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| issue date = 08/27/1993
| issue date = 08/27/1993
| title = LER 93-014-01:on 930722,concern Raised Re 4 Kv Vital Bus Second Level Undervoltage Protection Dropout Setpoint Due to Design,Mfg,Const/Installation.Analysis of Event Continuing. Suppl LER Will Be Submitted
| title = LER 93-014-01:on 930722,concern Raised Re 4 Kv Vital Bus Second Level Undervoltage Protection Dropout Setpoint Due to Design,Mfg,Const/Installation.Analysis of Event Continuing. Suppl LER Will Be Submitted
| author name = PASTVA M J
| author name = Pastva M
| author affiliation = PUBLIC SERVICE ELECTRIC & GAS CO. OF NEW JERSEY
| author affiliation = PUBLIC SERVICE ELECTRIC & GAS CO. OF NEW JERSEY
| addressee name =  
| addressee name =  
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{{#Wiki_filter:NRC FORM 366 (6-89) U.S. NUCLEAR REGULATORY COMMISSION APPROVEO OMB NO. 3150-0104 LICENSEE EVENT REPORT (LER) FACILITY NAME 111 Salem Generating Station -Unit 1 TITLE 141 EXPIRES: 4/30/92 ESTIMATED BUROEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARO COMMENTS REGAROING BUROEN ESTIMATE TO THE RECOR OS ANO REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, QC 20555, ANO TO THE PAPERWORK REOUCTION PROJECT 13150-0104).
{{#Wiki_filter:NRC FORM 366                                                                   U.S. NUCLEAR REGULATORY COMMISSION (6-89)                                                                                                                                    APPROVEO OMB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BUROEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARO LICENSEE EVENT REPORT (LER)                                                        COMMENTS REGAROING BUROEN ESTIMATE TO THE RECOR OS ANO REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, QC 20555, ANO TO THE PAPERWORK REOUCTION PROJECT 13150-0104). OFFICE OF MANAGEMENT ANO BUOGET, WASHINGTON, QC 20503.
OFFICE OF MANAGEMENT ANO BUOGET, WASHINGTON, QC 20503. I OOCKET NUMBER (2) I PAGE 131 01s101010121112 1!0F01S 4KV Vital .Bus Second Level Undervoltage Protection Dropout Setpoint Concern (both Units). EVENT .DATE (5) LER NUMBER 16) REPORT DATE (71 OTHER FACILITIES INVOLVED (Bl MONTH DAY YEAR YEAR :ff tt MONTH DAY YEAR FACILITY NAMES DOCKET NUMBERISI Salem Unit 2 o 15 Io Io I o 13 11 I 1 ol 1 2 I 2 c 3 913 -o I 114 -ol 1 o I s *2 I 1 9 I 3 OPERATING MODE (9) THIS REPORT IS SUBMITTED PURSUANT TO THE Rl.QUIREMENTS OF 10 CFR §: (Chock on* or moro of th* following}  
FACILITY NAME 111                                                                                                                    OOCKET NUMBER (2)                       I       PAGE 131 Salem Generating Station - Unit 1 TITLE 141 I01s101010121112                          1!0F01S 4KV Vital .Bus Second Level Undervoltage Protection Dropout Setpoint Concern (both Units).
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EVENT .DATE (5)                         LER NUMBER 16)                       REPORT DATE (71                       OTHER FACILITIES INVOLVED (Bl MONTH     DAY       YEAR           YEAR   :ff se~~~~~~AL tt ~~~~~~          MONTH       DAY     YEAR             FACILITY NAMES                       DOCKET NUMBERISI Salem Unit 2                                     o 15 Io Io I o 13 11 I 1 ol 1 2 I 2         c 3           913 - oI 114             -       ol 1 o I s *2 I 1 9 I3 OPERATING THIS REPORT IS SUBMITTED PURSUANT TO THE Rl.QUIREMENTS OF 10 CFR         §: (Chock on* or moro of th* following} (11 I I                1 MODE (9) t--~~--..~~            .........-+----l 20.402lbl
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50.731*112llil                     50.7311112llviiillAI                         366A}                  .
73.71(bl 73.71(c) OTHER in Abstroct b1tow 1nd in T..,ct. NRC Form 366A} . TELEPHONE NUMBER M. J. Pastva. Jr. LER Coordinator 6 I 0 I 9 3 I 3 I 9 1-I 5 11 16 I 5 COMPLETE ONE LINE FOR EACH C.OMPONENT FAILURE DESCRIBED IN THIS REPORT (131 . CAUSE SYSTEM COMPONENT I I I I I I I I MANUFAC* TUR ER I I I I I I SUPPLEMENTAL REPORT EXPECTED (14) --;ci YES (If v*i. compl.r* EXPECTED SUBMISSION DATE} ABSTRACT (Limit to 1400 spac6s, i.e., approximately fifteen single-space ty,nwrittan lines} (161
                                                                        -x                                -                                                                                         . i
