"Around 12:30, several generators changed their active power output. From 12:32:00 to 12:32:48, concurrent with the voltage rise shown in Figure 1-6, the active power output of large Renewable Energy Sources (RES) generators (higher than 5 MW) in Spain decreased by approximately 500 MW. The RES power plants maintained a fixed power factor, meaning that changes in active power also affected the generators’ reactive
power output.

Additional events (mainly generation-related) occurred from 12:32:00 onwards. Between 12:32:00 and 12:32:57, 208 MW of identified distributed wind and solar generating units in northern and southern
Spain experienced either a fast downwards change of operating point of a unit without a ramping restriction, or a disconnection of the unit due to unknown reasons.

In the same period, there was an increase in net load in the distribution grids of approximately 317 MW, which can be attributed partly to disconnections of small embedded generators < 1 MW (mainly rooftop PV3) and partly to an increase in voltage-dependent load as a
result of a voltage rise. The exact reasons for some of these events are not known."