[Milsurplus] Even Worse
Peter Gottlieb
nerd at verizon.net
Mon Jul 5 15:24:46 EDT 2010
All the dynamics of all the control systems across the grid can make for
an "interesting" day if something goes wrong.
Generally, most plants are looking to have a 1.0 PF at their point of
connection to the grid even if it takes significant reactive to get there.
(Yes, I know, gross oversimplification).
J. Forster wrote:
> By raising or lowering the field current, you can make the reactive power
> look capacitive or inductive respectively, but not instantaneously. The
> L/R time constant of the field circuit is nowhere near zero. The L is
> huge.
>
> -John
>
> ===============
>
>
>
>> Not the *source* but the reactive component can be changed
>> instantaneously if the path now goes through a large inductance.
>>
>> P
>>
>>
>>
>> J. Forster wrote:
>>
>>> Hi Peter,
>>>
>>> Clearly, power grids are not just wires, but must be treated as
>>> transmission lines. One wavelength of 60 Hz is about 3100 miles, so many
>>> power lines are a significant fraction of a WL long.
>>>
>>> However, my point is that you cannot change the phase of a source
>>> instantly with the flip of a switch. It takes seconds or tens of
>>> seconds,
>>> which makes control very hard.
>>>
>>> Any disturbances do not die out quickly either, complicating matters.
>>>
>>> -John
>>>
>>> ===============
>>>
>>>
>>>
>>>
>>>> This is not necessarily true. Long transmission lines are very
>>>> inductive, and dense cities (Boston, Detroit, NYC) with metal shielded
>>>> underground transmission lines can be quite capacitive. One real-life
>>>> situation that we modeled was the loss of a local feeder which caused
>>>> power flow through much longer transmission lines. This caused a step
>>>> change in reactive to higher inductance and was enough to de-stabilize
>>>> the system. These changes play out over seconds or tens of seconds,
>>>> surprisingly enough.
>>>>
>>>> As models get larger, due to limited computational power,
>>>> simplifications have to be made. There is a lot of work being done now
>>>> to make sure the simplifications made are correct!
>>>>
>>>> Peter
>>>>
>>>>
>>>> J. Forster wrote:
>>>>
>>>>
>>>>> The real issues in network stability are that, because of the large
>>>>> rotating inertias of generators, a rapid phase change is all but
>>>>> impossible. To change the phase of a machine with respect to the
>>>>> network,
>>>>> you have to speed it up a tad (more steam), let the phase change, and
>>>>> then
>>>>> slow it back down (less steam). This cannot be done quickly.
>>>>>
>>>>> Furthermore, in a simplified case, if you have just two AC generators
>>>>> connected together, the can "rock" against each other in phase
>>>>> (rocking
>>>>> is
>>>>> a variation of the relative phase of the rotors), and the rocking is
>>>>> very,
>>>>> very lightly damped. Extend this issue to a network with hundreds of
>>>>> machines and you have a giant mess.
>>>>>
>>>>> -John
>>>>>
>>>>> =================
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>> The real use of synchrophasors is not for power setting (that can
>>>>>> easily
>>>>>> be done by far less complex methods) but for early indication of grid
>>>>>> disturbances. This is getting more valuable as the control of the
>>>>>> grid
>>>>>> is moving to a model-based design. Humans just can't interpret and
>>>>>> respond fast enough to prevent cascading problems.
>>>>>>
>>>>>> Peter
>>>>>>
>>>>>>
>>>>>> J. Forster wrote:
>>>>>>
>>>>>>
>>>>>>
>>>>>>> Ah, yes. Phase shifting is easy in a polyphase system. For example,
>>>>>>> a
>>>>>>> Scott connected transformer can change 2 phase to 3 phase, or the
>>>>>>> inverse.
>>>>>>>
>>>>>>> Thanks,
>>>>>>>
>>>>>>> -John
>>>>>>>
>>>>>>> ==============
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>> Yes, it's done with a specialized tap-changing transformer called a
>>>>>>>> Phase
>>>>>>>> Angle Regulator. This paper describes how they're used:
>>>>>>>> http://www.npcc.org/viewDoc.aspx?name=Phase+Angle+Regulator+Operation+-May+2
>>>>>>>> 000.pdf&cat=LEER
>>>>>>>>
>>>>>>>> Albert
>>>>>>>>
>>>>>>>> -----Original Message-----
>>>>>>>> From: milsurplus-bounces at mailman.qth.net
>>>>>>>> [mailto:milsurplus-bounces at mailman.qth.net] On Behalf Of Larry
>>>>>>>> Godek
>>>>>>>> Sent: Sunday, July 04, 2010 6:10 PM
>>>>>>>> To: nerd at verizon.net; Milsurplus at mailman.qth.net
>>>>>>>> Subject: Re: [Milsurplus] Even Worse
>>>>>>>>
>>>>>>>> Do power companies share power back and forth according to peak
>>>>>>>> periods
>>>>>>>> by
>>>>>>>> changing the phase slightly? Where did i come up with this idea?
>>>>>>>> I
>>>>>>>> really
>>>>>>>> don't remember.