* I I I I I I I I MANUFAC* TUR ER I I I I I I EXPECTED SUBMISSION DATE 115l MONTH DAY YEAR 1 10 2 15 9 I 3 On 7/22/93, it was determined that the present 91.6% dropout setpoint for second level undervoltage (UV) protection of the 4 kilovolt .(KV) vital buses (both Salem Units), may not fully protect motors should the bus voltage degrade to less than 93.2% but greater than 91.6%. This is contrary to Branch Technical Position (BTP)-PSB-1 and the Updated Final Safety Analysis Report (UFSAR). However, engineering calculation shows, given the postulated worst case design basis event, vital bus recovery voltage will not degrade to less than 93.2%. The 91.6% dropout setpoint was based on the lowest voltage the 4.16 KV motors could be allowed to operate (i.e. 90%) due to voltage drops in the motors' cables and relay inaccuracy considerations.
                                                                        -     li0.73(1ll21Uil
The revised recovery voltage of 93.2% will now maintain all motors operable under degraded voltage conditions.
                                                                                &0.7311112lUiil
During the next refueling outage on each Unit, design changes will be implemented to change the relay setpoint to meet the requirements of BTP-PSB-1.
                                                                                                            -      60.7311ll2llviiillBl 60.731111211xl LICENSEE CONTACT FOR THIS LEA (121 NAME                                                                                                                                                   TELEPHONE NUMBER AREA CODE M. J. Pastva. Jr.                       ~    LER Coordinator                                                                     6 I 0 I 9 3 I 3 I 9 1- I 5 11 16 I 5 COMPLETE ONE LINE FOR EACH C.OMPONENT FAILURE DESCRIBED IN THIS REPORT (131 .
In the interim, administrative controls are being implemented.
MANUFAC*                                                                                MANUFAC*
Technical Specifications and the UFSAR will be reviewed and revised as appropriate.
CAUSE   SYSTEM     COMPONENT TUR ER                                                                                  TUR ER I           I     I   I         I     I I                                               I           I    I    I        I    I    I I            I    I    I          I    I I                                                I          I   I   I         I   I   I SUPPLEMENTAL REPORT EXPECTED (14)                                                                               MONTH        DAY      YEAR EXPECTED SUBMISSION DATE 115l
Analysis of this event is continuing.
--;ci YES (If v*i. compl.r* EXPECTED SUBMISSION DATE}                                                                                                               1 10      2 15 9 I      3 ABSTRACT (Limit to 1400 spac6s, i.e., approximately fifteen single-space ty,nwrittan lines} (161
Upon completion of this effort, a supplement to this LER will be submitted.
* On 7/22/93, it was determined that the present 91.6% dropout setpoint for second level undervoltage (UV) protection of the 4 kilovolt .(KV) vital buses (both Salem Units), may not fully protect motors should the bus voltage degrade to less than 93.2% but greater than 91.6%. This is contrary to Branch Technical Position (BTP)-PSB-1 and the Updated Final Safety Analysis Report (UFSAR). However, engineering calculation shows, given the postulated worst case design basis event, vital bus recovery voltage will not degrade to less than 93.2%. The 91.6% dropout setpoint was based on the lowest voltage the 4.16 KV motors could be allowed to operate (i.e. 90%) due to voltage drops in the motors' cables and relay inaccuracy considerations. The revised recovery voltage of 93.2% will now maintain all motors operable under degraded voltage conditions.
9309030259 930827 I PDR ADOCK 05000272 S * *.PDR NRC Form 366 (6-89) _*-1 . i SUPPLEMENTAL LICENSEE EVENT REPORT (LER} TEXT CONTINUATION Salem Generating Station *unit 1 DOCKET NUMBER 5000272 PLANT AND SYSTEM IDENTIFICATION:
During the next refueling outage on each Unit, design changes will be implemented to change the relay setpoint to meet the requirements of BTP-PSB-1.                       In the interim, administrative controls are being implemented. Technical Specifications and the UFSAR will be reviewed and revised as appropriate. Analysis of this event is continuing. Upon completion of this effort, a supplement to this LER will be submitted.
Westinghouse  
9309030259 930827 PDR ADOCK 05000272 I
-Pressurized Reactor LER NUMBER 93-014-01 PAGE 2 of 5 Energy Industry Identification System (EIIS} codes are identified in the text as {xx} IDENTIFICATION OF OCCURRENCE:
NRC Form 366 (6-89)
4 KV Vitai Bus Second Level Undervoltage Protection Dropout Setpoint Concern (both Salem Units} Event Discovery Date: 7/22/93 Supplement Report Date: 8/27/93 This report was initiated by Incident Report No. 93-320. This event is reportable per 10CFR50.73(a}  
S                              * *.PDR                ~-------------------_.
(2} (ii} (B} and 10CFR50.73(a}  
_*-1
(2} (v} (D}. CONDITIONS PRIOR TO OCCURRENCE:
 
