ML13330A013

LER 2013-001-01 for Virgil C. Summer Unit 1 Regarding Grid Disturbance Results in an Engineering Safeguard Features Actuation of the a EDG

ML13330A013
Person / Time
Site:	Summer
Issue date:	11/19/2013
From:	Gatlin T D SCANA Corp, South Carolina Electric & Gas Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
LER 13-001-01
Download: ML13330A013 (4)

Text

01Thomas D. GatlinVice President, Nuclear Operations 803.345.4342 November 19, 2013A SCANA COMPANYDocument Control DeskU. S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS),

UNIT 1DOCKET NO. 50-395OPERATING LICENSE NO. NPF-12LICENSEE EVENT REPORT (LER 2013-001-01)

GRID DISTURBANCE RESULTS IN AN ENGINEERED SAFEGUARD FEATURES ACTUATION OF THE "A" EDGAttached is Licensee Event Report (LER) 2013-001-01, for the Virgil C. SummerNuclear Station (VCSNS).

This report describes the grid disturbance that initiated anEngineered Safeguard Features actuation of the "A" Emergency Diesel Generator.

Thisreport is submitted in accordance With 1OCFR50.73(a)(2)(iv)(A) and1 OCFR50.73(a)(2)(iv)(B)(8).

Should you have any questions, please call Mr. Bruce Thompson at (803) 931-5042.

Very truly yours,Thomas D. GatlinRLP/TDG/ts Attachment c: K. B. MarshS. A. ByrneJ. B. ArchieN. S. CarnsJ. H. HamiltonJ. W. WilliamsW. M. CherryV. M. McCreeS. A. WilliamsNRC Resident Inspector QA Manager -M. N. BrownePaulette Ledbetter J. C. MelletteEPIX Coordinator K: M. SuttonINPO Records CenterMarsh USA, Inc.Maintenance Rule EngineerNSRCRTS (CR-13-01346)

File (818.07)PRSF (RC-13-0173)

J'A 96Virgil C. Summer Station .Post Office Box 88. Jenkinsville, SC -29065 -F (803) 941-9776 NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB: NO. 3150-0104 EXPIRES:

10131/2013 (10-2010)

Estimated burden per response to comply with this mandatory collection request:

80 hours9.259259e-4 days <br />0.0222 hours <br />1.322751e-4 weeks <br />3.044e-5 months <br />.Reported lessons learned are incorporated into the licensing process and fed back to indushy.Send comments regarding burden estimate to the FOIA, Privacy and Information Collections

.LICENSEE EVENT REPORT (LER) Branch (T-5 F53), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or byinternet e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information (See reverse for required number of and Regulatory

Affairs, NEOB-10202, (3150-0104),

Office of Management and Budget,digits/characters for each block) Washington, DC 20503. If a means used to impose an information collection does not display acurrently valid OMB control number, the NRC may not conduct or sponsor, and a person is notrequired to respond to, the information collection.

1. FACILITY NAME 2. DOCKET NUMBER 3. PAGEV. C. SUMMER NUCLEAR STATION, UNIT 1 05000 395 OF4. TITLEGRID DISTURBANCE RESULTS IN AN ENGINEERED SAFEGUARD FEATURES ACTUATION OF THE "A" EDG5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVEDSEQUENTIAL REV MONTH DAY YEAR FACILITY NAME DOCKET NUMBERMNUMBER NO. 05000FACILITY NAME DOCKET NUMBER03 24 2013 2013 .1 1 11 19 2013 050009. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply)M 5 20.2201(b)

E] 20.2203(a)(3)(i)

E] 50.73(a)(2)(i)(C)

[] 50.73(a)(2)(vii)

MODE 5 20.2201(d)

[] 20.2203(a)(3)(ii)

H 50.73(a)(2)(ii)(A)

E] 50.73(a)(2)(viii)(A)

LI 20.2203(a)(1)

[] 20.2203(a)(4) 50.73(a)(2)(ii)(B)

