Both Spain’s and Portugal’s electricity grid operators are reporting that power supplies are returning to normal after a huge power outage that occurred at 11.33am local time on 28th April.
Spain’s operator, Red Eléctrica currently states that 99.95% of demand has been restored and in Portugal REN says that the network has been completely restored in that country.
While speculation about the cause of the incident continues, REN seems to be quite clear that a significant voltage fluctuation occurred in the Spanish grid at a time when Portugal was importing energy from Spain. As a result of the fluctuation the control and protection systems shut down to prevent widespread damage to electrical infrastructure.
Oscillations in very high voltage lines due to unusual weather conditions is a known phenomenon called ‘induced atmospheric vibration’ and this was suggested by a REN spokesperson as the root cause of the incident. This was reported initially by Reuters.
To understand what induced atmospheric vibration is Resilience Forward turned to ChatGPT, which stated that induced atmospheric vibration is a real — though quite rare — phenomenon related to atmospheric conditions causing mechanical vibrations in high-voltage transmission lines, sometimes called ‘aeolian vibrations’ or, in more extreme cases, ‘galloping’. What REN described points toward a broader set of vibration-induced problems that can occur under extreme temperature or wind changes. The resulting oscillations can:
- Change the impedance (effective electrical resistance) along the line.
- Cause fluctuations in power flows.
- Desynchronize large interconnected grids because power systems rely on precise frequency synchronization.
- Trigger protective shutdowns to prevent equipment damage or cascading blackouts.
