ML19344B265
| ML19344B265 | |
| Person / Time | |
|---|---|
| Site: | Big Rock Point File:Consumers Energy icon.png |
| Issue date: | 08/21/1980 |
| From: | Hoffman D CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | James Keppler NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| Shared Package | |
| ML19344B263 | List: |
| References | |
| TASK-08-01.A, TASK-8-1.A, TASK-RR NUDOCS 8008260056 | |
| Download: ML19344B265 (9) | |
Text
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General Officee: 212 West Michigen Avenue. Jackson Michigan 49201
- Area Code 517 788-05S0 August 21, 1980 Mr James G Keppler Office of Inspection and Enforcement Region III US Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 DOCKET 50-155 - LICENSE DPR BIG ROCK POINT PLANT - RESPONSE TO GENERIC ISSUE - DEGRADED GRID VOLTAGE By letter dated July 9, 1979, the Commission requested additional information on the generic issue cf on-site power systems.
The attached Consumers Power Company response to the enclosure questions is entitled " Response To Request for Additional Information Big Rock Point Degraded Grid Voltage." The computer analysis which provided the requested data was verified by a tesu completed on June 26, 1980.
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David P Hoffman (Signed)
David P Hoffman Nuclear Licensing Administrator CC Director, Office of Nuclear Reactor Regr.lation Director, Office of Inspection and Enforcement NRC Tesident Inspector-Big Rock Point l
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RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION BIG ROCK PLANT DEGRADED GRID VOLTAGE Item 1 Provide data showing the maximum and minimum voltages reflected at the 480 V safety-related bus when the auxiliary systems are being supplied by the:
a.
Station generator.
b.
138 kV off-site system.
c.
Backup 46 kV system.
Response to Item 1 a.
Station Generator - Maximum Voltages 2400 V Bus LC #1 LC #2 Bus 1A*
Bus 2A*
(2.4 kV)
(480 V)
(480 V)
(480 V)
(480 V) 1.0477 1.0026 1.0061 1.0013 1.0053 Station Generator - Minimum Voltages 2400 V Bus LC #1 LC #2 Bus 2B*
Bus 2C*
(2.4 kV) -
(480 V)
(480 V)
(480 V)
(480 V)
.9317
.8819
.8760
.8803
.8710 b.
138 kV Off-Site System - Maximum Voltage 2400 V Bus LC #1 LC #2 Bus IF*
Bus 2A*
(2.4 kV)
(460 V)
(480 V)
(480 V) 480 V
.9941
.9526
.9695
.9516
.9691 138 kV Off-Site System - Minimum Voltage 2400 V Bus LC #1 LC #2 Bus IA*
Bus 2A*
(2.4 kV)
(480 V)
(480 V)
-(480 V)
(480 V)
.9088
.8627
.8817
.8608
.8812 c.
Backup 46 kV System - Maximum Voltage 2400 V Bus LC #1 LC #2 Bus 1A*
Bus 2A*
(2.4 kV)
(480 V)
(480 V)
(480 V)
(480 V)
.9773
.9248
.9303
.9233
.9287 rp0880-0318b-89
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Backup 46 kV System - Minimum Voltage 2400 V Bus LC #1 LC #2 Bus 2B*
Bus 2C*
(2.4 kV)
(480 V)
(480 V)
(480 V)
(480 V)
.9317
.8760
.8819
.8803
.8710
- According to Attachment 1, there are 13 - 480 V buses.
Instead of listing every value, only the highest values were listed when looking at maximum voltage and the lowest values were listed when looking at minimum voltage.
Item 2 Provide a voltage analysis to justify your choice of placing.the proposed second level undervoltage protection on the 2400 V bus as opposed to the 480 V safety-related bus.
Response to Item 2 The above response to Item 1 provides the voltage drop calculations which shows that the voltage ratio between the 2400 V bus and the 480 V safety-related bus does not vary significantly under any voltage conditions.
Therefore, it is technically acceptable to monitor the 480 V bus voltage from the 2400 V bus as long as the proper transformer and cable impedances are used to determine the voltage drop.
