On Sunday evening, Ukrainian power engineers returned to work the sole remaining main off-site power line between the Russian-occupied Zaporizhia Nuclear Power Plant and the Ukrainian power system – the 750 kV Zaporizhia NPP-Dniprovska overhead line, thereby preventing the threat of another blackout for the plant.

"Ukrainian specialists repaired the damaged 750 kV line at 08.52 p.m. Until that time, the Zaporizhia NPP had been on the verge of another blackout for almost the entire day, which would have occurred if the backup 330 kV line had lost power connection," Energoatom said in a statement on Monday.

They explained that on November 26, 2023 at 10:30, as a result of a short circuit that occurred around 100 km north of the Zaporizhia NPP captured by the Russians, its sole remaining (out of the four that existed before) line of its connection was disconnected. Three other lines were damaged even earlier by Russian shelling.

According to a report on the International Atomic Energy Agency (IAEA) website, after the 750 kV overhead line was turned off, the Zaporizhia NPP received external power from its only available 330 kV back-up power line.

However, one emergency diesel generator also started operating to supply reactor unit 4 after the power loss, indicating a possible issue with its electrical configuration. The diesel generator was manually shut down after ten minutes.

They recalled that the ZNPP has lost external power supplies repeatedly during the conflict, including seven complete loss of off-site power events. The connection to the 750 kV line was last lost on 10 August, when the line disconnected and was reconnected twice on the same day.

At the same time, the IAEA said that on Sunday, the IAEA experts present at the ZNPP heard several rockets that appeared to have been fired from close to the plant. The IAEA team did not see the projectiles because of clouds but the distinctive sound indicated they were fired from a Multiple Launch Rocket System (MLRS) nearby.

"Today's events once again clearly demonstrate the extremely fragile nuclear safety and security situation at the Zaporizhia Nuclear Power Plant. Europe's largest nuclear power plant – located on the frontline – continues to face many potential threats as a result of this tragic war," IAEA Director General Rafael Grossi said.