05000266/LER-1993-007

LER 93-007-00:on 930726,EDG Inadvertently Started and Station Battery Tripped Off Due to Undervoltage Signal. Caused by Blown Fuse as Result of Human Error During Calibr of 1A-06 Voltmeter.Fuse replaced.W/930825 Ltr

ML20056F870
Person / Time
Site:	Point Beach
Issue date:	08/25/1993
From:	Castell C, Link B WISCONSIN ELECTRIC POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-93-092, CON-NRC-93-92 LER-93-007, LER-93-7, VPNPD-93-145, NUDOCS 9308310241
Download: ML20056F870 (6)

LER-2093-007,

Event date:
Report date:
2662093007R00 - NRC Website

text

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\ Electnc POWER COMPANY 231 w Michom. Po to 2046. Mwouvea wl 53205 M44) 2212M5 VPNPD-93-145 NRC-93-092 August 25, 1993 Document Control Desk U.S. NUCLEAR REGULATORY COMMISSION

j. Mail Station P1-137 l Washington, DC 20555 Gentlemen:

DOCKETS 50-266 AND 50-301 LICENSEE EVENT REPORT 93-007-00 INADVERTENT EMERGENCY DIESEL START AND LOSS OF A STATION BATTERY CHARGER POINT BEACH NUCLEAR PLANT, UNITS 1 AND 2 Enclosed.is Licensee Event Report 93-007-00 for Point Beach Nuclear Plant, Units 1 and 2. This report is being submitted in accordance with the requirements of 10 CFR 50.73 (a) (2) (i) (B) , "Any operation or condition prohibited by the plant's Technical Specifications," and 10 CFR 50.73 (a) (2) (iv) , "Any event or condition that resulted in a }

manual or automatic actuation of any Engineered Safety Feature (ESF),

including the reactor protection system (RPS)." This report describes a situation that caused a blown fuse in the metering and-relaying circuit for the 1A-06 4160 Volt emergency. bus.

Please contact us if there are any questions.

Sincerely, h Y Bob LJ

-Vice President Nuclear Power l

CAC/jg l_

Enclosure cc: NRC Resident Inspector NRC Regional Administrator, Region III

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9308310241 930825 m[g6 ;. /

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l NRC FORQ 366 U.S. NUCLEAR REBJLAT(DY CDPMISS!(O APPROVED BY UMB CD. 3150-0104 I(5-92) EXPIRES 5/31/95 ESilMATED BURDEN PER RESPONSE TO COMPLY WITH l THIS INFORMATION COLLECTION REQUEST: 50.0 HRS. '

LICENSEE EVENT REPORT (LER) FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO  !

THE IkFORMATION AND RECORDS MANAGEMENT BRANCH ,

(MNBB 7714), U.S. NUCLEAR REGULATORY COMMIS$10N, i (See reverse for required nuntier of digits / characters for each block) WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK j REDUCT!DN PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET WASHINGTON, DC 20503.

FCCILITY RAME (1) DOCKET KMBER (2) PAGE (3)

POINT BEACH NUCLEAR PLANT, UNIT 1 , 05000266 1 OF 5 TITLE (4)

INADVERTENT EMERGENCY DIESEL START AND LOSS OF A STATION BATTERY CHARGER  ;

EVf WT DATE (5) (ER NLMBIR (6) REPORT DATE (7) OTHER FAClllTIES INVOLVED (8)  !

SEQUENTIAL REVISION FACILITY KAME DOCKET NUMBER MONTH DAY YEAR YEAR NUMBER NUMBER MONTH DAY MAR PBNP UNIT 2 05000301 l 07 26 93 93 -- 007 -- 00 08 25 93

'# ' ' "#" i 05000 i OPERATING N

'"'* "*" "' ' ' ' ' " ' " ' " ' """*"*"' ' '"' "' "'"I"8 " h"'" "* ' " " ' ' ' ' " '

C3DE (9) 20.402(b) 20.405(c) X $0.73(a)(2)(iv) 73.71(b)

POWER 20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.71(c) l LEVEL (10) 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) OTHER r 20.405(a)(1)(iii) X 50. 73(a)(2)(i ) 50.73(a)(2)(viii)(A) (Specify in t 20.405(a)(1)(iv) * ' "

