[jakewins]

I don't claim to know the details of reactive power management, but the primary mechanisms for grid stability in the EU is the "cascade" of services the TSOs procures:

- Fast Frequency Response (FFR), sub-second power adjustment following frequency table

- Frequency Containment Reserve (FCR), ~second power adjustment following frequency table

- Automatic Frequency Restoration Reserve (aFRR), ~second energy production following TSO setpoint signal

- Manual Frequency Restoration Reserve, ~minute energy production following TSO activation signals

My understanding is the primary failure in Spain was that 9 separate synchronous plants that had sold aFRR(?) to the TSO then failed to deliver, so when the TSO algorithms tried to adjust the oscillations, nothing happened. Everything else was kinda "as designed".

[pjc50]

> 9 separate synchronous plants that had sold aFRR(?) to the TSO then failed to deliver, so when the TSO algorithms tried to adjust the oscillations, nothing happened.

Oof. This sounds like a classic of "it's only needed in emergencies, so it's only in emergencies that we find out it doesn't work".

[jakewins]

I don't know about the Spanish market, but at least in the markets I'm involved in aFRR is an "always on" product, the TSO controls your plant with a setpoint that updates in near-real-time throughout the period you've sold to them.. it's not clear to me that the product that wasn't delivered was actually aFRR though, maybe it was something else less frequently called upon.

[amluto]

It likes to me like a major factor was that the grid failed to control voltage, not frequency. Frequency control should be unaffected by transformers.