The following information was provided by the licensee via phone and email:
At 1351 CST on 11/14/25, with the unit in mode 1 at 99 percent power, an actuation of the division 1, 2, and 3 emergency diesel generators (EDGs) occurred when a fault occurred on the emergency reserve auxiliary transformer (ERAT). The reserve auxiliary transformer `B' was de-energized and isolated for maintenance. The cause of the division 1, 2, and 3 EDGs auto-start was an actuation of the loss of voltage function undervoltage relays for each respective bus. The division 1, 2, and 3 EDGs automatically started as designed when the applicable loss of voltage signals were received.
This event is being reported in accordance with 10 CFR 50.72(b)(3)(iv)(A) as an event that results in a valid actuation of the division 1, 2, and 3 EDGs.
The NRC Resident Inspector has been notified.