RC-18-0049, LER 2018-001-01 Tor Virgil C. Summer, Unit 1, Valid Actuation of Emergency Diesel Generator

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LER 2018-001-01 Tor Virgil C. Summer, Unit 1, Valid Actuation of Emergency Diesel Generator
ML18127B707
Person / Time
Site: Summer South Carolina Electric & Gas Company icon.png
Issue date: 05/07/2018
From: Lippard G A
South Carolina Electric & Gas Co
To:
Document Control Desk, Office of Nuclear Reactor Regulation
References
818.07, CR-18-00268, RC-18-0049 LER 2018-001-01
Download: ML18127B707 (5)
v • d • e


Text

A SCANA COMPANY George A. Lippard Vice President, Nuclear Operations 803.345.4810 May 7, 2018 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Sir / Madam:

Subject:

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS), UNIT 1 DOCKET NO. 50-395 OPERATING LICENSE NO. NPF-12 LICENSEE EVENT REPORT (LER 2018-001-01)

VALID ACTUATION OF EMERGENCY DIESEL GENERATOR Attached is the revised Licensee Event Report (LER) 2018-001-01, for the Virgil C. Summer Nuclear Station. This report describes the actuation of the 'A' Emergency Diesel Generator caused by the loss of the 115 kV power supply to the normal incoming Engineered Safety Features power supply to the safety related bus 1 DA. This report is submitted in accordance with 10 CFR 50.73(a)(2)(iv)(A).

Should you have any questions, please call Mr. Michael S. Moore at (803)345-4752.

Very truly yours, BAB/GAL/nk Attachment c: J.E. Addison W.K. Kissam J. B. Archie J. H. Hamilton G. J. Lindamood

W. M. Cherry C. Haney S. A. Williams **r> George A. Lippard NRC Resident Inspector

L.W. Harris

Paulette Ledbetter

J.C. Mellette ICES Coordinator

K.M. Sutton INPO Records Center Marsh USA, Inc. Maintenance Rule Engineer NSRC RTS (CR-18-00268)

File (818.07) PRSF (RC-18-0049)

V. C. Summer Nuclear Station

  • P. 0. Box 88
  • 29065
  • F (803) 941-9776

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 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 industry.

Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.

Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. if a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME V.C. Summer Nuclear Station, Unit 1 2. DOCKET NUMBER 05000 395 3. PAGE 1 OF 4 4. TITLE VALID ACTUATION OF EMERGENCY DIESEL GENERATOR
5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR Y p . P SEQUENTIAL REV Y AK NUMBER NO. MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 05000 01 18 2018 2018 - 001 - 01 05 07 2018 FACILITY NAME DOCKET NUMBER 05000 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 [] 20.2201(b)
  • 20.2203(a)(3)(i)
  • 50.73(a)(2)(ii)(A)
  • 50.73(a)(2)(viii)(A) 1 : ] 20.2201(d)

[ l 20.2203(a)(3)(ii)

  • 50.73(a)(2)(ii)(B)
  • 50.73(a)(2)(viii)(B) 1 ] 20.2203(a)(1) 20.2203(a)(4)
  • 50.73(a) (2) (iii)
  • 50.73(a)(2)(ix)(A) 1 ] 20.2203(a)(2)(i)
  • 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iv)(A)
  • 50.73(a)(2)(x)
10. POWER LEVEL 100 ] 20.2203(a)(2)(ii)
  • 50.36(c)(1)(ii)(A)
  • 50.73(a) (2) (v)(A)
  • 73.71(a)(4)
10. POWER LEVEL 100 ] 20.2203(a)(2)(iii)
  • 50.36(c)(2)
  • 50.73(a)(2)(v)(B)
  • 73.71(a)(5)
10. POWER LEVEL 100 ] 20.2203(a)(2)(iv)
  • 50.46(a)(3)(ii)
  • 50.73(a)(2)(v)(C)
  • 73.77(a)(1)
10. POWER LEVEL 100 ] 20.2203(a)(2)(v)
  • 50.73(a)(2)(i)(A)
  • 50.73(a)(2)(v)(D)
  • 73.77(a)(2)(i)
10. POWER LEVEL 100 ] 20.2203(a)(2)(vi)
  • 50.73(a)(2)(i)(B)
  • 50.73(a)(2)(vii)
  • 73.77(a)(2)(H)
10. POWER LEVEL 100
  • 50.73(a)(2)(i)(C)

