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From: Bill Sloman <bill.sloman@ieee.org>
Newsgroups: sci.electronics.design
Subject: Re: Grand Apagon - Electricity (not) in Spain
Date: Sat, 3 May 2025 14:10:40 +1000
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On 3/05/2025 6:41 am, john larkin wrote:
> On Fri, 2 May 2025 17:49:48 +0100, liz@poppyrecords.invalid.invalid
> (Liz Tuddenham) 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.
> 
> I used to design steamship throttle and boiler control systems [1]. A
> steamship throttle valve hydraulic actuator is powered by low pressure
> oil (from a standby gravity tank) and slews in a few seconds. But
> serious high-pressure hydraulic actuators have multi-horsepower
> outputs and bandwidths of hundreds of Hz.
> 
> A decent steam valve will nicely overlap the equivalent bandwidth of a
> big generator's inertia. Field control can be made fast too.
> 
> Control engineers would be better at designing stable power systems
> than greenie politicians.

Politicians don't design power systems. They subcontract that job to 
engineers. They may not give the work to the right engineers, but 
greenie politicians are unlikely to be any worse at picking contractors 
than any other kind of politician.

> [1] Big ships are mostly diesels now.
> 
> I was once stranded dead in the water in the Gulf Of Mexico/America,
> with maybe 100 other guys, on a LASH ship sea trial, when the main
> turbine steam valve actuator locked up and had to be disassembled and
> redesigned.

Doesn't sound as if they'd given the job to a good engineer.

-- 
Bill Sloman, Sydney