Unit 1: Mode 1 Reactor Power 80% -Unit Load 815 MWe Unit 2: Mode 1 Reactor Power 100% -Unit Load 1140 MWe DESCRIPTION OF OCCURRENCE:
SUPPLEMENTAL LICENSEE EVENT REPORT (LER} TEXT CONTINUATION Salem Generating Station       DOCKET NUMBER      LER NUMBER        PAGE
On July 22, 1993, it was determined that the present 91.6% dropout setpoint for second level undervoltage (UV} protection of the 4 kilovolt (KV} vital buses {VJ} (both Salem Units}, will not fully protect motors at the 230 and 460 volt level should the 4KV bus voltage degrade to less than 93.2% but greater than 91.6%. This is contrary to Branch Technical Position (BTP.}-PSB-1 and the Updated Final Safety Analysis.Report (UFSAR}. However, engineering calculation shows, given the postulated worst case design basis event, vital bus recovery voltage will not degrade to less than 93.2%. The Nuclear Regulatory Commission was notified of this event per Code of Federal Regulations 10CFR50.72(b}  
*unit 1                           5000272           93-014-01        2 of 5 PLANT AND SYSTEM IDENTIFICATION:
(1) (ii) (B). ANALYSIS OF OCCURRENCE:
Westinghouse   - Pressurized Wate~  Reactor Energy Industry Identification System (EIIS} codes are identified in the text as {xx}
Availability of minimum redundant alternating current (A.C.) power sources and distribution systems ensures sufficient power will be available to safety-related equipment for safe shutdown of the facility and the mitigation and control of accident conditions within the facility, as required by General Design Criteria 17 of Appendix "A" to lOCFR Part 50. Per BTP-PSB-1, the plant.licensing basis requires a second level of undervoltage protection for 4KV vital buses to ensure minimum motor terminal voltage for all safety-related  
IDENTIFICATION OF OCCURRENCE:
-. \
4 KV Vitai Bus Second Level Undervoltage Protection Dropout Setpoint Concern (both Salem Units}
.. . SUPPLEMENTAL LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit.1 DOCKET NUMBER 5000272 ANALYSIS OF OCCURRENCE: (cont'd) LER NUMBER 93-014-01 PAGE 3 of 5 motors. At Salem, when vital bus voltage drops below the dropout setpoint for relays providing this protection for greater than 13 seconds, vital bus loads are automatically transferred to their respective emergency diesel generators.
Event Discovery Date:   7/22/93 Supplement Report Date:   8/27/93 This report was initiated by Incident Report No. 93-320. This event is reportable per 10CFR50.73(a} (2} (ii} (B} and 10CFR50.73(a} (2} (v} (D}.
CONDITIONS PRIOR TO OCCURRENCE:
Unit 1:   Mode 1   Reactor Power   80% - Unit Load   815 MWe Unit 2:   Mode 1   Reactor Power 100% - Unit Load 1140 MWe DESCRIPTION OF OCCURRENCE:
On July 22, 1993, it was determined that the present 91.6% dropout setpoint for second level undervoltage (UV} protection of the 4 kilovolt (KV} vital buses {VJ} (both Salem Units}, will not fully protect motors at the 230 and 460 volt level should the 4KV bus voltage degrade to less than 93.2% but greater than 91.6%. This is contrary to Branch Technical Position (BTP.}-PSB-1 and the Updated Final Safety Analysis.Report (UFSAR}. However, engineering calculation shows, given the postulated worst case design basis event, vital bus recovery voltage will not degrade to less than 93.2%.
The Nuclear Regulatory Commission was notified of this event per Code of Federal Regulations 10CFR50.72(b} (1) (ii) (B).
ANALYSIS OF OCCURRENCE:
Availability of minimum redundant alternating current (A.C.) power sources and distribution systems ensures sufficient power will be available to safety-related equipment for safe shutdown of the facility and the mitigation and control of accident conditions within the facility, as required by General Design Criteria 17 of Appendix "A" to 10CFR Part 50. Per BTP-PSB-1, the plant.licensing basis requires a second level of undervoltage protection for 4KV vital buses to ensure minimum motor terminal voltage for all safety-related
                                                                                -. \
 