OTHER Specify in Abstract below or in NRC Form 366A 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT Michael Moore, Manager Nuclear Licensing TELEPHONE NUMBER (Include Area Code) (803)345-4752

13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT FACTURER REPORTABLE TO EPIX CAUSE SYSTEM COMPONENT FACTURER REPORTABLE TO EPIX NA NA NA NA NA NA NA NA NA NA 14. SUPPLEMENTAL REPORT EXPECTED YES (If yes, complete 15. EXPECTED SUBMISSION DATE) [/] NO 15. EXPECTED SUBMISSION DATE MONTH DAY YEAR 14. SUPPLEMENTAL REPORT EXPECTED YES (If yes, complete 15. EXPECTED SUBMISSION DATE) [/] NO 15. EXPECTED SUBMISSION DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On January 18, 2018 at 1202 [EST], V.C. Summer Nuclear Station (VCSNS) lost one of its two redundant offsite power supplies.

The loss of the 115 kV offsite power supply created an undervoltage condition on the normal incoming Engineered Safety Features (ESF) power supply to the safety related bus IDA. The 'A' Emergency Diesel Generator (EDG) started and loads sequenced as designed.

All plant equipment and systems responded as expected.

All loads were transferred back to the offsite 115 kV power supply at 1318 [EST], The EDG was secured at 1321 [EST], and reset for auto start. Reactor power remained at 100% throughout the event. NRC FORM 366 (04-2017)

NRC FORM 366A (04-2017)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) CONTINUATION SHEET ***** (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gOv/readina-rm/doc-collections/nureas/staff/sr1022/r3/t APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 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 industry.

Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME V.C. Summer Nuclear Station, Unit 1 2. DOCKET NUMBER 05000-3. LER NUMBER YEAR 2018 SEQUENTIAL NUMBER 001 REV NO. 01 NARRATIVE 1.0 EVENT DESCRIPTION On January 18, 2018 at 1202 [EST], VCSNS lost one of its two redundant offsite power supplies.

The Parr Substation supplies the 115 kV offsite power supply to VCSNS. Emergent maintenance at the offsite Parr Substation resulted in an inadvertent opening of breaker #1802 in the Parr Substation.

The loss of the power supply created an undervoltage condition on the normal incoming ESF power supply to the safety related bus 1 DA. The 'A' EDG started and loads sequenced as designed.

The 'A' Residual Heat Removal Pump started but did not inject any water into the Reactor Coolant System. The 'A' Emergency Feedwater pump started and ran for approximately 2 minutes. All other plant equipment and systems also responded as expected.

The normal power supply for the other required offsite power source remained available throughout the event. Operations personnel monitored the plant and verified conditions were stable prior to realigning the plant to normal feed and securing the EDG. All loads were transferred back to the offsite power supply at 1318 [EST], The EDG was secured at 1321 [EST], and reset for auto start. An Apparent Cause Evaluation was performed on the #1802 breaker trip. System control received a station alarm at the Parr Substation.

The alarm was a common alarm to eight circuit breakers (including breaker #1802) which signaled low gas and/or low spring tension. A journeyman electrician was sent to investigate.

The journeyman electrician used a voltmeter to check the DC alarm output of the Gas Density Monitor (GDM) on breaker #1802. When the leads of the voltmeter were placed on the GDM alarm output, breaker #1802 tripped and the sulfur hexafluoride (SF6) lockout rolled. The journeyman checked the SF6 gas gauge, which was above the trip level, then reset the lockout and closed breaker #1802. The apparent cause evaluation discovered that placing meter leads on the GDM can displace the gauge by 2-3 pounds. It was also discovered that the alarm was due to a SF6 gas leak on the center tank of breaker #1802.

