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From: KevinJ93 <kevin_es@whitedigs.com>
Newsgroups: sci.electronics.design
Subject: Re: Grand Apagon - Electricity (not) in Spain
Date: Wed, 30 Apr 2025 11:25:55 -0700
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measured o
On 4/30/25 4:08 AM, Liz Tuddenham wrote:
> Carlos E.R. <robin_listas@es.invalid> wrote:
> 
>> On 2025-04-30 11:59, Liz Tuddenham wrote:
>>> Bill Sloman <bill.sloman@ieee.org> wrote:
>>>
>>>> ... pumped hydro storage has the spinning
>>>> turbines, but grid scale batteries have invereters, which can reacta lot
>>>> faster than any spinning turbine,
>>>
>>> I thought the stabilising effect of a spinning turbine was because it
>>> *didn't* react quickly.
>>>
>>> The grid frequency begins to fall so energy from the moving parts is
>>> converted to electrical power which is fed into the grid to increase.
>>> the frequency.  This results in a loss of stored mechanical energy which
>>> causes the turbine to begin slowing down - which is detected by the
>>> control system and used to feed more water/gas/steam into the turbine so
>>> its speed is returned to normal.
>>
>> I understand that the turbine doesn't actually slow down, because the
>> generator starts working as a synchronous motor drawing energy from the
>> network instead; this is detected by the control system and feeds more
>> water/gas/steam, etc.
> 
> That doesn't sound right to me.  If the frequency of the grid is
> dropping and the turbine is running at the correct speed, the mechanical
> energy will flow into the grid as electrical energy and the speed will
> start to drop  ... but the speed can never drop below the grid frequency
> because when the energy flow from the turbine stops there is no longer
> any load on the turbine and it doesn't slow down any further.
> 
> If the turbine lost its source of mechanical power, then it would
> 'motor' and extract energy from the grid - but reverse current detectors
> would promptly disconnect it.
> 
> 

The phase angle of the power generated/consumed will change. The actual 
speed will not change (although strictly speaking there will be a finite 
rate of change of speed to accomodate the change in phase angle).