            . SUPPLEMENTAL LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station         DOCKET NUMBER    LER NUMBER      PAGE Unit.1                             5000272         93-014-01      3 of 5 ANALYSIS OF OCCURRENCE:     (cont'd) motors. At Salem, when vital bus voltage drops below the dropout setpoint for relays providing this protection for greater than 13 seconds, vital bus loads are automatically transferred to their respective emergency diesel generators.
* As part of the self-initiated Electrical Engineering Self-Assessment Program, electrical calculations are being reviewed to ensure guidelines of BTP-PSB-1 are met. On July 1, 1993, review of Revision 1 of ES-15.00S(Q), "Salem Units 1 and 2 Degraded Grid study" identified a potential concern with the 91.6% dropout setpoint of the Units' 4KV vital buses (lA, lB, lC, 2A, 2B, and 2C). on
* As part of the self-initiated Electrical Engineering Self-Assessment Program, electrical calculations are being reviewed to ensure guidelines of BTP-PSB-1 are met. On July 1, 1993, review of Revision 1 of ES-15.00S(Q), "Salem Units 1 and 2 Degraded Grid study" identified a potential concern with the 91.6% dropout setpoint of the Units' 4KV vital buses (lA, lB, lC, 2A, 2B, and 2C). on
* July 22, 1993, further analysis of this concern determined the recovery vital bus voltage is 93.2% of 4.16KV following transfer of the Auxiliary Power Transformers (APTs) to the Station Power
* July 22, 1993, further analysis of this concern determined the recovery vital bus voltage is 93.2% of 4.16KV following transfer of the Auxiliary Power Transformers (APTs) to the Station Power
* Transformers (SPTs). This voltage could result should a group bus transfer to the SPTs occur coincident with a Loss-of-Coolant Accident (LOCA) and the unaffected unit in startup or shutdown.
* Transformers (SPTs). This voltage could result should a group bus transfer to the SPTs occur coincident with a Loss-of-Coolant Accident (LOCA) and the unaffected unit in startup or shutdown.
UFSAR Section 8.3.1.2 describes the setpoint as being determined using the 90% minimum motor terminal voltage as the starting point. Since 93.2% bus voltage is required to ensure the minimum motor terminal voltage, the existing 91. 6% dropout setpoint is not in compliance with the UFSAR or the BTP. However, because ES-15.00S(Q) calculations also show that vital bus recovery voltage will not degrade to a level at which actual motor degradation could occur, the intent of the UFSAR and BTP is still met. These calculations take credit for operation, prior to the event, of the load tap changers which are set to maintain a minimum initial bus.voltage of 4.3KV. Following  
UFSAR Section 8.3.1.2 describes the setpoint as being determined using the 90% minimum motor terminal voltage as the starting point.
*event discovery, an evaluation to justify continued operation of both Salem Units, concluded the present dropout setpoint of the relays does not meet the intent of the BTP. However, Revision 1 of Engineering Calculation ES-15.00S(Q) determined there is not a significant safety concern with the present dropout setpoint provided the 4.16KV vital buses are maintained at 4.3KV or greater. Design changes will be implemented during the next refueling outage on each Unit to change the dropout setpoint to meet the intent of the BTP. For the interim, 4.16KV vital bus voltages are being monitored to assure load tap changers are operating properly to maintain a minimum bus voltage of 4.3KV. In addition, bus voltages below 4.3KV will be adjusted between 4.3KV and 4.5KV and restrictions concerning vital bus lineup will be in effect (see "CORRECTIVE ACTIONS:" section).
Since 93.2% bus voltage is required to ensure the minimum motor terminal voltage, the existing 91. 6% dropout setpoint is not in compliance with the UFSAR or the BTP. However, because ES-15.00S(Q) calculations also show that vital bus recovery voltage will not degrade to a level at which actual motor degradation could occur, the intent of the UFSAR and BTP is still met. These calculations take credit for operation, prior to the event, of the load tap changers which are set to maintain a minimum initial bus.voltage of 4.3KV.
Analysis of this event is continuing..
Following *event discovery, an evaluation to justify continued operation of both Salem Units, concluded the present dropout setpoint of the relays does not meet the intent of the BTP. However, Revision 1 of Engineering Calculation ES-15.00S(Q) determined there is not a significant safety concern with the present dropout setpoint provided the 4.16KV vital buses are maintained at 4.3KV or greater. Design changes will be implemented during the next refueling outage on each Unit to change the dropout setpoint to meet the intent of the BTP.
Included will be a historical assessment of the effect of the revised assumptions at vital bus levels below 4KV. Upon completion of this effort, a supplement to this LER will be submitted.
For the interim, 4.16KV vital bus voltages are being monitored to assure load tap changers are operating properly to maintain a minimum bus voltage of 4.3KV. In addition, bus voltages below 4.3KV will be adjusted between 4.3KV and 4.5KV and restrictions concerning vital bus lineup will be in effect (see "CORRECTIVE ACTIONS:" section).
SUPPLEMENTAL LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station Unit 1 APPARENT CAUSE OF OCCURRENCE:
Analysis of this event is continuing.. Included will be a historical assessment of the effect of the revised assumptions at vital bus levels below 4KV. Upon completion of this effort, a supplement to this LER will be submitted.
DOCKET NUMBER 5000272 LER NUMBER 93-014-01 PAGE 4 of 5 The cause of this event is."Design, Manufacturing, Construction/Installation", per NUREG-1022  
 
