05000395/LER-2004-002

LER-2004-002, Emergency Diesel Generator Start and Load Due to Momentary Fault on Incoming Feed

Docket Number
Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv)(A), System Actuation
Initial Reporting
ENS 40811	10 CFR 50.72(b)(3)(iv)(A), System Actuation
3952004002R00 - NRC Website

PLANT IDENTIFICATION

Westinghouse - Pressurized Water Reactor

EQUIPMENT IDENTIFICATION

"A" Emergency Diesel Generator (EDG) "A" Residual Heat Removal Pump (RHR) "A" Emergency Feedwater Pump (EFW)

IDENTIFICATION OF EVENT

At 2029 on June 12, 2004, the normal incoming ESF feed (1DA) to VCSNS opened on an undervoltage condition. The "A" EDG started and loads sequenced on as designed. The "A" RHR pump started but did not inject any water into the RCS. The "A" EFW pump started and ran for approximately 7 minutes. Other plant equipment and systems also responded as expected.

At the time of the event a severe thunderstorm was in progress. A lightning strike upstream of the Parr Substation caused multiple breakers to open at the substation and resulted in a temporary loss of 115kV voltage to the substation. This loss of voltage de-energized the VCSNS 115kV ESF line whichwas detected by the 1DA undervoltage and degraded voltage relays. These relays opened the normal and emergency feed breakers to 1DA as designed and the "A" EDG started.

This event was reported under Event Notification EN #40811 at 0223 hours0.00258 days <br />0.0619 hours <br />3.687169e-4 weeks <br />8.48515e-5 months <br /> on June 13, 2004 in accordance with 10CFR 50.72(b)(3)(iv)(A).

EVENT DATE

June 12, 2004

REPORT DATE

August 11, 2004

CONDITIONS PRIOR TO EVENT

Mode 1, 100% Power

DESCRIPTION OF EVENT

At 2029 on June 12, 2004, the normal incoming feed (1DA) to the V. C. Summer Nuclear Station (VCSNS) opened on an undervoltage condition. The "A" EDG started and loads sequenced on as designed. The "A" RHR pump started but did not inject any water into the RCS. The "A" EFW pump started and ran for approximately 7 minutes. Other plant equipment and systems responded as expected.

At the time of the event a severe thunderstorm was in progress. A lightning strike upstream of the Parr Substation caused multiple breakers to open at the substation and resulted in a temporary loss of 115kV voltage to the substation. This loss of voltage de-energized the VCSNS 115kV ESF line which was detected by the 1DA undervoltage and degraded voltage relays. These relays opened the normal and emergency feed breakers to 1DA as designed and the "A" EDG started.

Condition Evaluation Report C-04-1846 was generated to document the event and lessons teamed.

CAUSE OF EVENT

At the time of the event a severe thunderstorm was in progress. A lightning strike upstream of the Parr Substation caused multiple breakers to open at the substation and resulted in a temporary loss of 115kV voltage to the substation. This loss of voltage briefly de-energized the VCSNS 115kV ESF line which was detected by the 1DA undervoltage and degraded voltage relays. These relays opened the normal and emergency feed breakers to 1DA as designed and the "A" EDG started. The 230 kV alternate feed to the "A" ESF bus remained available throughout the event.

Subsequent to the event, SCE&G substation personnel found a faulty breaker at the Parr Substation. This faulty breaker failed to isolate the incoming fault and is the cause for several other lines at the substation being affected. The breaker at the substation has been repaired.

ANALYSIS OF EVENT

The undervoltage and degraded voltage relays associated with 1DA functioned properly upon detecting the loss of voltage on the incoming 115kV line. The "A" EDG started and loads sequenced on as designed. Operators acknowledged alarms and walked down the main control board to ensure equipment was functioning properly.

Building operators were also dispatched to monitor proper operation of some of the more critical equipment such as the EDG, the RHR pump, and the EFW pump. Once operations personnel were satisfied that conditions were stable, operating equipment that was not needed was secured. The "A" RHR pump was secured without injecting any water into the RCS. The "A" EFW pump was also secured after running for approximately 7 minutes. Additional plant equipment was also restored to normal alignment as necessary. Reactor power remained at approximately 100% throughout the event.

ANALYSIS OF EVENT (Continued) The 115kV bus section that feeds VCSNS has three power feeds. The other feeds restored power to the bus within several seconds after the trip. While the normal offsite power source was available within seconds of the initial loss, and the 230kV alternate feed to the "A" ESF bus remained available throughout the event, operations personnel monitored the plant and discussed the event with the SCE&G system dispatcher to ensure conditions were stable prior to realigning the plant to the normal offsite power feed via 1DA. This realignment occurred at approximately 2252 hours0.0261 days <br />0.626 hours <br />0.00372 weeks <br />8.56886e-4 months <br /> on June 12, 2004, and the "A" EDG was subsequently secured at approximately 2300 hours0.0266 days <br />0.639 hours <br />0.0038 weeks <br />8.7515e-4 months <br />.

CORRECTIVE ACTIONS

SCE&G substation personnel have repaired the faulty breaker at the substation. All other equipment, both at the substation and at VCSNS, responded as expected.

VCSNS corrective actions include:

Condition Evaluation Report C-04-1846 was generated to document the event and lessons learned. A discussion of the event will be provided as an operating experience item during operator requalification training.

PRIOR OCCURRENCES

There are no prior occurrences of the loss of the normal incoming ESF feed to the plant due to a lightning induced fault on the system.