E] 50.73(a)(2)(viii)(B)

LI 20.2203(a)(2)(i)

E] 50.36(c)(1)(i)(A) jJ 50.73(a)(2)(iii)

[J 50.73(a)(2)(ix)(A)

10. POWER LEVEL 20.2203(a)(2)(ii)

U 50.36(c)(1)(ii)(A)

/ 50.73(a)(2)(iv)(A) 50.73(a)(2)(x) 20.2203(a)(2)(iii)

U 50.36(c)(2) 50.73(a)(2)(v)(A)

H 73.71 (a)(4)0% 20.2203(a)(2)(iv) 50.46(a)(3)(ii)

U 50.73(a)(2)(v)(B) jj73.71(a)(5)

E] 20.2203(a)(2)(v)

[ 50.73(a)(2)(i)(A)

[ 50.73(a)(2)(v)(C)

[ OTHER20.2203(a)(2)(vi)

[ 50.73(a)(2)(i)(B)

[ 50.73(a)(2)(v)(D)

Specify in Abstract belowor in NRC Form 366A12. LICENSEE CONTACT FOR THIS LERFACILITY NAME TELEPHONE NUMBER (Include Area Code)V. C. SUMMER NUCLEAR STATION, UNIT 1 8039315042

13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORTMANU- REPORTABLE MANU- REPORTABLE CAUSE SYSTEM COMPONENT FACTURER TO EPIX CAUSE SYSTEM COMPONENT FACTURER TO EPIX14. SUPPLEMENTAL REPORT EXPECTED

15. EXPECTED MONTH DAY YEARSUBMISSION YES (If yes, complete

15. EXPECTED SUBMISSION DATE) [] NO DATEABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines)1.0 ABSTRACTOn 3/24/2013 at 0458, a grid disturbance caused an undervoltage relay actuation on the "A" train 7200 Volt Switchgear Bus and the automatic start of the standby "A" Emergency Diesel Generator (EDG). At the time of the event, the "A" trainSwitchgear Bus was aligned to its normal offsite 115 kV power source. The grid disturbance was longer in duration thanthe associated undervoltage relay delay time. However the undervoltage event did not exist long enough to trip openthe normal incoming breaker or initiate the Engineered Safety Features Load Sequencer (ESFLS).

The EDG came up tothe rated frequency and voltage, but the output breaker did not close, which was as expected.

At 0520 the EDG wassecured and restored to standby.

The station was in Mode 5 for a mid cycle outage. All station equipment and alltransmission system equipment operated as designed.

Corrective actions to minimize the probability of reoccurrence have been added to the station's corrective action program.

The event is reportable per 1 OCFR50.73(a)(2)(iv)(A),

and1 0CFR50.73(a)(2)(iv)(B)(8).

NRC FORM 366 (10-2010 NRC FORM 366A LICENSEE EVENT REPORT ( U.S NUCLEAR REGULATORY COMMISSION (10-2010)

CONTINUATION SHEET1. FACILITY NAME 2. DOCKET 6. LER NUMBER 3. PAGEV. C. SUMMER NUCLEAR STATION YEAR SEQUENTIAL R EUNIT 1 05000 395 2 OF 32013 -001 -01NARRATIVE 2.0 EVENT DESCRIPTION At 0458 on 3/24/2013 a grid disturbance caused an undervoltage relay actuation on the 7200 Volt Switchgear Bus(XSW1DA).

This resulted in automatic start of the "A" standby Emergency Diesel Generator (EDG). At the time,XSWIDA was aligned to its normal offsite 115 kV power source (Parr ESF Line). The grid disturbance was caused by alightning strike, which resulted in a momentary voltage depression on the Parr ESF Line. The voltage dipped low enough toactuate the Loss of Voltage Relays (LVR) XSW1DA 10-27-1DA-1(2)(3) that are the supervisory relays for the incomingbreakers for XSW1DA. The grid disturbance did not last long enough to cause the normal incoming breaker on XSW1DAto open, or initiate the Engineered Safety Features Load Sequencer (ESFLS).

