ML20135H295

Final ASP Analysis - Oconee 2 (LER 270-92-004)

ML20135H295
Person / Time
Site:	Oconee
Issue date:	05/14/2020
From:	Christopher Hunter NRC/RES/DRA/PRB
To:
Littlejohn J (301) 415-0428
References
LER 1992-004-00, LER 269-1992-019, LEr 269-1993-001, LER 269/1992-011, LER 269/1992-014, LEr 269/1992-016, LER 270-1992-004
Download: ML20135H295 (17)

Text

B-89 B.14.2 Event Description On October 19, 1992, Oconee 2 was operating at 100 power. Keowee Hydro Unit l (Keowee 1), one of the emergency power sources for the three Oconee units, was supplying power to the grid via.the overhead power path (see Fig. B.23). Keowee 2 was shut down and was aligned to provide emergency power via the underground path. Replacement of the 230-kV switchyard batteries was in progress:

battery SY-2 and charger SY-2 were disconnected, switcbyard

° de buses SY-DC-1 and SY-DC-2 were cross-tied, and charger SY-1 and battery SY-1 were powering both buses (see Fig. B.24).

Fag. B.23.

Emergency power distribution at Oconee (Original figure was illegible.)

LER NO: 270/92-004 Figure removed during SUNSI review.

B-90 Fig. B.24.

230-kV switchyard de power distribution at Oconee (Original figure was illegible.)

LER NO: 270/92-004 Figure removed during SUNSI review.

B-92 Fig; B.lS.

Keowee Hydro Station ac and de systems.* *

(Original figure was illegi*bl.)

apparently because of the spurious actuation of a lockout rely following a series of repetitive breaker operations that occurred as load center 1 X lost and regained power during the event. As a result, bus lX remained deenergized. ACB-8 failed to close because *of high resistance on a close *permissive contact, which caused auxiliary bus 2X to remain deenergized. The loss of these two buses resulted in the loss of all auxiliary power to the Keowee-units.. The Keowee control room lights went off, e annunciator panels went dark, and the telephone connection to Oconee and the alarm typer. *were lost.

At this point, the Keowee operator determined that" Keowee 2 wa:s running in the emgency mode.* The Keowee units continued to operate with their control functions supplied by batteries.

LER NO: 270/92-004 Figure removed during SUNSI review.