*-The 91. 6% dropout setpoint was based on the lowest voltage the 4.16 KV motors could be allowed to operate (i.e. 90%) due to voltage drops in the motors' cables and relay inaccuracy considerations.
SUPPLEMENTAL LICENSEE EVENT REPORT (LER) TEXT CONTINUATION       l Salem Generating Station       DOCKET NUMBER     LER NUMBER       PAGE Unit 1                            5000272        93-014-01       4 of 5 APPARENT CAUSE OF OCCURRENCE:
The revised dropout setpoint, based upon the revised recovery voltage of 93.2%, will now maintain all motors operable under degraded voltage conditions.
The cause of this event is."Design, Manufacturing, Construction/Installation", per NUREG-1022 *- The 91. 6% dropout setpoint was based on the lowest voltage the 4.16 KV motors could be allowed to operate (i.e. 90%) due to voltage drops in the motors' cables and relay inaccuracy considerations. The revised dropout setpoint, based upon the revised recovery voltage of 93.2%, will now maintain all motors operable under degraded voltage conditions.
PRIOR SIMILAR OCCURRENCES:
PRIOR SIMILAR OCCURRENCES:
No prior similar occurrences of this event were identified.
No prior similar occurrences of this event were identified.
SAFETY SIGNIFICANCE:
SAFETY SIGNIFICANCE:
Engineering is currently completing its evaluation of the safety significance of past operation with the non-conservative second level UV setpoint.
Engineering is currently completing its evaluation of the safety significance of past operation with the non-conservative second level UV setpoint. With the current interim controls, the health and safety of the public.is not affected by this event. Upon completion of this evaluation this LER will be supplemented.
With the current interim controls, the health and safety of the public.is not affected by this event. Upon completion of this evaluation this LER will be supplemented.
CORRECTIVE ACTION:
CORRECTIVE ACTION: Design changes will be implemented to change the.relay setpoint on both Units to meet the requirements of BTP-PSB-1 and be in accordance with the plant design basis. This will be done during the upcoming Unit 1 refueling outage and the next Unit 2 refueling outage. A License Change Request will be implemented to revise Technical Specifications in accordance with the second level UV reiay setpoint concern. The UFSAR will be reviewed and revised as appropriate.
Design changes will be implemented to change the.relay setpoint on both Units to meet the requirements of BTP-PSB-1 and be in accordance with the plant design basis. This will be done during the upcoming Unit 1 refueling outage and the next Unit 2 refueling outage.
Administrative controls are being implemented to ensure the following restrictions are employed as interim action until implementation of design changes: 1.
A License Change Request will be implemented to revise Technical Specifications in accordance with the second level UV reiay setpoint concern.
* 4.16KV vital bus voltages will be logged hourly to assure a minimum vital bus voltage of 4.3KV. Bus voltages less than 4.3KV will be adjusted to between 4.3KV and 4.5KV. 2. Only two vital buses may be energized from their operating transformer if both the corresponding group buses are on their respective APT. 3a. Three vital*buses may be energized from the operatingtransf ormer if one of the corresponding group buses is transferred to the operating SPT or l 
The UFSAR will be reviewed and revised as appropriate.
*
Administrative controls are being implemented to ensure the following restrictions are employed as interim action until implementation of design changes:
* SUPPLEMENTAL LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating station Unit 1 CORRECTIVE ACTION: (cont'd) DOCKET NUMBER 5000272 LER NUMBER 93-014-01 PAGE 5 of 5 3b. Three vital buses may be energized from the operating transformer if the load which can be transferred from the APTs is reduced by 5 mega volt amps. MJPJ:pc SORC Mtg. 93-077 General Manager -Salem Operations}}
: 1.
* 4.16KV vital bus voltages will be logged hourly to assure a minimum vital bus voltage of 4.3KV. Bus voltages less than 4.3KV will be adjusted to between 4.3KV and 4.5KV.
: 2. Only two vital buses may be energized from their operating transformer if both the corresponding group buses are on their respective APT.
3a. Three vital*buses may be energized from the operatingtransf ormer if one of the corresponding group buses is transferred to the operating SPT or
 