Consumers Power Company desires to protect all of the station equipment from sustained undervoltage conditions, not just the safety-related bus; therefore, the second level of undervoltage protection was placed on the 2400 V bus and the protective action is taken on the 2400 V incoming breaker.
Item 3 Provide the voltage set point of the existing undervoltage relays on the 480 V safety bus and their time delay.
Response to Item 3 A complete description of the existing 2400 V and 480 V undervoltage relays, their functional responsibilities, their voltage set points, and their time delays is contained in Attachment 2 entitled, " Big Rock Plant - 2400 V Bus Transfer and Undervoltage Scheme."
Item 4 Provide the total elapsed time from operation of second level undervoltage
' protection system to the initiation of the existing undervoltage relays to start the diesel generator.
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3 Response to Item 4 Attach'nent 2, " Logic Diagram - Safety Bus 2B Undervoltage Protection," in the 4
June 14, 1978 letter to the staff shows that a 10.0-second time delay exists between the operation of the second level of undervoltage protection and Tripping Breaker 1136. Tripping Breaker 1136 results in an immediate loss of voltage on the safety bus which causes the operation of the 27-1 and 27-2 relays. These relays are instantaneous so the total time lapse between the operation of the second level relays and the starting of the diesel generators is 10.0 seconds. A revised copy of this logic diagram (Attachment 3) is included and the revisions are explained below.
1.
The previous relay designation, 27-3, has been changed to 127-10.
2.
The voltage set points for the second level of undervoltage protection relays were removed from the diagram. The exact setting points are normally filed with the relay settirg sheets which are controlled by specific procedures and are not usually shown on logic diagrams.
3.
The logic sequence was changed from 2/.i ;o 3/3. 3/3 protection logic is normally used on all system UV relay schemes. The NRC staff has shown that they believe that the off-site power source is the preferred source due to reliability and availability. The 3/3 logic provides the greatest assurance that the off-site source will not be lost. This precedent was set by using 3/3 in the Palisades version of the Undervoltage Modification which was completed this year.
Item 5 Provide the results of your voltage analysis for the full load and no-load conditions for each bus of the on-site distribution system.
Response to Item 5 a.
Full Load 2400 V Bus LC #1 LC #2 Bus 2B*
Bus 2C*
(2.4 kV)
(480 V)
(480 V)
(480 V)
(480 V)
.9937
.9422
.9476
.9461
.9375 b.
No Load 240 V Bus LC #1 LC #2 Bus lA*
Bus 2A*
(2.4 kV)
(480 V)
(480 V)
(480 V)
(480 V) 1.0000
.9589
.9756
.9572
.9752
- Instead of listing all thirteen 480 V buses, only the two with the lowest voltages are listed. The remainder of the values are on record if they are needed.
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1 BIG ROCK PLANT 2400 V BUS TRANSFER AND UNDERVOLTAGE SCHEME I.
GENERAL DESCRIPTION The auxiliary power system consists of the main station power system, the standby station power system and the emergency power system.
The auxiliary power system is normally supplied from the main generator and/or 138 kV system which is called the main station power system. The auxiliary power system can be supplied from the 46 kV system which is called the standby station power system. Transfer to standby station power is initiated by low voltage.
The emergency power system supplies the safety-related bus from the 480 V diesel generator. This system provides power for those services neces-sary to prevent serious damage or hazards to equipment and personnel in the event of loss of the main and standby station power.
II.
UNDERVOLTAGE BUS TRANSFER & BUS LOAD SHED SCHEME If the 2400 V bus voltage decays beloc 50% of the nominal 120 V trans-former secondary for 3 seconds, an automatic transfer from the main station power to the standby station power will occur. The 480 V safety-related bus undervoltage relays also operate since the auxiliary power systems voltage decayed below 50% of the nominal 120 V transformer secondary. The safety-related bus undervoltage relays initiate starting of the diesel generator. After the bus is ds-energized more than 2 seconds but less than 4.5 seconds, the following loads will be shed:
The 2400 V reactor feed and reactor recirculating pumps 1 and 2, the 480 V condensate pumps 1 and 2, the radwaste motor control center bus 1E and the reactor building ventilation system motor control center bus 2D.
