05000331/LER-1995-001, :on 950128,both stand-by DGs Automatically Started.Caused by Sensed Momentary under-voltage Condition on Both Essential Buses.Operators Verified That Essential Buses Being Powered from Normal Source
| ML20080J696 | |
| Person / Time | |
|---|---|
| Site: | Duane Arnold  |
| Issue date: | 02/17/1995 |
| From: | Klotz B, Denise Wilson IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT |
| To: | Martin J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| References | |
| LER-95-001, LER-95-1, NG-95-0506, NG-95-506, NUDOCS 9502280050 | |
| Download: ML20080J696 (5) | |
| Event date: | |
|---|---|
| Report date: | |
| Reporting criterion: | 10 CFR 50.73(a)(2)(iv), System Actuation 10 CFR 50.73(a)(2)(vii), Common Cause Inoperability 10 CFR 50.73(a)(2)(i) 10 CFR 50.73(a)(2) 10 CFR 50.73(a)(2)(viii) 10 CFR 50.73(a)(2)(x) |
| 3311995001R00 - NRC Website | |
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.y IES UTILITIES INC.
Febmary 17,1995 NG-95-0506 i
Mr. John B. Manin Regional Administrator Region III U. S. Nuclear Regulatory Commission 801 Warrenville Rosd Lisle, IL 60532 Subject: Duane Arnold Energy Center Docket No: 50-331 Op. License No: DPR-49 Licensee Event Report #95-001 File:
A-ll8a i
Gentlemen:
In accordance with 10 CFR 50.73 please find attached a copy of the subject Licensee Event Report.
i Very truly yours,,
David L. Wilson Plant Superintendent - Nuclear i
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DLW/BKAntun nierdethr. doe f
cc:
Director of Nuclear Reactor Regulation l
Document Control Desk U. S. Nuclear Regulatory Commission Mail Station PI-37
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Washington, D. C. 20555-0001
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NRC Resident inspector - DAEC c
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9502280050 950217 PDR ADOCK 05000331 S
PDR Duane Arnold Energy Center
- 3277 DAEC Road
- Palo. Iowa 52324
- 319/851-7611
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g An IES INDUSTRIES Company j
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i NRC FORM 366 U.S. NUCLEAR REGULATORY COMMIS$10N APPROVED BY OMB NO. 3150-0104 I
(5 92)
EXPIRES 5/39/05 ESTIMATED BURDEN PER RESPONSE TO COMPLT,WITH THIS LICENSEE EVENT REPORT (LER)
INFORMATION COLLECTION REQUEST:
50.0 HRS.
FOPWARD COMMENTS REGARDING BURDEN ESTIMLTE TO THE IN FORMATIOL.' AND RECORCS ttANACEMENT EPANCH (MNBB
{
(See reverse for required number of digits / characters for each block)
W l GT DC 20 55 0001, A D T THE ER REDUCTION PROJECT (3150-0104),
OFFICE OF l
MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.
FACILITY NAME (1)
DOCKET NUMBER (2) l PAGE (3)
Duane Arnold Energy Center 05000-331 l
1 OF 4 I
IITLE (4)
Automatic Diesel Generator Start Due To Momentary Essential Bus Undervoltage EVE WT DATE (5)
LER NUMBER (6)
REPORT DATE (7)
OTHER FACILITIES INVOLVED (8)
MONTH DAY YEAR YEAR SEQUENTIAL REVISION MONTH DAY YEAR FACILITY NAME DOCKET NUMBER NUMBER NUMBER 01 28 95 95
-- 001 --
00 02 17 95 FACILITY NAME DOCKET NUMBER I
05000 OPERATING 1
THIS REPt"tf IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR 6: (Check one or more) (11) 20.402(b) 20.405(c)
X 50.73(a)(2)(iv) 73.71(b)
POWER 100 20.405(a)(1)(i) 50.36(c)(1) 50.73(alf2)(v) 73.71(c) 20.405(a)(1)(li) 50.36(c)(2) 50.73(a)(2)(vii)
OTHER 20.405(a)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2)(vii()(A)
(Specify in Abstract i
L, 20.405(a)(1)(1v) 50.73(a)(2)(i1) 50.73(a)(2)(viii)(B>
below and in Text, NRC v
f
?^
20.405(a)(1)(v) 50.73(a)(R)( t i i) 50.73(a)(2)(x)
Form 366a)
LICENSEE CONTACT FOR THIS LER (12)
NAME TELEPHONE NUMBER (Include Area Code)
Bruce Klotz, Principal Licensing Specialist (319) 851-7599 COMPLETE ONE LINE FOR EACH COMPONENT Fall.URE DESCRIBED IN THIS REPORT (13)
CAUSE
SYSTEM COMPONENT MANUFACTURER REPORTABLE
CAUSE
SYSTEM COMPONENT MANUFACTURER REPORTABLE TO NPRDS TO NPRDS SUPPLEMENTAL REPORT EXPECTED (14)
EXPECTED MONTH DAY YEAR VES
)c NO (If yes, complete EXPECTED SUBMIS$!ON DATE).
