“Attacks on American power systems are likely to be small and localized, according to a cybersecurity firm, casting doubt on the ability of a foreign power to take down broad swaths of U.S. electric systems at once. Given current technology it is not reasonable to expect an enemy to shut down large portions of the U.S grid., but hackers do have the ability to target an individual location, Joe Slowik, an adversary hunter at the cybersecurity firm Dragos, told Fifth Domain at the Black Hat conference.”
Source: Why small cyberattacks on power systems more likely than a long-running blackout