The SF6 gas leak decreased the GDM pressure resulting in a smaller distance between the trip contacts.

Additionally, it was discovered that the SF6 gas gauge was reading approximately 3 psig higher than what was present in the circuit breaker. The faulty gauge indicated a greater margin for automatic operation of the breaker lockout than was actually present. This combination of circumstances resulted in the inadvertent tripping of breaker #1802 due to contact of the voltmeter leads to the GDM. 2.0 EVENT ANALYSIS The SCE&G transmission system supplies offsite power for operating the ESF buses as well as for startup and shutdown of the station. One power source is the SCE&G transmission grid terminating at the VCSNS 230 kV switchyard bus, which feeds the plant through a step down transformer.

The second power source is from the offsite Parr Generating Complex over a 115 kV transmission line. This source is connected to the plant through onsite step down transformers and a separate regulating transformer.

NRC FORM 366A (04-2017)

Page 2 of 4 NRC FORM 366A (04-2017)

Page 3 of 4 NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (04-2017)

/w* LICENSEE EVENT REPORT (LER) *W/ CONTINUATION SHEET ° ****** (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/readina-rm/doc-collections/nureas/staff/sr1022/r3/)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 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 industry.

Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. LER NUMBER NARRATIVE 5.0 CORRECTIVE ACTIONS REV NO. 01 An apparent cause evaluation was performed under CR-18-00268.

The following corrective actions were generated:

1. The SF6 gas leak on breaker #1802 was corrected and the SF6 gas gauge was replaced.
2. An SF6 leak check scan was performed during the thermography inspection of the SF6 circuit breakers in the VCSNS Switchyard as part of extent of condition.
3. A step is to be added to SF6 breaker preventative maintenance tasks to perform an SF6 scan prior to removal for testing (CR-18-00268-011).
4. The Low Gas Alarm set point was raised by 3 psi. 5. A caution placard was installed on the breaker #1802 control cabinet door. The placard directs workers to notify the VCS Control room and system control before opening the control cabinet doors. It also alerts the workers that the equipment is sensitive to vibration.
6. The breaker #1802 alarms on the station annunciator were separated to ensure no manual measurements are required for establishing the alarm condition of breaker #1802.
7. An action is being taken to determine which equipment/assets, not owned or maintained by VCS which are scoped in the Maintenance Rule Boundary, should be included in the CMMS database (CR-18-00268-012).

A common cause analysis was performed under CR-18-00670 to evaluate recent transmission issues at and related to VCSNS. The common cause evaluation determined three common causes. First, responsibilities identified in the VC Summer Interfacing Switchyards Agreement (VISA) were not adequately followed.

Second, necessary communications between V.C. Summer, System Control, and Power Delivery Northern Operations employees were not completed prior to execution of work to be performed.

Finally, requirements listed in SCE&G SD-504, "Switching

& Tagging" program were not being completed.

SD-504 is a separate program from V.C. Summer program, SAP-201, "Equipment Tagging and Lockout-Tagout".

Corrective actions have been created to address these issues. The #1802 breaker at the Parr Substation associated with the event is within the Substation Maintenance Rule boundary for the 115kV power supply. The undervoltage on 1 DA ESF bus and subsequent start and loading of 'A' EDG is an unplanned ESF Actuation, which is one of our three Plant Level Performance criteria in the Maintenance Rule Program. The event will be assessed regarding the effectiveness of maintenance per the Maintenance Rule, 10CFR50.65.