ABSTRACT (Limit to 1400 spaces, i.e., approximately 15 single-spaced typewritten lines) (16)
On January 28, 1995, with the plant operating at 100% power, both t
Standby Diesel Generators (SBDGs) automatically started but were not i
required to load.
i The cause of the automatic start was a sensed momentary under-voltage condition on both essential buses which was monitored i
by bus under-voltage relays that feed the SBDG start logics.
The sensed momentary under-voltage condition was caused by momentary grid disturbances following an ice storm.
Following verification that the essential buses were being powered from their normal source, the SBDGs were secured and returned to the standby mode.
This event had no effect on the safe operation of the plant.
9U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB NO. 3150-0104 I
EXPIIES 5/31/95 ESilMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REOUEST:
50.0 HRS.
LICENSEE EVENT REPORT (LER)
FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE TEXT CONTINUATION INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714),
U.S.
NUCLEAR REGULATORY COMMISSION, WASH]NGTON, DC 20555 0031, AND TO THE PAPERWORK REDUCTION PROJECT (3150-0104),
OFFICE OF MANAGEMENT AND BUDGET, WASHINGTON, DC 20503.
FACILITY NAME (1)
DOCKET NUMBER (2)
LER NUMBER (6?
PAGE (3)
YEAR SEQUENTIAL REVISION NUMBER NUMBER Duane Arnold Energy Center 05000-331 95
- - 0 01 - - 00 2 OF 4 TEXT (if more space is required, use additional copies of NRC Form 366A) (17)
I.
DESCRIPTION OF EVENT
At approximately 0100 on January 28, 1995, the plant was operating at 100% power and was in day 4 of a 14 day Limiting Condition for Operation (LCO) on the High Pressure Coolant Injection (HPCI)
System and in day 5 of a 30 day Administ cative LCO on the "A" Control Building Chiller.
The essential buses were being powered by the Startup transformer with the Standby transformer in backup (normal alignment).
A recent storm in the area had caused significant ice buildup on transmission lines in the electrical transmission system.
At 0108, two of the three phases (lines) of a 161Kv line located approximately 5.6 miles south of the Duane Arnold Energy Center (DAEC) switchyard came in contact with each other and caused a phase-to-phase fault.
The lines had been set in motion (galloping condition) by the ice buildup and the prevailing winds.
The fault was sensed by various protective relays and the line automatically isolated by the opening of two feeder breakers in the DAEC switchyard.
The breakers automatically re-closed 2 seconds later,
)
sensed that the fault still existed and tripped open.
The j
duration of each fault was about 45 msec (app. 3 cycles) with a fault current of 2500 amps.
A fault model showed that the voltage i
on the 161Kv bus in the DAEC switchyard dropped to approximately 65% of nominal voltage on two of the phases.with the third staying near normal.
The Standby Diesel Generator (SBDG) Bus under voltage relays sensed a decreased voltage on the essential buses.
As designed, both SBDGs started without sequencing to the buses.
Under-voltage alarms were received as expected on the Standby transformer and Instrument AC.
The voltage dip caused the Reactor Protection System (RPS) " alternate" Electrical Protection Assembly breaker to trip.
This voltage dip also caused the "B" Reactor Water Cleanup (RWCU) Pump and the "D" Well Pump to trip.
Both of these pumps have solid state controllers which are sensitive to voltage transients.