50.73(a)(2)( t i ) 50.73(a)(2)(viii)(B) 20.405(a)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x) NRC Form 366A) llCE NSEE CtwTACT FOR THIS LFR (12)

AAME TELEPHONE h'>MEER (Include Area Code)

CURTIS A. CASTELL, SENIOR ENGINEER-LICENSING 414-221-2019 l

i COMPLETE ONE LINE FOR EACH COMPONENT FAltuRE DESCRIBED IN THIS REPORT (15)

CAUSE SYSTEM COMPONENT MANUFACTURER CAUSE SYSTEM COMPONENT MANUFACTURER 0 P A EF FU X999 N SUPPLEMENT AL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR Y SUBMISSION X (ES If yes, conplete EXPECTED SULMISSION DATE). "O 10 25 93 DATE (15)

ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16) I On July 26, 1993 at about 1333 hours0.0154 days <br />0.37 hours <br />0.0022 weeks <br />5.072065e-4 months <br />, with both units at full power, a fuse [

in the Unit 1, B train, 4160V emergency bus 1A-06 metering and relaying  :

circuit blew during calibration of the 1A-06 voltmeter. The blown fuse caused a IA-06 undervoltage signal to be generated. The undervoltage i signal caused the normal power supply breaker for 1A-06 to open and deenergize the bus. The emergency diesel generator G-02 immediately started and reenergized the 1A-06 bus. One of thd four station battery  !

chargers (D-108) tripped off, as designed, during the momentary loss of power to the Unit 1, B train. Technical Specification 15.3.7.A.1.h requires a battery charger to be in operation to each of the four DC buses. l If this condition is not met, Technical Specification 15.3.0 states that the units must be in Hot Shutdown within 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. D-108 was restored at 1355 hours0.0157 days <br />0.376 hours <br />0.00224 weeks <br />5.155775e-4 months <br />, which ended the Technical Specification 15.3.0, 3-hour limiting  ;

condition for operation. The DC buses for PBNP are shared by both units, '

therefore, this LCO was applicable to both units. Normal configuration of l the other equipment that was affected was re-established. The blown fuse was replaced at about 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> and the normal configuration of the electrical distribution system was re-established at 1443 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.490615e-4 months <br />. The blown fuse was caused by human error during calibration of the 1A-06 voltmeter. l l

hRC f0kM 366 (5-92) l

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NRC FORR 366A U.S. CUCLEAR REGLILATOY COWIISSIC APPROVED BY OMB NO. 3150-0104 45-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO LICENSEE EVENT REPORT (LER) THE isFoRMATioN Aho RECORDS MANAGEMENT ERANCH i TEXT CONTINUATION (MNBB 7714), U.S. NUCLEAR REGULATORY COMMIS$10N, WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMf WT AND BLOGET, WA$N]NGTON, DC 20503.

FACILITY NAME (1) DOCKET NtMPER (2) LFR MLMIER (6? PAGF (3)

YEAR SEQUENTIAL REVISION POINT BEACH NUCLEAR PLANT 05000266 "" ""

93 2 OF 5

-- 0 0 7 -- 00 TEXT (If more space is recuired, use additional copies of NRC Form 366A) (17)

EVENT DESCRIPTION On July 26, 1993, at about 1333 hours0.0154 days <br />0.37 hours <br />0.0022 weeks <br />5.072065e-4 months <br />, with both units at full power, a fuse in the Unit 1, B train, 4160V emergency bus 1A-06 metering and relaying circuit blew during calibration of the IA-06 voltmeter. The ,

blown fuse caused a 1A-06 undervoltage signal to be generated because the voltmeter is in the same circuit as the undervoltage protection relays.

The undervoltage signal caused the normal power supply breaker for 1A-06 ,

to open and deenergize the bus. The emergency diesel generator G-02 immediately started and reenergized the 1A-06 bus. '

Other equipment affects due to the momentary loss of voltage on the 1A-06 bus included:

Battery Charger D-108 tripped 1A-06 voltmeter and synchronization circuitry were lost due to the blown fuse ,

Charging Pump P-002C tripped due to the undervoltage $

Letdown Isolation occurred due to the undervoltage i Motor Control Center B-43 feeder breaker 1B52-21C tripped due to the undervoltage The B train Service Water Pumps were sequenced on due to the undervoltage and restoration of voltage by the emergency diesel i generator j l