SUPPLEMENTAL LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating station       DOCKET NUMBER     LER NUMBER       PAGE Unit 1                          5000272          93-014-01     5 of 5 CORRECTIVE ACTION:    (cont'd) 3b. Three vital buses may be energized from the operating transformer if the load which can be transferred from the APTs is reduced by 5 mega volt amps.
General Manager -
Salem Operations MJPJ:pc SORC Mtg. 93-077}}

Latest revision as of 06:07, 3 February 2020

LER 93-014-01:on 930722,concern Raised Re 4 Kv Vital Bus Second Level Undervoltage Protection Dropout Setpoint Due to Design,Mfg,Const/Installation.Analysis of Event Continuing. Suppl LER Will Be Submitted
ML18100A577
Person / Time
Site: Salem PSEG icon.png
Issue date: 08/27/1993
From: Pastva M
Public Service Enterprise Group
To:
Shared Package
ML18100A576 List:
References
LER-93-014-01, LER-93-14-1, NUDOCS 9309030259
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NRC FORM 366 U.S. NUCLEAR REGULATORY COMMISSION (6-89) APPROVEO OMB NO. 3150-0104 EXPIRES: 4/30/92 ESTIMATED BUROEN PER RESPONSE TO COMPLY WTH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. FORWARO LICENSEE EVENT REPORT (LER) COMMENTS REGAROING BUROEN ESTIMATE TO THE RECOR OS ANO REPORTS MANAGEMENT BRANCH (P-530), U.S. NUCLEAR REGULATORY COMMISSION, WASHINGTON, QC 20555, ANO TO THE PAPERWORK REOUCTION PROJECT 13150-0104). OFFICE OF MANAGEMENT ANO BUOGET, WASHINGTON, QC 20503.

FACILITY NAME 111 OOCKET NUMBER (2) I PAGE 131 Salem Generating Station - Unit 1 TITLE 141 I01s101010121112 1!0F01S 4KV Vital .Bus Second Level Undervoltage Protection Dropout Setpoint Concern (both Units).

