Sept 7 (Reuters) - Entergy Corp said on Tuesday it has received approvals from the U.S. nuclear regulator to restart its Waterford 3 plant in Louisiana that has been shut since August 29 after Hurricane Ida cut power to the facility, but did not say exactly when that would occur.

"A safe, deliberate power ascension will begin soon," Entergy spokesperson Michael Bowling said about the 1,152 megawatt (MW) plant in Killona, which had received the approvals from the U.S. Nuclear Regulatory Commission.

Bowling did not give details on the restart date. "Due to security and regulated market reasons, we cannot discuss when the facility will reach 100 percent power," he said.

The NRC said on Sept. 3 that the restart would be on Sept. 11.

Entergy had declared on August 29 an "unusual event" at Waterford, the lowest of four levels of nuclear emergency, after the plant lost offsite power. It terminated that event after offsite power was restored on August 31.

Entergy said earlier on Tuesday that 54% of customers across Louisiana have had electricity restored after Ida knocked out power, and that restoration times would extend to no later than Sept. 29 even in the hardest-hit communities.

Ida caused damage to outlying structures at Waterford 3 and its River Bend nuclear 974 MW plant near Baton Rouge, the company has said. River Bend went down to 40% power during the storm as directed by the system dispatcher to "preserve grid integrity." It returned to 100% power on Sept 4.

(Reporting by Timothy Gardner; Editing by Mark Porter)