Normal configuration of this equipment was re-established. The blown i fuse was replaced at about 1430 hours0.0166 days <br />0.397 hours <br />0.00236 weeks <br />5.44115e-4 months <br /> and the normal configuration of the j electrical distribution system was re-established at 1443 hours0.0167 days <br />0.401 hours <br />0.00239 weeks <br />5.490615e-4 months <br />.  ;

1 Technical Specification 15.3.7.A.1.h states, "Four battery chargers are operable with one charger carrying the DC loads on each main DC distribution bus: D01, D02, D03, and D04." The battery charger D-108 is the normal battery charger for D04. Technical Specification 15.3.0 was applicable for this situation, because Technical Specification 15.3.7.A.1.h does not provide a limiting condition of operation (LCO) action statement for operation with less than 4 battery chargers.

Battery Charger D-108 was restored at 1355 hours0.0157 days <br />0.376 hours <br />0.00224 weeks <br />5.155775e-4 months <br /> and the Technical )

Specification 15.3.0 3-hour limiting condition for operation was exited. '

The DC buses for PBNP are shared by both units, therefore, this LCO was applicable to both units.

The IA-06 voltmeter was being calibrated when the fuse blew. The calibration was being performed by two electricians, one from Point Beach ^

and one from the Electrical Testing and Maintenance division of the N3C FORM 366A (5-92)

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NRC FORM 366A U.S. C33 CLEAR REGAATOY CupMIS$10 APPRCNED BY OMB NO. 3150-0104

<5-92) EkPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS lhFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO LICENSEE EVENT REPORT (LER) THE Inr0RMATION AND RECORDS MANAGEMENT SP.ANCH TEXT CONTINUATION (MhBB 7714), U.S. NUCLEAR REGULATORY COMMIS$10N, WASHINGTON, DC 20555-0001, AND TO THE PAPERWDRK j REDUCTION FROJECT (3150-0104), OFFICE OF MAN AGEMENT AND BUDCET, WASHINGTON DC 2D503.

F ACIllTY NAME (1) DTIET mmBER (?) LER E mftER (65 PAM (3)

SEQUE NTI AL REVISION YEAR POINT BEACH NUCLEAR PLANT 05000266 93 3 OF 5

-- 0 0 7 -- 00 TEXT (If more space is reavired. use additional cooles of hkC form M6A) (17)

System Operations Department of Wisconsin Electric. The written instruction being used was Preventive Maintenance Task Sheet 0048015.

The 1A-06 voltmeter that was being calibrated is located in the control room on control panel C-02. The instruction requires two sliders to be opened to electrically isolate the 1A-06 voltmeter from the 1A-06  ;

undervoltage protection relays while the voltmeter is being calibrated.

The isolation of the voltmeter and connection of the calibration [

equipment is performed inside contrcl panel C-02.

At about 1330 hours0.0154 days <br />0.369 hours <br />0.0022 weeks <br />5.06065e-4 months <br />, one electrician opened sliders WNA-8 and WNA-9 on Riser 33 inside C-02 to isolate the voltmeter. The other electrician verified that the 1A-06 voltmeter was at 0 volts. This verification showed that the proper voltmeter was being isolated. This is not a complete verification of the slider position however, because the voltmeter would read 0 volts if only one slider is open.

A visible electrical arc appeared when the electrician attempted to connect the test instrument to the isolated side of slider WNA-9. The electrician immediately suspected that he had created a short circuit and that a fuse had blown in the circuitry. He immediately informed the Duty ,

Shift Superintendent. Electrical Maintenance and Engineering personnel ,

diagnosed and replaced the blown fuse.

It is believed that one of the sliders was not opened completely to isolate the circuit. A Human Performance Evaluation was chartered to determine causes and corrective actions for this event.

CAUSES Initial results from the Human Performance Evaluation indicate that this event was caused by a human error by one of the electricians performing calibration of the 1A-06 voltmeter. A contributing factor to this error l was lack of verification of both sliders being open. '

CORRECTIVE ACTIONS i The task sheet instruction for performing the calibration has been changed to perform verification of the slider positions.