The "A" EDG came up to the ratedfrequency and voltage, but the output breaker did not close, which was as expected since XSWIDA normal incomingbreaker did not open.3.0 EVENT ANALYSISThe initial cause of this event was a lightning strike in the vicinity of the two 115kV lines between the Parr substation andthe Denny Terrace substation that resulted in actuation of breakers on both lines. Data provided by Power Deliveryindicated simultaneous phase to ground faults on these lines. As a result, breaker pairs 1421 (Parr) -8062 (Denny Terrace)and 1321 (Parr) -8052 (Denny Terrace) operated to clear the faults. The voltage on the VCS-Parr ESF Line fell toapproximately 0 percent, recovered above 80 percent in approximately 41 cycles (0.68 seconds) and further recovered above91.34 percent in approximately 44 cycles (0.73 seconds).

Power Delivery line crews inspected the lines and found no evidence of debris hitting the line, which excluded this being awind related event. Power Delivery was able to identify a lightning strike from the Fault Analysis Lightning LocationSystem and corroborated the results with Relaying Applications line voltage data. Power Delivery and VCSNS determined the event was a lightning strike in the close proximity to the lines.The offsite 115 kV power source is monitored by Loss of Voltage Relays (LVR) XSWIDA-10-27-1DA-1(2)(3) and theirassociated timer relays. The purpose of the LVRs is to detect a rapid voltage dip as represented by this event. The EDGsare designed to auto start when the LVR detects the bus voltage falling to its setpoint, with a 0.25 second time delay. Oncethe LVRs actuate, a signal is provided to start the EDG and, in parallel, initiate a 2 second timer relay. This 2 second timer,in parallel, starts the ESFLS and initiates an additional timer before the EDG breaker close signal is sent. The sequencestops if the voltage recovers above the relay reset value before the timer times-out.

This process is detailed in FSAR Figure8.3-0o.In this event, the voltage recovered above 80 percent in approximately 41 cycles (0.68 sec). This was quick enough (less than2 seconds) to reset the LVRs and cancel the timer sequence which prevented the ESFLS from initiating its first significant operation (clearing the busses).

Based on this logic, and given the duration of the voltage depression on the 115kV system,the EDG and the ESFLS operated as designed.

The remaining plant equipment affected by the voltage dip operated as designed.

NRC FORM 366A (10-2010)

I.NRC FORM 366A(10-2010)

LICENSEE EVENT REPORT (LER) U.S. NUCLEAR REGULATORY COMMISSION CONTINUATION SHEET2. DOCKET I6. LER NUMBER1 3. PAGEV. C. SUMMER NUCLEAR STATIONUNIT 1SEQUENTIAL NUMBERREVNO.3 OF 32013001 .01INARRATIVE 4.0 SAFETY SIGNIFICANCE The safety significance of this event was minimal.

The station was in Mode 5 for a mid cycle outage. The grid disturbance caused an undervoltage relay actuation on the 7200 Volt Switchgear Bus (XSWIDA) as designed.

This resulted in automatic start of the "A" standby EDG but due to the short undervoltage

duration, and relay time delays, the normal incomingbreaker did not trip open and the ESFLS did not initiate.

All station equipment and all transmission system equipment operated as designed.

5.0 PREVIOUS OCCURRENCE VCSNS experienced a similar event reported by Event Notification EN #40811 on June 13, 2004 and by letter under LicenseeEvent Report (LER 2004-002-00) on August 11, 2004. This event was due to a lightning strike on the same 115 kV offsitepower source but did result in sequenced loads by ESFLS.6.0 CORRECTIVE ACTIONSAll station equipment and transient system equipment operated as designed.

To prevent the probability of similar eventsoccurring in the future, the Power Delivery Department has been requested to inspect and improve, where necessary, thetransmission tower grounding devices on the 115 kV lines. This request has been entered into the station corrective actionprogram.INRC FORM 366A (10-2010)