[Milsurplus] Even Worse

Mon Jul 5 14:53:54 EDT 2010

In fact, that's an ancestor of the EAI 680 analog computer I was using on
my graduate thesis in the early 1970s.

Analog computers are really neat toys, but they do require a deep
understanding of the problem to be useful. Otherwise GIGO.

-John

===================

> Sounds like you'd need a real computer (forget that Windows stuff) to
> figure
> it out:
> http://long-lines.net/other/electrical/ElectricalWorld-1955-12-12/009.html
>
> This is actually one of the smaller models!
>
> Albert
>
> -----Original Message-----
> From: Peter Gottlieb [mailto:nerd at verizon.net]
> Sent: Monday, July 05, 2010 2:37 PM
> To: jfor at quik.com
> Cc: Albert LaFrance; milsurplus at mailman.qth.net
> Subject: Re: [Milsurplus] Even Worse
>
> 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
>>>>>>>
>>>>>>>
>>>>>>>
>>>>>> _____________________________________________________________
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>>>>>>
>>>>>>
>>>>>>
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>>>>>
>>>>>
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>>
>>
>>
>>
>
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