ML20113J036
| ML20113J036 | |
| Person / Time | |
|---|---|
| Site: | Brunswick  |
| Issue date: | 01/18/1985 |
| From: | Zimmer S CAROLINA POWER & LIGHT CO. |
| To: | Vassallo D Office of Nuclear Reactor Regulation |
| References | |
| NLS-84-515, NUDOCS 8501250417 | |
| Download: ML20113J036 (6) | |
Text
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4 l
CD&L Carr., lina Power & Light Company SERIAL: NLS-84-515 J AN 181985 5
I I
Director of Nuclear Reactor Regulation Attention:
Mr. D. B. Vassallo, Chief Operating Reactors Branch No. 2 Division of Licensing United States Nuclear Regulatory Commission
{
Washington, DC 20555 f
BRUNSWICK STEAM ELECTRIC PLANT, UNIT NOS. 1 AND 2 L
DOCKET NOS. 50-325 & 50-324/ LICENSE NOS. DPR-71 & DPR-62 I
RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION:
[
- 1) ADEQUACY OF STATION ELECTRIC SYSTEM VOLTAGE a
- 2) TECHNICAL SPECIFICATIONS OF DEGRADED VOLTAGE RELAYS
Dear Mr. Vassallo:
In your letter dated November 14, 1984, Carolina Power & Light Company (CP&L) o was requested to provide information concerning the adequacy of the station electric system voltage and Technical Specifications of degraded voltage l
relays. Enclosed are CP&L's responses to the questions raised by your staff.
y Should you have any questions concerning this matter, please contact Mr. John Dietrich at (919) 836-6154.
Yours very truly, L
MtAW S
R.
immerman ager i
Nuclear Licensing Section i
JSD/ccc (964NLU)
Enclosures Mr. D. O. Myers (NRC-BNP) cc:
Mr. J. P. O'Reilly (NRC-RII)
Mr. M. Grotenhuis (NRC) r=-
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MSB8WJ88s@;
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/
411 Fayetteville Street
- P. O. Box 1551 o Raleigh. N C. 27602 Y
RESPONSES TO QUESTIONS Question 1A "To validate your new anal ais, provide (1) a description of the method f
-used in performing the test, (2) identification of the buses where the voltages were measured, and (3) an evaluation / conclusion of the analysis
'and actual test results (Ref. BTP PSB-1)."
Response
(1) The test was done by connecting current, voltage and power meters to the 4160-volt buses and 480-volt unit substations and then starting a circulating water pump and a screen wash pump.
Initial conditions required reactor power to be greater than 70 percent, all in-house loads were powered from the start-up transformer and three of four intake circulating water pumps were running.
(2) Voltage measurement equipment was connected in the following locations:
4160V 480V 2B Unit Sub 2E 2C Unit Sub 2F E4 Unit Sub E7
~
2D Unit Sub E8
.E3 MCC 2PB Com B After energizing the test equipment, the fourth circulating water pump was started and then the second screen wash pump was started.
Voltages during the motor starts were observed.
(3) The site' test demonstrated that the analytical values obtained from the Auxiliary System Design Optimization Program (ASDOP) studies were within acceptable limits of actual measured values. Results are shown in the following tables for measured test voltages versus voltage values predicted by ASDOP. The data is for two test situatious. The first is the startup auxiliary transformers (SAT) steady state before the additional motors were started. The second
-set was-taken during the circulating water pump start.
During Cire. Water SAT Steady State Pump Start
~ Bus Type Test Predicted Test Predicted Name Load Voltage Voltage Diff.
Voltage Voltage,
Diff.
2B BOP 4130 4212
+1.99 4130 4196
+1.6 2C BOP 4060 4104-
+1.08 3840 3886
+1.20 E4 Safety-4060 4104
+1.0 8.
3845 3886
+1.07 2D BOP-4060 4104
+1.08 3840 3886
+1.20 (964NLU/ccc)
Li
w:
Bus Type Test Predicted Test
' Predicted Name-Lord Voltage Voltage Diff.
Voltage Voltage Diff.
~
4060 4104
+1.08 3840 3886
+1.20 E3 safety ~
4060 4104
+1.08 3865 3836
+0.54 Com B BOP.
Sub 2E BOP 480 471
-1.83 456 442
-3.07 Sub 2F BOP 485 474
-2.27 462 445
-3.68 Sub E7 Safety 480 484
+0.83 456 457
+0.22 Sub E8. Safety 482 491
+1.87 460 464
+0.87 MCC 2PB. ' Safety 482 490
+1.66 458 463
+1.09
% Difference = Calc. Value - Measured Value Measured Value Question IB "Because of the fact the present Technical Specification allows interties
' through 4160 V buses between Units 1 and 2, the study should include an
.analyris of the plant operating scenario in which only one start-up transforuer (one off-site power source) supplies both units' plant loads per plant design.
This is to ensure that either of the start-up
-transformers has enough capacity to supply all connected loads and to avoid degraded system conditions for such an operation as had occurred at Arkansas Nuclear One (ANO)."