NRC 70RM,366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB No. 3150-0104 h"' I EXPIRES 5/~,1/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST:
50.0 HRS.
LICENSEE EVENT REPORT (LER)
FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE TEXT CONTINUATION INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714),
U.S.
NUCLEAR REGULATORY COMMISSION, WASH]NGTON, 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 NUMBER (6:
PAGE (3)
YEAR SEQUENTIAL REVISION NUMBER NUMBER Duane Arnold Energy Center 05000-331 95
- - 0 01 - - 00 3 OF 4 TEXT (if more space is required, use additional copies of NRC form 366A) (17)
At 0110, the "D" Well Pump was restored.
At 0129, the operating crew secured the SBDGs and returned them to the standby mode.
The two feeder breakers in the DAEC switchyard were reset at 0139.
At 0245, the RPS " alternate" EPA breaker was reset per procedure.
II. CAUSE OF EVENT
The cause of the automatic start of the SBDGs was a sensed momentary under-voltage condition on both essential buses which are monitored by bus under-voltage relays.
The relays feed directly into the SBDG start logics which seal in upon actuation.
The sensed momentary under-voltage conditions were also the causes for the RWCU and well water pump trips, the RPS " alternate" EPA breaker trip, and the alarms received.
The momentary under-voltage conditions were caused by the momentary grid disturbance.
III. ANALYSIS OF EVENT
This event had no effect on safe operation of the plant, nor would it have had an effect on safe operation during any other plant conditions.
The SBDGs started as designed in response to the sensed momentary voltage dips on the essential buses, but were not required to load.
When voltage drops to 65% of nominal on both the Startup and Standby transformers, the SB.DGs automatically start.
After the SBDGs reach rated frequency and voltage (10 seconds or less), they will pick up the essential busses if there is no voltage present.
Since the duration of the event was so short (less than 3 seconds), the essential busses had returned to nominal voltage by the time the SBDGs came up to speed.
The " alternate" EPA breaker was not feeding the Reactor Protection System at the time of the event, so consequently had no effect on the plant.
If the breaker had been in service at the time, a reactor half-scram would have resulted.
+
NaC 366A U.S. NUCLEAR REGULATORY COMMISSION APPROVED BY OMB No. 3150-0104 EXPIRES 5/31/95 ESTIMATED BURDEN PER RESPONSE TO COMPLY WITH THIS INFORMATION COLLECTION REQUEST:
50.0 HRS.
LICENSEE EVENT REPORT (LER)
FORWARD COMMENTS REGARDING BURDEN ESTIMATE TO THE TEXT CONTINUATION INFORMATION AND RECORDS MANAGEMENT BRANCH (MNBB 7714),
U.S.
NUCLEAR REGULATORY COMMIS$10N, 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 NUMBER (6:
PAGE (3)
YEAR SEQUENTIAL REVISION NUMBER NUMBER Duane Arnold Energy Center 05000-331 95
-- 001 -- 00 4 OF 4 TEXT (If more space is required, use additional copies of NRC Form 366A) (17)
The RWCU and well water systems are not safety related and tripping of these pumps had no adverse consequences.
There were no bus transfers or load sheds during these events.
All alarms and auto actuations that were received were expected.
IV.
CORRECTIVE ACTIONS
Following the SBDG start, operators verified that the essential buses were being powered from their normal cource and contacted the load dispatcher to share information and coordinate actions.
The SBDGs were secured, one at a time, after verifying that the grid was stable.
Operators took appropriate actions to restore the RWCU and well water systems.
All equipment operated properly and personnel actions were appropriate, no further corrective actions were required.
i V.
ADDITIONAL INFORMATION
A.
Previous Similar Events
LERs 91-08, 92-11, and 93-01 report automatic SBDG starts due to weather conditions.
[
i B. EIIS System and Component Codes Systems:
FK-Switchyard System f
EK-Emergency Onsite Power Supply System CE-Reactor Water Cleanup System EE-Instrument and Uninterruptible Power System l
KG-Nonessential Service Water System l
BI-Essential Service Water System l
Components:
EK-DG-Diesel Generator This report is being submitted pursuant to 10CFR50.73 (a) (2) (iv) h