About three days after the above described event, a similar situation ,

occurred which caused a voltage perturbation on a vital instrument bus. l This subsequent event was not reportable, but it was an indication that the above corrective action may not be adequate to preclude similar events. The Human Performance Evaluation was expanded to include kRC FORM 366A (5-92)

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1 WRC FORN 366A U.S. NUCLEAR REQJLATOY (DmlESIO APODVED BY CMB NO. 3150-0104 (5-92) EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS IkFORMATION COLLECTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDlWG BURDEN ESTIMATE TO LICENSEE EVENT REPORT (LER) THE INFORMATION AND RECORDS MANAGEMENT BRANCH TEXT CONTINUATION (MNBB TM4), U.S. NUCLEAR REGULATORY COMMIS$10N, l WASHINGTON, DC 20555-0001, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104), OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.

FACILITY NAME (1) DOCKET NUMBER (2) LER NtMBER (6? PAGE (3)

SEQUENTIAL REVISION YEAR POINT BEACH NUCLEAR PLANT "" """

05000266 93 00 4 OF 5

-- 007 --

l l TEKI (If trere space is required, use exitional copies of ARC Form 366A) (IT) evaluation of the subsequent event. A supplemental Licensee Event Report will be provided when the corrective actions from the Human Performance Evaluation are finalized. l l

COMPONENT AND SYSTEM DESCRIPTION l

The 1A-06 emergency bus provides power for train "A" safety-related and some non-safety-related equipment. The undervoltage protection and metering circuitry for the 1A-06 bus are used to monitor voltage on the 1A-06 bus and provide initiation of the undervoltage protection which includes automatic disconnection of the bus from off-site power and restoration of power by the emergency diesel generator. The undervoltage l protection and metering circuitry are powered from potential transformers (PT) on the IA-06 bus. The secondaries of these PT circuits are protected by 6 amp fuses.

Various loads automatically trip on undervoltage. The Unit 1 B train loads that tripped during this event were: Station Battery Charger D-108, Charging Pump 1P-002C, and Motor Control Center B-43. Some ,

safety-related equipment is automatically started by sequencing circuitry I following restoration of power to the bus. Service water pumps P-032C, P-032D, and P-032E all started automatically by the sequencing circuitry.

The loss of voltage to the letdown isolation valve IRC-00427 caused reactor coolant letdown isolation.

The IEEE Standard 803A-1983 component identifiers for this report are:

l Bus BU l Voltmeter EI Undervoltage Relay 27 Fuse FU REPORTABILITY This Licensee Event Report is provided pursuant to the requirements of 10 CFR 50.73 (a) (2) (i) (B) , "Any operation or condition prohibited by the plant's Technical Specifications" and 10 CFR 50.73 (a) (2) (iv) , "Any event or condition that resulted in manual or automatic actuation of any Engineered Safety Feature (ESP), including the Reactor Protection System (RPS) . " A four-hour notification to the NRC was made at 1453 hours0.0168 days <br />0.404 hours <br />0.0024 weeks <br />5.528665e-4 months <br /> in accordance with 10 CFR 50.72 (b) (2) (ii) , "Any event or condition that results in manual or automatic actuation of any Engineered Safety Feature (ESF), including the Reactor Protection System (RPS)."

Cf!C 70RM 366A (5-92) l l

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380. 3150-0104 s . , APPROVED BY OMSEXPIRES 5/31/95 U.S. WJCLEAR REGULATORY BURDEN CDMISSIONf PER RESPONSE REQUEST: 50,0 HRS. TO COMPL ESTIMATED COLLECTION ESTIMTE To CRC FORN 366A THIS t$-92) FORWARD thFORMATION COMMENTS REGARDING BURDENMANAGEMENT BR RECORDS ATORY COMMIS$10N, THE rwfoR m T10w AwD (LER) (Mwas m4), U.S. WUCLEAR REGULAND OFFICE OF TO THE PAPERWO DC 20555-0001,(3150-0104),

kASHlWGTOW, PROJECT j

J LICENSEE EVENT REPORT j MANAGEMENT AND 1 BUDGET , WASHIN REDUCTION TEXT CONTINUATION PAGF (37 tra utmsta (6}

nottET w+mre (?; p YEAR f SEQUENTIAL N 5 OF 5 "M [ REVISION JACniTY mAur (17 00 05000266 93 - 007 I POINT BEACH NUCLEAR PLANT (17) dditional copies of ARC f orm 3t4A) 7 TExi (11 Pete space is reqaired, use e

