Re: Grand Apagon - Electricity (not) in Spain

On 30/04/2025 01:07, Don Y wrote:

Or, just solar "farms"?

>
They can drop out entire blocks of switchgear to take a given region or zone offline (as would happen if a fault condition trips a breaker).
>
The big problem on a really sunny day is that an individual house roof 4kW PV installation in late afternoon in the UK will be potentially exporting all of it to the grid. That is about 20-30 houses worth of electricity for each solar roof.

 Huh?  A single residential PV is enough to *power* 20 homes?
A 4-5KW installation would barely cover the home on which
it was sited.
 E.g., our "average" (24/7) load is about 1KW.  Of course, that
neglects the peaks that we see OFTEN throughout the daylight
hours (night load is relatively small -- a few LED lights
plus my computers)

Different environment. The temporal average base electricity load of a UK home in summer is somewhere around 200W mostly less unless the kettle (2 mins) or immersion heater (1 hr) is on 3kW. By late afternoon the immersion heater will not be in use as hot water will be fully hot.
Domestic aircon is virtually unknown here. Fridges and freezers come in at about 4-500W but are very intermittent so a working average power consumption for a home is somewhere between 200-300W.
As a calibration point my base load is 100W with no computers on and twice that with my main box on and idle. I have a lot of electronic gadgets running 24/7 too so most homes base load ought to be less!
It crosses my mind now you come to mention it that UK NESO might be using US figures for domestic electricity consumption which would explain why their load shedding sums went so horribly wrong.

They drop say 100MW of load or approx 500k houses @ 200W but with 2% of them generating 4kW then they also drop off 40MW of local generation.

 The 200W figure is mystifying.

Why? We don't have any aircon and in the daytime so the only serious loads are the fridge and the freezer for a few minutes per hour.

 

So the net load shedding is only 60MW which isn't enough to restore the balance and then the cycle repeats until it hits the low frequency total panic limiter. UK stopped it spreading by manual override dropping more than the algorithm wanted but leaving a big area without power.

 Hence my comment about dropping individual loads (cogenerators).
 

It didn't help that by the time they did that the low frequency had put a lot of electric trains into a disabled state requiring a hard reset by a qualified service engineer visit and at random positions on the intercity train lines. The guys who could do that were in short supply.

 "Unforeseen consequences".  A reason simpletons can't deal with
complex systems.

Key assumption was that there are never power cuts in first world countries - but when there are all hell breaks loose. Why they decided it needed an engineer to visit I really don't know.
--
Martin Brown