Any thoughts/information on what happened? Was it a lack of spinning reserve?
Was it " The Portuguese operator, REN, said the outage was caused by a “rare atmospheric phenomenon”, with extreme temperature variations in Spain causing “anomalous oscillations” in very high-voltage lines."
as is written in the Guardian?
The Italien blackout from a few years ago had a definate cause in the tripping of interconnetors from Switzerland during a storm.
The initiating event for this cascade failure was the disconnection of various renewables as is shown in the table starting on page 103. The reasons for the disconnections are not given
As engineers we should also ask WHY things happened thus a reason must be obtained so that future occurrences can be minimised or eliminated altogether.
As you say there is a lot of detail in the report. There were clearly some stability problems before the trip.
Thermal 4–Centre /South-West was meant to be online for voltage control but was unavailable due to internal problems. Thermal 5–Centre/South-West was left connected during the previous night for voltage control but was shut down on the morning of the trip.
The need for more conventional generation with power system stabilisation was recognised and a CCGT plant was ordered to start up, but the trip occurred before it was up to speed.
This is stated here:
2.6.8 Technical Constraints in Spain
“Even if there was not a remunerated voltage control service in place, power plants scheduled by the TSO under PO3.2 to solve situations of lack of dynamic voltage control receive the technical constraints remuneration (pay as bid) for their active power redispatch. In security studies conducted on 27 April, for 28 April, the combined cycle “Thermal 4–Centre /South-West” was scheduled for the entire day to regulate voltage in Western Andalusia. At 19:52 on 27 April, the unit was declared unavailable due to an internal problem, initially until 22:00 on 27 April and later extended to 00:00 on 30 April. The connection of “Thermal 5–Centre/South-West” was extended during the night to secure voltages. During the morning of 28 April, RE considered that the “Thermal 5–Centre/South-West” plant was not needed. There is no operational procedure approved in Spain where a minimum number of generation units coupled is required, and there is also no maximum limit. The criterion to decide the coupling of an additional generation unit is the fulfilment of Operational Procedure 1.1 with foreseen scenarios (generation, demand, and network). At 12:20 on 28 April, RE ordered the connection of an additional thermal power plant equipped with PSS, following the detection of system oscillations. The selected group was a combined-cycle gas plant in centre/south-west, which indicated that it could be connected in 90 minutes. At 12:26, the confirmation was issued to the power plant to connect at 14:00. Due to the blackout occurring before 14:00, this connection never occurred. In general, RE is aware of the start-up times of the combined-cycle gas plants in its control area.”
The initiating event for this cascade failure was the disconnection of various renewables as is shown in the table starting on page 103. The reasons for the disconnections are not given.
It is interesting to note that the restart was carried out using hydro and thermal generation. The renewables were not allowed back online until everything was running stably again.
Thanks for this Roger
However, I disagree: It doesn't suggest that renewables were the cause.
The document is a factual report describing the sequence of events; it explicitly states that the root cause analysis (including determining whether the network operators' actions contributed) is a next step i.e. the cause is not addressed in this report.
Instead the report defines the event as starting at the time that things started tripping. The first things to go were indeed embedded generators. These were mostly renewables, and the actual cause of the trip is not explicitly known, but subsequent trips were due to overvoltage then overfrequency and RoCoF. Because distribution network voltages tend to flap around more than transmission, it is perhaps unsurprising and likely by design that they went first. This does not mean that they were the cause.
(Disclaimer: Obviously I haven't had the chance to read the report in full as it is very dense detail and it was only released today)
The next report from ENTSO-E on the Iberian blackout has now been published:
This suggests that the cause was a large quantity of various renewables going off line.
'Several important generation trips occurred from 12:32:00 onwards. Between 12:32:00.000 and 12:32:57.000, there was a loss of 208MW identified distributed wind and solar generators in northern and southern Spain, as well as an increase in net load in the distribution grids of approximately 317MW, which might be due to the disconnection of small embedded generators <1MW (mainly rooftop PV) or to an actual increase in load or to a combination of both. The reasons for these events are not known. From 12:32:57.000 until 12:33:18.020, major disconnection events occurred in the regions of Granada, Badajoz, Sevilla, Segovia, Huelva, and Cáceres, which resulted in an additional loss of generation of at least 2GW (the effects of frequency deviation suggest a loss of even 2.2GW).'
The reasons for for the trips are not stated.
Hello Paul:
I guess we will have to wait until there are multiple new power system failures before we get to the real root cause of this problem.
Peter
Sorry Peter, I have no knowledge of the Spanish network. Simply trying to relate the various reports which have emerged, and what lessons are to be learnt for the operation of the grid in other countries.
Regards, Paul Adkins
Hello Paul:
Do you know which company manufactured and installed the inverter systems at the Province of Badajoz Photovoltaic Plant A?
Peter Brooks
Palm Bay FL
System operator's report which adds more meat to the government report Mike linked to previously:
Translation by DeepL here
Rgds Paul
In a sense, the "reactive power" phrasing can be a red-herring of a vague assertion that presumes certain aspects of rotating plant, rather than being clear about the grid forming/following, lead-lag, 'instant' power aspects that (IIUC) were/are not being implemented on the wind and solar plants.
In a sense the old codes were playing King Canut against the rising tide, and we are now between a rock and hard place of old control techniques and modern (quire new) electronic mechanisms that were being disallowed (i.e. not having grid forming on those mandated wind/solar supplies).
One has to separate the lead-lag control part of the synthesised sine-wave(s) from the harmonic aspects (esp 3rd) to be able to discuss the wider wicked issues of the blame game.
What is always more interesting is what they are not saying or in other words the ‘Elephant in the Room’ A few points seem to be clear:
Due to the cost of shutting down wind and solar power plants the grid operators are obliged to take all that is available and shut down the rotary plants instead. These Constraint payments are an artificial political requirement not a technical requirement.
The grid had been showing signs of voltage instability previous to the blackout. This was put down to a lack of reactive power control. The effect of the high level of ‘synthesised’ sine waves from wind and solar rather than ‘pure’ sine waves from rotating machines has not really been mentioned other than saying that the grid operator should have been running more gas plants, which goes against the previous financial points.
"The government report also found that REE failed to switch on thermal power stations, which would have helped stabilise the system"
Blaming the grid operator for not running enough gas plants is a tacit admission that they were running too many renewables on cost grounds. No one really seems to want to say that.
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