With a successful transfer the 480 V condensate pumps 1 and 2 will automatically start 6 seconds after the associated 480 V buses are energized. The 2400 V motors, motor control center bus 1E and motor control center bus 2D must be sequenced on manually.
If the transfer is unsuccessful, 4.5 seconds after the bus is de-energized the 480 V condenser circulating water pumps 1 and 2 will be tripped. When the diesel generator output voltage reaches 91.7% of the nominal 120 V transformer secondary, bus tie breaker lA-2B or 2A-2B will be tripped. One bus tie breaker is normally open and one normally closed so tripping would occur at the closed breaker. With both bus tie breakers open, the safety-related bus de-energized and the diesel generator output voltage at 91.7%, the diesel generator breaker will close automatically, energizing the safety-related bus. This will rp0880-0318c-89 e
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maintain the plant in a safe shutdown condition. Extra plant services must be selected manually.
Once the diesel generator is running and connected to the safety-related bus no loads are shed except via individual circuit breaker operation or the protective relays on the diesel generator. The diesel generator overload relays will alarm only.
Attached is Table No 1 which gives the sensor locations, settings and function.
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MFR.
RELAY ACCEPTABLE ACTUAL CAT.
SAFETY SFTSOM I4 CATION UtNBER TYPE SPPTING RANCE SF.TPING DATA RFt.ATED ACTl!ATFS 2400V Dus 27 NBV 18V-22V 20 Unbalance Yes Allows transfer for balanced 3-phase voltage decay 127-1 HGA17A Fixed Setting 15 cycle DO Hot 40% PU No Trips Reactor Circulating M p No 1 20-30% DO 127-2 HGA17A Fixed Setting 15 Cycle DO Hot 40% PU No Trips Reactor Circulating Pump No 2 20-30% Do 127-3 AGASTAT 2 see TDC 50% Do No Trips Reactor Feed Pu=p No 1 g
127-4 AGASTAT 2 sec TDC 50% DO No Trips Reactor Feed Pump No 2 127-5 AGASTAT 1.9-2.1 see TDC 2 cee TDC 50% DO No Trips Condensate Pump !"o 1 (h80V Motor)
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5.7-6.3 see TD0 6 see TD0 Automatic Reenergize Condensate Pump No 1 (L60V Motor) 127-6 AGASTAT 1.8-2.2 see TDC 2 see TDC
$0% DO No Trips Condensate Pump No 2 (LSOV Motor) 5.h-6.6 see TD0 6 see TD0 Automatic Reenergize Condensate Pump Nce 2 (h80V Motor) 127-7 AGASTAT h.05-4.95 see TDC 4.5 see TDC 50% DO No Trips Condenser Circulatir.g Water Pu=p No 1 (18CV Motcr) 1.8-2.2 see TDO 2 see TD0 Auto Reenergize Cond Circ' ins Water Pump No 1 (LBOV ".stor) 127-8 AGASTAT k.05-4.95 see TDC h.5 sec TDC 50% DO No Trips Condenser Circulating Water Pucp No 2 (LSOY Motor) 1.8-2.2 see TD0 2 see TD0 Auto Reenergize Cond Cire'ing Wster Pump No 2 (L80V Motor) i 12T-9 AGASTAT 2.85-3.15 see TDC 3 see TDC 50% Do Yes Init. Trip or 1126 Breaker and Clcse or 7726 Breaker h80V Bus lA 27-3 AcASTAT 2 see TDC 50% DO No Trips Radvaste Motor Control Center Bus lE j
L80V Bus 2A 27 4 AGASTAT 2 see TDC 50% DO No Trips Reactor Bldg Vent Sys. Motor Control Center Bus 23 480V Bus 2B 27-1 HGAllJ Fixed Setting Cold 60% PU Yes Init Diesel Generator Start and Supervises Cen Breater Hot 80% PU Close 40-50% Do 27-2 HGA11J Fixed Setting Cold 60% PU Yes Init Diesel Generator Start tnd Supervises Gen Brealer Hot 80% PU close 40-50% DO D-G h80V 59 PJVllA 106V-ll6V 110V Yes Supervises Cen Breaker Close Trips Tie Breakers lA-2B
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