NRC FORM 366A (04-2017)

Page 4 of 4 A SCANA COMPANY George A. Lippard Vice President, Nuclear Operations 803.345.4810 May 7, 2018 Document Control Desk U.S. Nuclear Regulatory Commission Washington, DC 20555

Dear Sir / Madam:

Subject:

VIRGIL C. SUMMER NUCLEAR STATION (VCSNS), UNIT 1 DOCKET NO. 50-395 OPERATING LICENSE NO. NPF-12 LICENSEE EVENT REPORT (LER 2018-001-01)

VALID ACTUATION OF EMERGENCY DIESEL GENERATOR Attached is the revised Licensee Event Report (LER) 2018-001-01, for the Virgil C. Summer Nuclear Station. This report describes the actuation of the 'A' Emergency Diesel Generator caused by the loss of the 115 kV power supply to the normal incoming Engineered Safety Features power supply to the safety related bus 1 DA. This report is submitted in accordance with 10 CFR 50.73(a)(2)(iv)(A).

Should you have any questions, please call Mr. Michael S. Moore at (803)345-4752.

Very truly yours, BAB/GAL/nk Attachment c: J.E. Addison W.K. Kissam J. B. Archie J. H. Hamilton G. J. Lindamood

W. M. Cherry C. Haney S. A. Williams **r> George A. Lippard NRC Resident Inspector

L.W. Harris

Paulette Ledbetter

J.C. Mellette ICES Coordinator

K.M. Sutton INPO Records Center Marsh USA, Inc. Maintenance Rule Engineer NSRC RTS (CR-18-00268)

File (818.07) PRSF (RC-18-0049)

V. C. Summer Nuclear Station

  • P. 0. Box 88
  • 29065
  • F (803) 941-9776

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 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 industry.

Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to Infocollects.

Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. if a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME V.C. Summer Nuclear Station, Unit 1 2. DOCKET NUMBER 05000 395 3. PAGE 1 OF 4 4. TITLE VALID ACTUATION OF EMERGENCY DIESEL GENERATOR
5. EVENT DATE 6. LER NUMBER 7. REPORT DATE 8. OTHER FACILITIES INVOLVED MONTH DAY YEAR Y p . P SEQUENTIAL REV Y AK NUMBER NO. MONTH DAY YEAR FACILITY NAME DOCKET NUMBER 05000 01 18 2018 2018 - 001 - 01 05 07 2018 FACILITY NAME DOCKET NUMBER 05000 9. OPERATING MODE 11. THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR §: (Check all that apply) 1 [] 20.2201(b)
  • 20.2203(a)(3)(i)
  • 50.73(a)(2)(ii)(A)
  • 50.73(a)(2)(viii)(A) 1 : ] 20.2201(d)

[ l 20.2203(a)(3)(ii)

  • 50.73(a)(2)(ii)(B)
  • 50.73(a)(2)(viii)(B) 1 ] 20.2203(a)(1) 20.2203(a)(4)
  • 50.73(a) (2) (iii)
  • 50.73(a)(2)(ix)(A) 1 ] 20.2203(a)(2)(i)
  • 50.36(c)(1)(i)(A) 0 50.73(a)(2)(iv)(A)
  • 50.73(a)(2)(x)
10. POWER LEVEL 100 ] 20.2203(a)(2)(ii)
  • 50.36(c)(1)(ii)(A)
  • 50.73(a) (2) (v)(A)
  • 73.71(a)(4)
10. POWER LEVEL 100 ] 20.2203(a)(2)(iii)
  • 50.36(c)(2)
  • 50.73(a)(2)(v)(B)
  • 73.71(a)(5)
10. POWER LEVEL 100 ] 20.2203(a)(2)(iv)
  • 50.46(a)(3)(ii)
  • 50.73(a)(2)(v)(C)
  • 73.77(a)(1)
10. POWER LEVEL 100 ] 20.2203(a)(2)(v)
  • 50.73(a)(2)(i)(A)
  • 50.73(a)(2)(v)(D)
  • 73.77(a)(2)(i)
10. POWER LEVEL 100 ] 20.2203(a)(2)(vi)
  • 50.73(a)(2)(i)(B)
  • 50.73(a)(2)(vii)
  • 73.77(a)(2)(H)
10. POWER LEVEL 100
  • 50.73(a)(2)(i)(C)

OTHER Specify in Abstract below or in NRC Form 366A 12. LICENSEE CONTACT FOR THIS LER LICENSEE CONTACT Michael Moore, Manager Nuclear Licensing TELEPHONE NUMBER (Include Area Code) (803)345-4752

13. COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT CAUSE SYSTEM COMPONENT FACTURER REPORTABLE TO EPIX CAUSE SYSTEM COMPONENT FACTURER REPORTABLE TO EPIX NA NA NA NA NA NA NA NA NA NA 14. SUPPLEMENTAL REPORT EXPECTED YES (If yes, complete 15. EXPECTED SUBMISSION DATE) [/] NO 15. EXPECTED SUBMISSION DATE MONTH DAY YEAR 14. SUPPLEMENTAL REPORT EXPECTED YES (If yes, complete 15. EXPECTED SUBMISSION DATE) [/] NO 15. EXPECTED SUBMISSION DATE ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) On January 18, 2018 at 1202 [EST], V.C. Summer Nuclear Station (VCSNS) lost one of its two redundant offsite power supplies.

The loss of the 115 kV offsite power supply created an undervoltage condition on the normal incoming Engineered Safety Features (ESF) power supply to the safety related bus IDA. The 'A' Emergency Diesel Generator (EDG) started and loads sequenced as designed.

All plant equipment and systems responded as expected.

All loads were transferred back to the offsite 115 kV power supply at 1318 [EST], The EDG was secured at 1321 [EST], and reset for auto start. Reactor power remained at 100% throughout the event. NRC FORM 366 (04-2017)

NRC FORM 366A (04-2017)

U.S. NUCLEAR REGULATORY COMMISSION LICENSEE EVENT REPORT (LER) CONTINUATION SHEET ***** (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gOv/readina-rm/doc-collections/nureas/staff/sr1022/r3/t APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 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 industry.

Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

1. FACILITY NAME V.C. Summer Nuclear Station, Unit 1 2. DOCKET NUMBER 05000-3. LER NUMBER YEAR 2018 SEQUENTIAL NUMBER 001 REV NO. 01 NARRATIVE 1.0 EVENT DESCRIPTION On January 18, 2018 at 1202 [EST], VCSNS lost one of its two redundant offsite power supplies.

The Parr Substation supplies the 115 kV offsite power supply to VCSNS. Emergent maintenance at the offsite Parr Substation resulted in an inadvertent opening of breaker #1802 in the Parr Substation.

The loss of the power supply created an undervoltage condition on the normal incoming ESF power supply to the safety related bus 1 DA. The 'A' EDG started and loads sequenced as designed.

The 'A' Residual Heat Removal Pump started but did not inject any water into the Reactor Coolant System. The 'A' Emergency Feedwater pump started and ran for approximately 2 minutes. All other plant equipment and systems also responded as expected.

The normal power supply for the other required offsite power source remained available throughout the event. Operations personnel monitored the plant and verified conditions were stable prior to realigning the plant to normal feed and securing the EDG. All loads were transferred back to the offsite power supply at 1318 [EST], The EDG was secured at 1321 [EST], and reset for auto start. An Apparent Cause Evaluation was performed on the #1802 breaker trip. System control received a station alarm at the Parr Substation.

The alarm was a common alarm to eight circuit breakers (including breaker #1802) which signaled low gas and/or low spring tension. A journeyman electrician was sent to investigate.

The journeyman electrician used a voltmeter to check the DC alarm output of the Gas Density Monitor (GDM) on breaker #1802. When the leads of the voltmeter were placed on the GDM alarm output, breaker #1802 tripped and the sulfur hexafluoride (SF6) lockout rolled. The journeyman checked the SF6 gas gauge, which was above the trip level, then reset the lockout and closed breaker #1802. The apparent cause evaluation discovered that placing meter leads on the GDM can displace the gauge by 2-3 pounds. It was also discovered that the alarm was due to a SF6 gas leak on the center tank of breaker #1802.

The SF6 gas leak decreased the GDM pressure resulting in a smaller distance between the trip contacts.

