This, while impressive, is not a routine occurrence. It was due to abnormally high winds. Consider the following quotes from the Guardian article:

"High winds over the weekend supplied 53% of Spain's electricity"

"Experts estimate that by the end of the year, Spain will have provided a quarter of its energy needs with renewables, with wind leading the way ..."

http://www.guardian.co.uk/environment/2009/nov/09/spain-nati...