How warning signs hinted at Spain's unprecedented power outage

Spain suffered several power glitches and industry officials sounded repeated warnings about the instability of its power grid in the build up to its catastrophic blackout on Monday.

The government has ordered several investigations into the blackout. Industry experts say that whatever the cause, the mass outage and earlier smaller incidents indicate the Spanish power grid faces challenges amid the boom of renewables.

A surplus of energy supply can disrupt power grids in the same way as a deficit, and grid operators must maintain balance.