Blackouts and heat: why the electricity grid goes into crisis in summer

Between Friday and Sunday last year in several Italian cities, including Turin, Bergamo, Sesto San Giovanni and San Giuliano Milanese, voltage drops and power outages have occurred due to the intense heat of recent days. The same phenomenon has hit Naples, where Corso Umberto recorded a blackout that left approximately 300 users without power on the night of June 22nd. But why does the heat wave disrupt the electricity grid so frequently? The reasons are structural and concern the way cables are built, buried, and managed.

How the electricity grid works and why heat damages it

The electrical network of a city is made up of thousands of kilometers of metal cables Surrounded by insulating material and joined together by joints. For example, Unareti, a company that manages distribution in some areas of Italy, has approximately 15 kilometers of cables in the Milan, Brescia, and Bergamo areas alone. When the outside temperature rises, the asphalt heats up and the underground cables they struggle to disperse heat generated by the passage of electricity. At the same time, to combat the heat, people turn on more air conditioners and fans, increasing the flow of energy and therefore heat production in the conductors. The insulation material degrades more rapidly, the joints become more fragile, and at a certain point the flow of electricity stops, leaving the buildings powered by that stretch of cable in darkness.

Why fixing breakdowns is so complicated

When a cable breaks, technicians must intervene under the road, digging to reach the damaged point. The repair involves replacing the damaged section with new joints, but each intervention further fragments the network, increasing the number of weak points. With each patch, explains Alberto Berizzi, professor of Electrical Energy Systems at the Polytechnic University of Milan, trunks become smaller and joints increase, making the grid more fragile and vulnerable. Maintenance is also complicated by the difficulty of predicting where the next damage will occur: heat can damage even new cables, not just worn ones. Furthermore, repair sites impact city traffic and often have to contend with cars parked above excavation sites. Temporary solutions, such as alternative power routes or the use of emergency generators, help limit disruption but do not address the underlying fragility of the grid, which faces the same problem every summer.