[time-nuts] 60 Hz measurement party

Will Matney xformer at citynet.net
Sun Jun 26 18:10:50 UTC 2011

I quite like your generator description of "huge rotating lumps of
copper-ensnarled iron". It brings me back to around 20 years ago, when I
was a plant electrician at an older railcar manufacturer. They had huge
open-frame synchronous motors, from around the 1930's, that ran their air
compressors, and why they used this type of motor is anybodies guess. If I
remember right, they were rated at around 200 HP, or so, and were about 8
feet in diameter. The rotor shaft was mounted on huge babbit bearings upon
concrete pillars, and about 1/3 of the motor sat in a pit in the concrete
floor. I used to have to repair the brushes on the slip rings constantly,
until I talked the boss into adding a shunt across the n.o. contacts on the
250 Vdc contactors to quench any arcing. The motors stator itself ran on
4160 Vac. Would the other compressors have to run in sync somehow, as all
of them had these motors, just some a little smaller than the others? They
drove large single cylinder compressors that fed something like a 6 inch
air line (pipe). However, they all did not run at once, and they only did
when there was a larger demand for air. Timing is the only thing I can lay
this to, and was wondering about it.



*********** REPLY SEPARATOR  ***********

On 6/26/2011 at 5:38 PM Poul-Henning Kamp wrote:

>In message <4E066FAC.5090709 at rubidium.dyndns.org>, Magnus Danielson
>>Infact, Poul-Henning and I had the idea to test this on our grid to see 
>>what kind of performance we would get out of it. He sent me a 
>>transformer prepped for the work, but it seems both of us got caught up 
>>doing other stuff to follow through, but this is a good trigger.
>Yeah, life, don't talk to me about life... :-)
>Actually what I wanted to measure back then was the phase-stiffness
>of the grid between us.
>This may be relevant to Tom's experiment as well, and in particular
>to those of you living in California, so let me explain what it is:
>Imagine two time-nuts, N1 and N2, two generators G1 and G2 and
>various chains of transformators T1a... and T2a... in the same
>powergrid but some n*100km apart.
>G1 --- T1a -+- T1b ------------------------T2b -+- T2a --- G2
>            |                                   |
>           T1c                                 T2c
>            |                                   |
>           N1                                  N2
>If all the power is generated by G1, the absolute GPS relative
>phase seen at N1, depends on G1, T1a and T1c, which N2 sees
>the combined effects og G1, T1a, T1b, T2b, T2c.  When G2 produces
>all the power, the picture reverses and when G1 and G2 each produce
>half the phase difference btween N1 and N2 should be constant.
>(But not zero, because they may not be on the same of the three
>phases and because grid transformers shifts phases around to match
>things up.  Long story, not for today.)
>Which way you push power through T1b and T2b affects what they do
>to the phase of the grid on either side so the phase difference
>seen between N1 and N2 depends on how power flows in the grid.
>The reason everybody in the same grid sees the same frequency, is
>that when you have a big heavy generator, frequency is a usable
>proxy measurements for energy.
>If you add an electrical load, the generator have to produce more
>electricity which takes more mechanical work causing the
>turbine to slow down.  And vice versa.
>Typically, a frequency deviation of as little as 0.02 % will cause
>regulation of turbine steam.
>Load changes also cause the voltage to change, but this is much
>less pronounced and much harder to measure/regulate with, primarily
>because of the very noisy measurements.
>So the power-grid basically doesn't use voltage for regulation.
>Various mechanisms keep the voltage inside a +/- 10% tolerance 
>at various points and that's that.
>With me so far ?
>All this breaks down once we start adding power-producers which
>are not based on huge rotating lumps of copper-ensnarled iron.
>Solar cells, wind generators, HVDC transmission, electrical cars
>feeding battery power and all these other fancy modern things, feed
>power into the grid with a computer controlled switch mode gadget
>which just tracks whatever phase and frequency your grid has right
>When the frequency changes on one of these switchmodes, they just
>follow the grid, they do not try to join in on the "voting" on
>the frequency by trying to pull the grid ahead or behind depending
>on their power-state.
>As the grid moves from big rotating lumps of iron to switch mode
>attachment, a larger and larger fraction of the generation capacity
>free-wheels in the frequency 'voting'.
>At some point, the system will no longer be stable, and something
>has to happen.
>My particular corner of the world is ground-zero for this, because
>we generate 1/5th of our electricity with windmills and have
>relatively little rotating machinery running in good winds.
>So far, we are not approaching instability, at least not so that
>anybody will admit it.
>But the way to tell if instability is approaching, is to monitor
>the phase difference between N1 and N2 as explained above, the
>larger variations and the more resonance frequencies manifest
>themselves therein, the more you should get involved in local
>The future of grid regulation is to move to a "absolute frequency"
>model, where the frequency is UTC-locked through-out the grid, and
>regulation happens only on voltage.
>There is a lot of fancy technology involved in this, and som scary
>propositions about what we can and can not do with "holistic grid
>regulation" and other such buzzwords.
>Really long term, Edison will win and long-haul electricity will
>all happen on HVDC lines.  When we get buck/boost converters working
>directly on HVDC, everything will be much simpler and stabler, so
>people are seriously dragging their feet.
>My idea for measuring this, was to measure the time from the
>utc second from a GPS receiver to the first zero-crossing of
>the grid, and try plot Magnus and my measurements together.
>Poul-Henning Kamp       | UNIX since Zilog Zeus 3.20
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