Response
-Unlike Arkansas Nuclear One, the start-up transformers at Brunswick 1 and 2 were -not designed such that one transformer can carry the auxiliary electrical load of both units. Upon loss of off-site power, instead of a load transfer to the other unit's start-up transformer, undervoltage
- --relays initiate shedding of-auxiliary system loads-and transfer of the emergency bus loads;to the emergency diesel generators.
'With the exception of 4160 V buses Common A and Common B, electrical interlocks prevent. crossties of 4160 V. buses ~between Brunswick,1 and 2.
.Our voltage drop analysis considered the. possibility of operating with the' tie. breaker'between the two buses closed (i.e., both Common A add Common B loads fed from either unit's distribution system.)' It was found that adequate 1 voltage regulation could be maintained for both accident and nonaccident conditions.
Question 2-c "In reference to the CP&L Technical Specification revision request dated
-July 29, 1982 regarding a change in 4160 V emergency bus undervoltage
.setpoints and surveillance requirements, we have reviewed.the request and
. find:that no supporting' documents have been provided as to how the proposed trip valueo and channel check intervals were selected."
T (964NLU/ccc)
V
.+
o-7
Response
The present Technical Specifications (TS) refer to the undervoltage Device 27 on BOP buses IC, ID, 2C, and 2D.
An investigation deternined that these Technical Specifications were generated based on a plant modification to install the 2 7/59E relays on Emergency Buses El, E2, E3, and E4, but inappropriately referenced the undervoltage Device 27 in the BOP buses. Thus, trip values in the Technical Specifications were generated for the BOP bevice 27.
The correct device is Generel Electric Relay Type IAV53K, device number 2 7/59E. The trip setpoint should be 98 t 4.9 volts on a 120 volt basis (3 430 t 172 volts on a 4.16 kv basis) with a trip time of 1.5 75 seconds at 0 volts. Allowable values are determined by the inverse time characteristics for voltage less than the trip setpoint. The relay will not trip for voltages greater than the trip setpoint.
The 98 volt trip setpoint was established in the undervoltage studies and relay coordination settings and curves for the 4.16 kv switchgear. These studies were developed as part of the original plant design. The tolerance of t4.9 volts is based on 5% of the 98 volt trip setpoint.
This tolerance was established by General Electric Company, the manufacturer of this relay device. The trip setpoint for 4.16 kv basis is in proportion to the 120 volt trip setpoint (118.9 nominal operating voltage).
The trip time of 1.5 75 seconds at 0 volts is based on the time-voltage curves for this type of relay as shown in Attachment 1.
The trip time is determined from the left vertical axis (time in seconds) where intersected by the appropriate time curve. The appropriate time curve corresponds to the ratio of the trip setpoints of the relay device. As discussed, the studies were developed as part of the original plant design and establish the undervoltage trip setpoint at 98 volts (right hand contact). These studies also establish the overvoltage trip setpoint at 105 volts (left hand contact). The ratio of the trip setpoints is approximately 93%. The 93% time-voltage curve corresponds to a 1.5 second trip time.
It should be noted that the 100% voltage in the horizontal axis corresponds to the overvoltage trip setpoint of 105 volts (left hand contact closes).
As a result, the relay should trip in approximately 1.5 seconds when the voltage drops from the nominal operating voltage of 118.9 volts on a 120 volt basis (4160 volts en a 4160 volt basis) to 0 volts, according to the 93% time-voltage curve shown in Attachment 1.
Based on the manufacturer's tolerances of 5%, the trip time of 1.5 75 seconds at 0 volts is proposed in the TS revision request.
No specific allowable value is shown in the TS revision request as there is an infinite number of voltage / time combinations that will not result in a relay trip.
The proposed surveillance requirements for the 2 7/DV relays consist of monthly functional testing and channel calibration every 18 months. The once per shift channel check presently performed on these relays consists of a check for the presence of " targets" indicating the relay is or had tripped, and verification that the installed voltmeters on the 4.16 kV bus indicate greater than 3800 volts. The bus voltage information is available in the control room and is, therefore, redundant. The targets (9 64NLU/crs)
mo.
provide an indication that the relay is in, or was temporarily in, the tripped' position and.does not provide a useful indication of relay operability.
In' addition, the relays are arranged in.a two out of three-logic for reliable actuation of their safety function without spurious actuation.. For these. reasons; the once per shif t channel check does not
. provide' a significant indication of the operability of the relays and was removed from the proposed technical specification.
A i
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'EH-l'814 "Vcitags Relays Typ21AV ATTACHMENT I
PERCENTAGE OF YOLTAGE TO CLOSE LEFT CONTACTS l
AT nMICM RIGHT CONTACTS *ERE SET TO CLOSE.
~
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95 %
90 505 60s 705 80s 955
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f K's TlWE TO CLOSE RIGHT CONTACTS eMEN VOLTAGE IS
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t SUDDENLY REDUCED FROW VALUE EQUAL TO OR GREATER 4
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f-O TMAN VOLTAGE REculRED TO CLOSE LEFT CONTACT, j
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T0 VALUES ON THE CURVE.
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Fi g. 2 Time-Voltage curves For. Type I AV53A And l AV538 Relays 6
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