>>>>>>>>
>>>>>>>> Larry
>>>>>>>> W0OGH
>>>>>>>>
>>>>>>>>
>>>>>>>> --- On Sat, 7/3/10, Peter Gottlieb <nerd at verizon.net> wrote:
>>>>>>>>
>>>>>>>> From: Peter Gottlieb <nerd at verizon.net>
>>>>>>>> Subject: Re: [Milsurplus] Even Worse
>>>>>>>> To: jcoward5452 at aol.com
>>>>>>>> Cc: jfor at quik.com, milsurplus at mailman.qth.net
>>>>>>>> Date: Saturday, July 3, 2010, 1:46 PM
>>>>>>>>
>>>>>>>> The power companies already do that and is able to compare phasors
>>>>>>>> across the grid. Check out NASPI, the North American SynchroPhasor
>>>>>>>> Initiative.
>>>>>>>>
>>>>>>>> I set up a PMU (Phasor Measurement Unit) at my plant already, it
>>>>>>>> uses
>>>>>>>> GPS for time sync.
>>>>>>>>
>>>>>>>> Peter
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>> jcoward5452 at aol.com wrote:
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> Here at our secret development Lab, we phase lock the 60~ to a GPS
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>> receiver. This is how you make all the frequencies in the audio
>>>>>>>> spectrum
>>>>>>>> exact. This is really no secret as most Laboratories have a "house"
>>>>>>>> standard
>>>>>>>> derived from a GPS receiver.
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>> Jay
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> -----Original Message-----
>>>>>>>>> From: J. Forster <jfor at quik.com>
>>>>>>>>> To: Richard Brunner <brunneraa1p at comcast.net>
>>>>>>>>> Cc: milsurplus <milsurplus at mailman.qth.net>
>>>>>>>>> Sent: Sat, Jul 3, 2010 1:06 pm
>>>>>>>>> Subject: Re: [Milsurplus] Even Worse
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> There is a thread on another list about radioactive tubes. I
>>>>>>>>> replied:
>>>>>>>>> "And, isotopically pure Thorium likely costs $millions / pound.
>>>>>>>>> What an opportunity for the Audiophools! Now, your Tube Amp can be
>>>>>>>>> onstructed with eviro-pure tubes. No harmful radiation to
>>>>>>>>> contaminate
>>>>>>>>> the
>>>>>>>>> larity of the sound. We at, PT Barnam AudioLabs, use only
>>>>>>>>> isotopically
>>>>>>>>> ure Thorium cathodes!!"
>>>>>>>>> :-)))
>>>>>>>>> -John
>>>>>>>>> =============
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> This is beyond witless. Who are these people with so much money
>>>>>>>>> and
>>>>>>>>> so
>>>>>>>>> little sense? I notice they also can't spel, so it's
>>>>>>>>> consistent.
>>>>>>>>> Imagine, three brass spikes!
>>>>>>>>>
>>>>>>>>> Richard, AA1P
>>>>>>>>>
>>>>>>>>>
>>>>>>>>> On Sat, 2010-07-03 at 08:57 -0700, J. Forster wrote:
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>> http://www.cruzefirstaudio.com/tripoint.htm
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>>>
>>>>>>>>> _____________________________________________________________
>>>>>>>>> ilsurplus mailing list
>>>>>>>>> ome: http://mailman.qth.net/mailman/listinfo/milsurplus
>>>>>>>>> elp: http://mailman.qth.net/mmfaq.htm
>>>>>>>>> ost: mailto:Milsurplus at mailman.qth.net
>>>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>>>> lease help support this email list: http://www.qsl.net/donate.html
>>>>>>>>>
>>>>>>>>> ______________________________________________________________
>>>>>>>>> Milsurplus mailing list
>>>>>>>>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>>>>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>>>>> Post: mailto:Milsurplus at mailman.qth.net
>>>>>>>>>
>>>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>>>> Please help support this email list:
>>>>>>>>> http://www.qsl.net/donate.html
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>>>
>>>>>>>> ______________________________________________________________
>>>>>>>> Milsurplus mailing list
>>>>>>>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>>>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>>>> Post: mailto:Milsurplus at mailman.qth.net
>>>>>>>>
>>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>>> ______________________________________________________________
>>>>>>>> Milsurplus mailing list
>>>>>>>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>>>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>>>> Post: mailto:Milsurplus at mailman.qth.net
>>>>>>>>
>>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>>>
>>>>>>>> ______________________________________________________________
>>>>>>>> Milsurplus mailing list
>>>>>>>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>>>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>>>> Post: mailto:Milsurplus at mailman.qth.net
>>>>>>>>
>>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>>>
>>>>>>> ______________________________________________________________
>>>>>>> Milsurplus mailing list
>>>>>>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>>> Post: mailto:Milsurplus at mailman.qth.net
>>>>>>>
>>>>>>> This list hosted by: http://www.qsl.net
>>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> ______________________________________________________________
>>>>>> Milsurplus mailing list
>>>>>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>>>>>> Help: http://mailman.qth.net/mmfaq.htm
>>>>>> Post: mailto:Milsurplus at mailman.qth.net
>>>>>>
>>>>>> This list hosted by: http://www.qsl.net
>>>>>> Please help support this email list: http://www.qsl.net/donate.html
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>>
>>>>>
>>>>>
>>>
>>>
>>>
>> ______________________________________________________________
>> Milsurplus mailing list
>> Home: http://mailman.qth.net/mailman/listinfo/milsurplus
>> Help: http://mailman.qth.net/mmfaq.htm
>> Post: mailto:Milsurplus at mailman.qth.net
>>
>> This list hosted by: http://www.qsl.net
>> Please help support this email list: http://www.qsl.net/donate.html
>>
>>
>>
>
>
>
>
More information about the Milsurplus
mailing list