KYIV — Russia has found a way to defeat Ukraine’s carefully constructed defenses around its electrical infrastructure, using tiny drones guided by fiber-optic cables to slip through protective barriers and destroy critical power equipment in the northern Ukrainian region of Sumy.
Open-source analysis has revealed footage of the new wave of attacks, which was posted on Russian social media platforms and verified by the Centre for Information Resilience, a London-based open-source investigation group. Reuters also independently confirmed the findings.
Throughout the war, Russia has repeatedly targeted Ukrainian energy facilities, particularly in frontline areas. To counter this, Ukrainian authorities built massive concrete protective shells — known as sarcophagi — around high-voltage transformers and draped them with anti-drone netting. The frontline areas are also packed with electronic warfare equipment designed to knock out the radio signals that control enemy drones.
But a new class of small, agile First Person View (FPV) drones connected to operators via fiber-optic cable has rendered those electronic countermeasures useless. As long as the thin, nearly transparent cable remains intact and unobstructed, the drones are completely immune to signal jamming.
Joshua Scriven, an investigator at the Centre for Information Resilience, explained that Russian operators have been punching holes in the protective netting by sending one drone through first to break it open, then guiding a second drone through the gap. Since May, those drones have been maneuvering around the concrete sarcophagi and navigating through ventilation openings to reach the core piece of equipment inside: the autotransformer.
Destroying the autotransformer — valued at approximately $3.5 million in a 330-kilovolt substation — takes down the entire transformer unit, according to Oleksandr Kharchenko, head of the Energy Research Centre in Kyiv.
The Centre for Information Resilience has confirmed at least four successful strikes on large, well-protected 330 kV substations, along with at least four more hits on smaller 110 kV facilities with less protection. According to Deepstate, an independent organization that produces an online battlefield map, the targeted 330 kV substations are located between 16 and 26 kilometers — roughly 10 to 16 miles — from the front lines, highlighting the increasing operational range of these fiber-optic drones.
“I think why they’ve started using them is because of these protective sarcophagi. They protect against missiles and Shaheds,” Scriven said, referring to the heavy-duty drones Russia has previously used in attacks.
A fiber-optic FPV drone can be built for as little as $2,000. “The cost-benefit analysis there is staggering,” Scriven added.
He said the pattern of strikes suggests Russia is pursuing a deliberate strategy: first isolating Ukrainian regions from the national power grid, then blacking them out entirely by hitting local power stations.
The Sumy region has endured intense Russian bombardment since the summer of 2024, when Ukraine launched a cross-border offensive into Russian territory from the province. That push was eventually repelled, after which Russia launched its own incursion into Sumy.
On Wednesday, Ukrainian Defence Minister Mykhailo Fedorov said the security situation in the region had worsened in June. “Russia’s goal is to terrorise people and make life in the border regions unbearable,” he wrote.
The International Criminal Court has issued arrest warrants against senior Russian military commanders in connection with attacks on Ukraine’s power grid between 2022 and 2023. Russia denies deliberately targeting civilians and maintains that all of its strikes serve a military purpose.