Additionally, it was discovered that the SF6 gas gauge was reading approximately 3 psig higher than what was present in the circuit breaker. The faulty gauge indicated a greater margin for automatic operation of the breaker lockout than was actually present. This combination of circumstances resulted in the inadvertent tripping of breaker #1802 due to contact of the voltmeter leads to the GDM. 2.0 EVENT ANALYSIS The SCE&G transmission system supplies offsite power for operating the ESF buses as well as for startup and shutdown of the station. One power source is the SCE&G transmission grid terminating at the VCSNS 230 kV switchyard bus, which feeds the plant through a step down transformer.

The second power source is from the offsite Parr Generating Complex over a 115 kV transmission line. This source is connected to the plant through onsite step down transformers and a separate regulating transformer.

NRC FORM 366A (04-2017)

Page 2 of 4 NRC FORM 366A (04-2017)

Page 3 of 4 NRC FORM 366A U.S. NUCLEAR REGULATORY COMMISSION (04-2017)

/w* LICENSEE EVENT REPORT (LER) *W/ CONTINUATION SHEET ° ****** (See NUREG-1022, R.3 for instruction and guidance for completing this form http://www.nrc.gov/readina-rm/doc-collections/nureas/staff/sr1022/r3/)

APPROVED BY OMB: NO. 3150-0104 EXPIRES: 03/31/2020 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 industry.

Send comments regarding burden estimate to the Information Services Branch (T-2 F43), U.S. Nuclear Regulatory Commission, Washington, DC 20555-0001, or by e-mail to lnfocollects.Resource@nrc.gov, and to the Desk Officer, Office of Information and Regulatory Affairs, NEOB-10202, (3150-0104), Office of Management and Budget, Washington, DC 20503. If a means used to impose an information collection does not display a currently valid OMB control number, the NRC may not conduct or sponsor, and a person is not required to respond to, the information collection.

3. LER NUMBER NARRATIVE 5.0 CORRECTIVE ACTIONS REV NO. 01 An apparent cause evaluation was performed under CR-18-00268.

The following corrective actions were generated:

1. The SF6 gas leak on breaker #1802 was corrected and the SF6 gas gauge was replaced.
2. An SF6 leak check scan was performed during the thermography inspection of the SF6 circuit breakers in the VCSNS Switchyard as part of extent of condition.
3. A step is to be added to SF6 breaker preventative maintenance tasks to perform an SF6 scan prior to removal for testing (CR-18-00268-011).
4. The Low Gas Alarm set point was raised by 3 psi. 5. A caution placard was installed on the breaker #1802 control cabinet door. The placard directs workers to notify the VCS Control room and system control before opening the control cabinet doors. It also alerts the workers that the equipment is sensitive to vibration.
6. The breaker #1802 alarms on the station annunciator were separated to ensure no manual measurements are required for establishing the alarm condition of breaker #1802.
7. An action is being taken to determine which equipment/assets, not owned or maintained by VCS which are scoped in the Maintenance Rule Boundary, should be included in the CMMS database (CR-18-00268-012).

A common cause analysis was performed under CR-18-00670 to evaluate recent transmission issues at and related to VCSNS. The common cause evaluation determined three common causes. First, responsibilities identified in the VC Summer Interfacing Switchyards Agreement (VISA) were not adequately followed.

Second, necessary communications between V.C. Summer, System Control, and Power Delivery Northern Operations employees were not completed prior to execution of work to be performed.

Finally, requirements listed in SCE&G SD-504, "Switching

& Tagging" program were not being completed.

SD-504 is a separate program from V.C. Summer program, SAP-201, "Equipment Tagging and Lockout-Tagout".

Corrective actions have been created to address these issues. The #1802 breaker at the Parr Substation associated with the event is within the Substation Maintenance Rule boundary for the 115kV power supply. The undervoltage on 1 DA ESF bus and subsequent start and loading of 'A' EDG is an unplanned ESF Actuation, which is one of our three Plant Level Performance criteria in the Maintenance Rule Program. The event will be assessed regarding the effectiveness of maintenance per the Maintenance Rule, 10CFR50.65.

NRC FORM 366A (04-2017)

Page 4 of 4

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