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CAUSE SYSTEM COMPONENT TUR ER TUR ER I I I I I I I I I I I I I I I I I I I I I I I I I I I I SUPPLEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED SUBMISSION DATE 115l

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  • On 7/22/93, it was determined that the present 91.6% dropout setpoint for second level undervoltage (UV) protection of the 4 kilovolt .(KV) vital buses (both Salem Units), may not fully protect motors should the bus voltage degrade to less than 93.2% but greater than 91.6%. This is contrary to Branch Technical Position (BTP)-PSB-1 and the Updated Final Safety Analysis Report (UFSAR). However, engineering calculation shows, given the postulated worst case design basis event, vital bus recovery voltage will not degrade to less than 93.2%. The 91.6% dropout setpoint was based on the lowest voltage the 4.16 KV motors could be allowed to operate (i.e. 90%) due to voltage drops in the motors' cables and relay inaccuracy considerations. The revised recovery voltage of 93.2% will now maintain all motors operable under degraded voltage conditions.

During the next refueling outage on each Unit, design changes will be implemented to change the relay setpoint to meet the requirements of BTP-PSB-1. In the interim, administrative controls are being implemented. Technical Specifications and the UFSAR will be reviewed and revised as appropriate. Analysis of this event is continuing. Upon completion of this effort, a supplement to this LER will be submitted.

9309030259 930827 PDR ADOCK 05000272 I

NRC Form 366 (6-89)

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SUPPLEMENTAL LICENSEE EVENT REPORT (LER} TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE

  • unit 1 5000272 93-014-01 2 of 5 PLANT AND SYSTEM IDENTIFICATION:

Westinghouse - Pressurized Wate~ Reactor Energy Industry Identification System (EIIS} codes are identified in the text as {xx}

IDENTIFICATION OF OCCURRENCE:

4 KV Vitai Bus Second Level Undervoltage Protection Dropout Setpoint Concern (both Salem Units}

Event Discovery Date: 7/22/93 Supplement Report Date: 8/27/93 This report was initiated by Incident Report No.93-320. This event is reportable per 10CFR50.73(a} (2} (ii} (B} and 10CFR50.73(a} (2} (v} (D}.

CONDITIONS PRIOR TO OCCURRENCE:

Unit 1: Mode 1 Reactor Power 80% - Unit Load 815 MWe Unit 2: Mode 1 Reactor Power 100% - Unit Load 1140 MWe DESCRIPTION OF OCCURRENCE:

On July 22, 1993, it was determined that the present 91.6% dropout setpoint for second level undervoltage (UV} protection of the 4 kilovolt (KV} vital buses {VJ} (both Salem Units}, will not fully protect motors at the 230 and 460 volt level should the 4KV bus voltage degrade to less than 93.2% but greater than 91.6%. This is contrary to Branch Technical Position (BTP.}-PSB-1 and the Updated Final Safety Analysis.Report (UFSAR}. However, engineering calculation shows, given the postulated worst case design basis event, vital bus recovery voltage will not degrade to less than 93.2%.

The Nuclear Regulatory Commission was notified of this event per Code of Federal Regulations 10CFR50.72(b} (1) (ii) (B).

ANALYSIS OF OCCURRENCE:

Availability of minimum redundant alternating current (A.C.) power sources and distribution systems ensures sufficient power will be available to safety-related equipment for safe shutdown of the facility and the mitigation and control of accident conditions within the facility, as required by General Design Criteria 17 of Appendix "A" to 10CFR Part 50. Per BTP-PSB-1, the plant.licensing basis requires a second level of undervoltage protection for 4KV vital buses to ensure minimum motor terminal voltage for all safety-related

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. SUPPLEMENTAL LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit.1 5000272 93-014-01 3 of 5 ANALYSIS OF OCCURRENCE: (cont'd) motors. At Salem, when vital bus voltage drops below the dropout setpoint for relays providing this protection for greater than 13 seconds, vital bus loads are automatically transferred to their respective emergency diesel generators.

  • As part of the self-initiated Electrical Engineering Self-Assessment Program, electrical calculations are being reviewed to ensure guidelines of BTP-PSB-1 are met. On July 1, 1993, review of Revision 1 of ES-15.00S(Q), "Salem Units 1 and 2 Degraded Grid study" identified a potential concern with the 91.6% dropout setpoint of the Units' 4KV vital buses (lA, lB, lC, 2A, 2B, and 2C). on
  • July 22, 1993, further analysis of this concern determined the recovery vital bus voltage is 93.2% of 4.16KV following transfer of the Auxiliary Power Transformers (APTs) to the Station Power
  • Transformers (SPTs). This voltage could result should a group bus transfer to the SPTs occur coincident with a Loss-of-Coolant Accident (LOCA) and the unaffected unit in startup or shutdown.