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d the SAFETY ASSESSMENT generated by the blown fuse causeThe automa -

i The undervoltage signal that wasprotection for and 1A-06.the sequencing restoration of the of power t actuation of the undervoltage G-02, f disconnection from the normal power source, f power to '

l the bus by the emergency diesel generator l water pumps functioned proper y.d by the momentary inte service The equipment that was affectetrain was restored in a shor emergency bus "B" the Unit safety 1 the D-108 adverse effects. mally continuously charged byh rger caused The D-106 station battery is norThe loss of the D-108 battery The c aThe st station battery charger. begin discharging. loads for one hour. Tables 8.2-1 and the D-106 station battery tocarrytthe red maximum in 22 expected DC ed after minutes.

battery charger for D-106 was tres faresizedto theobattery charger is restor i d of Coolant Accident which isthe DC battery 8.2-2 of the PBNP FSAR Therefore,show thathe injection phase of th approximately one half hour.

operable during this event. i I

SIMILAR OCCURRENCES: describe the inadvertent actuat on he following Licensee Event Reports an Engineered Safety Feature:

1 1 or_ common i sel Generator i sel Generator Due to

-006 Inadvertent Start of Emergency D eInadverte 003 Personnel Error i sel Generator i sel Generator Inadvertent Start gency of Emergency Diesel Generatoras D eInadverte a Resu Inadvertent Start of Emer

-Inadvertent ESF Actuation turveillance Testing

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-i NRC FORM 366A U.S. trJCLEAR RE(KJLATORY CasMISSl(O APPROVED I;T Ops CD. 3150-0104 15-92) EXP!RES 5/31/95 ESTIMATED BURDEN PER RE!,PONSE TO COMPLY WITH

, THl$ INFORMAT!ON COLLE CTION REQUEST: 50.0 HRS.

FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO LICENSEE EVENT REPORT (LER) THE lhFORMATION AND RECORDS MANAGEMENT BRANCH TEXT CONTINUATION (MWB8 771'), U.S. NUCLEAR REGULATORY COMMIS$10N, WASHINGTON, DC 20555-0001, AND TO THE PAPERWOM REDUCTION PROJECT (3150-0104), OFFICE OF MANAGFMENT AND BUDGET, WASHINGTON, DC 20503.

FAttlITY MAMF (1) DOCKFT tRMBER (?) LER tRMRER (6? PAGE (3)

YEAR SEQUENTIAL RtVISION POINT BEACH NUCLEAR PLANT *" """

05000266 93 5 OF 5

__"007 __ 00 TEXT (11 more space is recruired, use additional copies cf NRC form 366A) (17)

SAFETY ASSESSMENT The undervoltage signal that was generated by the blown fuse caused the actuation of the undervoltage protection for 1A-06. The automatic disconnection from the normal power source, the restoration of power to the bus by the emergency diesel generator G-02, and sequencing of the service water pumps functioned properly.

The equipment that was affected by the momentary interruption of power to the Unit 1 emergency bus "B" train was restored in a short time with no adverse safety effects.

1 The D-106 station battery is normally continuously charged by the D-108 station battery charger. The loss of the D-108 battery charger caused the D-106 station battery to begin discharging. The station batteries are sized to carry the maximum expected DC loads for one hour. The battery charger for D-106 was restored in 22 minutes. Tables 8.2-1 and 8.2-2 of the PBNP FSAR show that the battery charger is restored after the injection phase of the Loss of Coolant Accident which is approximately one half hour. Therefore, the DC battery system remained operable during this event.

SIMILAR OCCURRENCES:

The following Licensee Event Reports describe the inadvertent actuation of an Engineered Safety Teature:

Unit 1 or common LER 91-006 Inadvertent Start of Emergency Diesel Generator '

LER 92-003 Inadvertent Start of Emergency Diesel Generator Due to Personnel Error Unit 2 i

LER 84-005 Inadvertent Start of Emergency Diesel Generator LER 84-006 Inadvertent Start of Emergency Diesel Generator i LER 84-007 Inadvertent Start of Emergency Diesel Generator l LER 92-007 Inadvertent ESF Actuation as a Result of Improper Surveillance Testing i

NRC FORM 366A (5-92)

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