Re: Grand Apagon - Electricity (not) in Spain

Liz Tuddenham <liz@poppyrecords.invalid.invalid> wrote:

Bill Sloman <bill.sloman@ieee.org> wrote:
 

On 3/05/2025 12:43 am, john larkin wrote:

On Thu, 1 May 2025 11:24:13 +0100, liz@poppyrecords.invalid.invalid
(Liz Tuddenham) wrote:
 

Chris Jones <lugnut808@spam.yahoo.com> wrote:
>
>

There is nothing magic about the current from a rotating generator that
cannot be exactly replicated by an inverter ...

>
Inertia.  Not magic but physics.   A store of energy that can be drawn
on instantly for several seconds.  Only an inverter with a massive
energy storage system could match that; domestic systems can't.

 
A boiler full of superheated water stores a lot of energy too. And
hydraulic steam valve actuators move fast.

 
Not all that fast. 50Hz is probably more than they could track. 60Hz
would be even more difficult.

 
They have no problem at a few cycles per second, as London Transport
discovered in the early days of computers.
 
London Transport was powered by Lotts Road Power Station.  The load was
mainly underground electric railways, trams and trolleybuses. but they
took the electricity supply for their offices from there too.  The first
computer they installed kept crashing and the problem was traced to dips
in the power supply rails.
 
After a lot of investigation, they discovered that the AC mains supply
had alternate (or perhaps every third) cycles much lower in voltage than
the others (and I think there must have been a timing error too).  The
power supply smoothing capacitors were unable to store enough energy to
tide them over the dips and the result was a regular dropping of the
'stabilised' supply rails.
 
The fault was traced back to Lotts Road, where it was found that a steam
valve was constantly cycling due to an unstable control loop.  This
hadn't had any effect on the trams, so nobody had bothered to do
anything about it.
 
Conclusion:
A tram stores more energy than a computer capacitor bank.

That does not look true.  Reasonably sized generator have a lot
of inertia, so large changes on few cycle basis would mean huge
forces and are likely impossible by changing steam flow.  Even
smaller, but fast changes would mean extra mechanical stress, so
probably would be worth to fix (to get expected equpement life).

If the story about computer crashes is true, there are more
likely reasons.  Our physicits got a building that was previously
used by communist party.  They had trouble with electricity
supply.  On osciloscopes they could see really awful waveforms.
A little investigation showed that the building had common
connection with rectifiers for trams (our trams use DC).
Advantage of this was that power for trams was switched off
only after everthing else in the city, so this was most
reliable power nearby.  But waveform caused trouble for
computers and scientific equipement.

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                              Waldek Hebisch