The Russian-controlled management of the Zaporizhzhia plant, the largest in Europe, also said the line had been repaired.
"On March 22, Ukrainian energy workers restored the operation of the PL-750kV Dniprovska external overhead line, which was damaged this morning during massive Russian missile strike," Energoatom said in a Telegram post.
Russia launched over 150 missiles and drones overnight in an attack targeting Ukraine's power facilities, according to Kyiv.
The Zaporizhzhia plant was captured by Russian forces shortly after their invasion in 2022. It is shut down and needs external power to keep its nuclear material cool and prevent a catastrophic meltdown.
It is 35 miles (56 km) from Ukraine's biggest hydro-electric dam, which was hit by Russian strikes on Friday, causing blackouts.
The International Atomic Energy Agency said earlier the nuclear power plant had lost connection to its main off-site power line, but that a backup power line was still working.
"Such a situation is extremely dangerous and threatens to lead to an emergency," Petro Kotin, head of Energoatom, said earlier on Telegram.
The plant has been cut off from power several times during the war and has in the past been forced to rely on backup diesel generators, which officials say poses an increased risk of nuclear accident.
The Russian-controlled management of the plant said earlier that one of the two high-voltage lines supplying it with electricity was down but that there was no safety threat.
