When Cuba’s national grid collapses, as it did for the third time in 10 days on Tuesday, a collective groan spreads across its cities and people wonder, again, whether the island’s antiquated electricity system may soon become unrecoverable.

The 777-mile Caribbean island of 9.5 million people has been sweltering under a six-month-long oil blockade imposed by the United States, part of a pressure campaign to bring down its communist government. But the parlous state of Cuba’s infrastructure goes far further back.