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From: john larkin <jl@glen--canyon.com>
Newsgroups: sci.electronics.design
Subject: Re: The Spanish Grid Drop-out - recently released information.
Date: Thu, 15 May 2025 10:51:30 -0700
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On Thu, 15 May 2025 12:37:24 +0200, "Carlos E.R."
<robin_listas@es.invalid> wrote:

>On 2025-05-15 08:18, Bill Sloman wrote:
>> On 15/05/2025 5:14 am, Carlos E.R. wrote:
>>> On 2025-05-14 16:16, Glen Walpert wrote:
>>>> On Tue, 13 May 2025 07:50:36 -0700, Don Y wrote:
>>>>
>>>>> On 5/13/2025 6:26 AM, Glen Walpert wrote:
>>>>>>> I don't think that using broadcast radio for real time mains grid
>>>>>>> control is a good idea. It would be far too unreliable.
>>>>>>
>>>>>> Point to point RF links have been in use in (mostly hard wired) grid
>>>>>> control SCADA (System Control And Data Acquisition) systems for at
>>>>>> least 30 years, which is when a former employer did some work on a
>>>>>> SCADA upgrade project for the Egyptian Electrical Authority.  A search
>>>>>> on 'SCADA radio link' will turn up several vendors.
>>>>>
>>>>> And they used these to control instantaneous frequency and phase?  Or,
>>>>> just coarse data collection and /supervisory/ control?
>>>>
>>>> SCADA is used to monitor and control the grid, where control is done in
>>>> real time by adjusting the set points for real and reactive power at all
>>>> controlled power sources.  A small percentage of sources being
>>>> inaccessible degrades control by an insignificant amount.
>>>>
>>>> Real power is regulated by the prime mover governors, which must be
>>>> operated in droop mode in order to share the load (the speed set 
>>>> point is
>>>> reduced with increasing load).  The grid Hz/Gw figure which has been
>>>> mentioned is not directly related to generator inertia, where
>>>> insignificant energy is stored, it is the aggregate droop setting of the
>>>> prime mover governors feeding the grid.  After speed/frequency shift 
>>>> (the
>>>> governors only measure shaft speed) due to a load change the grid 
>>>> control
>>>> center adjusts the governor set points to bring the frequency back to
>>>> normal.
>>>>
>>>> Voltage regulation is entirely separate and is done by setting the
>>>> reactive power output of sources, again by adjusting set points in real
>>>> time over SCADA (or one of the other approved standard comm protocols).
>>>> This is a bit complex for a quick explanation but is described in detail
>>>> in any decent text covering synchronous generator control.
>>>>
>>>> Voltage regulation is more likely to be a stability issue than 
>>>> frequency.
>>>> If you take two widely separated generators or sets of locally 
>>>> paralleled
>>>> generators at two power plants which are optimally tuned for stand alone
>>>> operation and connect them with a long transmission line, voltage will
>>>> begin to oscillate due to the time delay in locally detecting changes in
>>>> the other plants output.  Detuning the regulators to achieve stability
>>>> results in inadequate response to load changes - thus central control of
>>>> both plants over SCADA.
>>>>
>>>> Large generator voltage response time is limited by the L/R time 
>>>> constant,
>>>> which will be in the 10's of seconds, over a minute for some large 
>>>> multi-
>>>> pole hydroelectric generators.  Inverters can respond much faster, with
>>>> potentially worse stability issues, and dividing power sources into many
>>>> small units does not make stability any easier, you still can't set
>>>> optimal tuning parameters for widely separated groups of sources which
>>>> will be both stable and fast, central control of some percentage of 
>>>> source
>>>> set points is required.  This problem and it's solution is well 
>>>> understood
>>>> and the current generation of inverters are designed to allow remote
>>>> control of set points.
>>>>
>>>> In the US more than 2/3 of all solar power is utility owned 10 MW or
>>>> larger and all of this is under central grid operator control, so no
>>>> stability issues there.
>>>>
>>>> More intermittent power sources need more batteries, which are being
>>>> deployed by utilities as fast as they can be manufactured, being far
>>>> cheaper then peaking gas turbines, the most expensive of power sources.
>>>>
>>>> <https://www.tdworld.com/distributed-energy-resources/energy-storage/ 
>>>> news/
>>>> 55287560/us-energy-storage-industry-commits-100-billion-investment-in-
>>>> american-made-grid-batteries>
>>>
>>> Wouldn't it be easier to have the entire distribution network using DC?
>>>
>>> just saying with a glass of wine in my hand :-)
>> 
>> That's probably correct, but it wouldn't be cheaper. It's probably true 
>> that taking DC down to the sub-station level could be cheaper, with 
>> today's technology, if you were starting from scratch, but since that 
>> kit is already there you would be throwing away a lot of big expensive 
>> transformers from the next level up, and replacing them with a lot of 
>> big, expensive - if less expensive - inverters. It would take a lot of 
>> capital investment to make the switch, and the people who operate the 
>> grid are adminstrators rather than entrepreneurs.
>
>I'm just thinking that adding sources to a DC distribution network is 
>easier: the voltage just rises or drops. Possibly it autoregulates.
>
>But of course, we have a huge installed system, replacing it would be 
>terribly expensive.
>
>
>Another very wild idea was increasing the frequency to around 600Hz. It 
>would make transformers and all coiled things smaller. Planes do this. 
>Possibly would also radiate more. And would not help with control.

But our clocks would run ten times faster.

And everything would hum.