they start at a much higher wind speed
than a variable speed unit would.
| |
| Matthew Beasley 2007-02-22, 1:25 pm |
|
"Michael Moroney" <moroney@world.std.spaamtrap.com> wrote in message
news:er7vam$604$1@pcls6.std.com...
> dave.walters@comcast.net writes:
> Since the synchronization will never be perfect, there must still be a
> substantial surge/mechanical force/BANG at the point the relays close,
> particularly for the largest generators.
If have been beside a 1250 MVAR unit when synchronized to the grid. No
discernable sound when it synchronized. The shafting was painted with black
and white stripes at one point, and under the discharge lighting in the
turbine bay, the difference speed prior to synchronization could easily be
observed. The shaft was rolling very slow above synchronous speed, and when
the breaker closed, the difference in speed stopped. As load is added, I
could easily see the phase angle shift a little.
What does make noise is when the phase angle shifts due to grid
disturbances. Being a fairly big machine there is some flex in the shaft
and it made funny noises, in combination with the sound GIANT steam valves
closing and re-opening trying to damp the oscillations.
A trip under load did bang, but that was the steam valves snapping shut plus
the breakers. The breakers were opened and closed using 450 PSI air. When
opening the breakers did make a pretty big retort, even though there was a
muffler. The cylinder was about 6" by about 3', so that's a LOT of air to
vent when charged to 450 PSI.
> Does this cause wear and tear
> such that components have to be repaired after a certain number of times
> of bringing the generator online?
The breakers would have PM after a certain number of cycles or years went
by. I believe that usually it was the time limit that expired. I don't
think the contacts were ever replaced, but that wasn't the area I worked in.
The responsibility for the HV breakers were under the substation maintenance
department of the company, far removed from plant operations.
> How large are the largest individual
> generators, anyway. I know the largest power plants don't put all their
> power through a single generator.
Figure 50 to 200 MW for gas turbine combined cycle plants.
Figure 300 to 750 MW for coal fired plants
Figure 600 to 1400 MW for nuke plants.
Hydro anywhere from the kW range to 600 MW
Wind turbine from the sub MW to 10MW, but most new in the 2-5 MW range.
>
> Speaking of BANG, I heard a description of the first time the St Lawrence
> Seaway hydropower system (a few thousand MW total) was first brought
> online, some time around 1960. Supposedly the HV transmission lines
> themselves went BANG, because the individual wire strands in the cable
> were attracted to each other when they first carried current. Do HV
> transmission lines do that (bang) when first placed into service?
I don't think they used grading resistors to cut the lines in and out at
first so it may have well banged because of the current inrush when the line
closed in. I have only once heard a 500kV line energize (the highest we
have on the west coast, at least for AC), and it had grading resistors to
energize the line. Lots of buzzing as the arms went by each resistor, but I
didn't hear any "bang" from the line.
| |
| Tzortzakakis Dimitrios 2007-02-28, 1:25 pm |
|
Ο <phil-news-nospam@ipal.net> έγραψε στο μήνυμα
news:erihs52bou@news1.newsguy.com...
> In alt.engineering.electrical nada <dwaltersMIA@gmail.com> wrote:
>
> | Wit the grid, when a large loss of gerneration occurs...like when PG&E
> | was testing a dual-full load trip/paralleling breaker opening with the
> | instant loss of 2400 MWs...that is when you feel it. I was on the day
> | they tested this and it seem that our 210 MW generator almost jumped
What is its fuel?In continental greece we use brown coal where this is
available-mazut or natural gas near the prime consumers' -that is mainly
Athens and in the least Thessaloniki.Installed power for cont. is around~8.5
GW, with lots of hydro, not larger than 125 MW each turb though (150 kV
transmission).There are 3 2-circuits 400 kV lines from the Kozani plateau to
Athens (Kozani-brown coal deposits,~1 billion tones left now).In islands
(LOTS of them and in Crete and Rhodes, primarily diesel engines, and in
Rhodes and Crete, base load units-> large diesels with mazut (up to 70,000
HP)small steam turbs (mazut) ->50 MW and small gas turbs->combined cycle
(one)125 MW open cycle->30 MW.Now, they plan to build one large station,in
Korakia, with I think, 2 *250 MW steam mazut fired units.
> | off it's pedestal! Every generator in the system had to instantly make
> | up for loss of 2400 megawatts which meant the steam governor valves
> | (which respond to "speed of the system" immediately opened up to allow
> | for more power. Fun times...
>
> I wonder how their generator(s) reacted to that (sudden loss of load).
>
> --
>
|---------------------------------------/----------------------------------|
> | Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below
|
> | first name lower case at ipal.net / spamtrap-2007-02-21-1641@ipal.net
|
>
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