[Milsurplus] Even Worse

Mon Jul 5 14:46:44 EDT 2010

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
>>>
>>>
>>>
>>
>>
>>
>>
>
>