UFSAR Section 8.3.1.2 describes the setpoint as being determined using the 90% minimum motor terminal voltage as the starting point.

Since 93.2% bus voltage is required to ensure the minimum motor terminal voltage, the existing 91. 6% dropout setpoint is not in compliance with the UFSAR or the BTP. However, because ES-15.00S(Q) calculations also show that vital bus recovery voltage will not degrade to a level at which actual motor degradation could occur, the intent of the UFSAR and BTP is still met. These calculations take credit for operation, prior to the event, of the load tap changers which are set to maintain a minimum initial bus.voltage of 4.3KV.

Following *event discovery, an evaluation to justify continued operation of both Salem Units, concluded the present dropout setpoint of the relays does not meet the intent of the BTP. However, Revision 1 of Engineering Calculation ES-15.00S(Q) determined there is not a significant safety concern with the present dropout setpoint provided the 4.16KV vital buses are maintained at 4.3KV or greater. Design changes will be implemented during the next refueling outage on each Unit to change the dropout setpoint to meet the intent of the BTP.

For the interim, 4.16KV vital bus voltages are being monitored to assure load tap changers are operating properly to maintain a minimum bus voltage of 4.3KV. In addition, bus voltages below 4.3KV will be adjusted between 4.3KV and 4.5KV and restrictions concerning vital bus lineup will be in effect (see "CORRECTIVE ACTIONS:" section).

Analysis of this event is continuing.. Included will be a historical assessment of the effect of the revised assumptions at vital bus levels below 4KV. Upon completion of this effort, a supplement to this LER will be submitted.

SUPPLEMENTAL LICENSEE EVENT REPORT (LER) TEXT CONTINUATION l Salem Generating Station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-014-01 4 of 5 APPARENT CAUSE OF OCCURRENCE:

The cause of this event is."Design, Manufacturing, Construction/Installation", per NUREG-1022 *- The 91. 6% dropout setpoint was based on the lowest voltage the 4.16 KV motors could be allowed to operate (i.e. 90%) due to voltage drops in the motors' cables and relay inaccuracy considerations. The revised dropout setpoint, based upon the revised recovery voltage of 93.2%, will now maintain all motors operable under degraded voltage conditions.

PRIOR SIMILAR OCCURRENCES:

No prior similar occurrences of this event were identified.

SAFETY SIGNIFICANCE:

Engineering is currently completing its evaluation of the safety significance of past operation with the non-conservative second level UV setpoint. With the current interim controls, the health and safety of the public.is not affected by this event. Upon completion of this evaluation this LER will be supplemented.

CORRECTIVE ACTION:

Design changes will be implemented to change the.relay setpoint on both Units to meet the requirements of BTP-PSB-1 and be in accordance with the plant design basis. This will be done during the upcoming Unit 1 refueling outage and the next Unit 2 refueling outage.

A License Change Request will be implemented to revise Technical Specifications in accordance with the second level UV reiay setpoint concern.

The UFSAR will be reviewed and revised as appropriate.

Administrative controls are being implemented to ensure the following restrictions are employed as interim action until implementation of design changes:

1.
  • 4.16KV vital bus voltages will be logged hourly to assure a minimum vital bus voltage of 4.3KV. Bus voltages less than 4.3KV will be adjusted to between 4.3KV and 4.5KV.
2. Only two vital buses may be energized from their operating transformer if both the corresponding group buses are on their respective APT.

3a. Three vital*buses may be energized from the operatingtransf ormer if one of the corresponding group buses is transferred to the operating SPT or

SUPPLEMENTAL LICENSEE EVENT REPORT (LER) TEXT CONTINUATION Salem Generating station DOCKET NUMBER LER NUMBER PAGE Unit 1 5000272 93-014-01 5 of 5 CORRECTIVE ACTION: (cont'd) 3b. Three vital buses may be energized from the operating transformer if the load which can be transferred from the APTs is reduced by 5 mega volt amps.

General Manager -

Salem Operations MJPJ:pc SORC Mtg.93-077

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