ML19329D606
| ML19329D606 | |
| Person / Time | |
|---|---|
| Site: | Crystal River  |
| Issue date: | 02/06/1977 |
| From: | Rodgers J FLORIDA POWER CORP. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8003160231 | |
| Download: ML19329D606 (8) | |
Text
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'ower January 6, 1977
.,nau-Mr. John Stolz Branch Chicf
- "I'93 Light Water Reactors Branch I
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Division of Project Management
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U.S.
Nucicar Regulatory Commission e
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Washington, D.C.
20555 19 / 7 1
Subject:
Florida Power Corporation Crystal River Unit #3 p
g Docket No. 50-302 W
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Dear Mr. Stol:
On October 4, 1976, we received your October 1, 1976 Request for Additional Information concerning equipment failures dur-ing a degraded grid voltage condition.
Specifically, you requested Florida Power Corporation to evaluate the design of the CR#3 Class IE electrical distri-bution system to determine if the operability of safety related equipment, including associated control circuitry or instrumen-tation, can be adversely affected by short term or long term degradation in the grid system voltage.
Attached are forty (40) copies of our response to the questions contained in Enclosure No. 2 of your October 1, 1976 letter.
Our response is in question and answer format to facilitate your review.
If further discussion of this matter is required, please do not hesitate to contact this office.
Very truly yours, J.
T.
Rodge rs Asst. Viec l'res ident JTR/iw Attachments.
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Ifl WIT?iESS WHEREOF, the applicant has caused its name to be hereunto signed i
by J.T. Rodgers, Assistant Vice President, and its corporate seal to be
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t hereunto affixed by Betty f4. Clayton, Assistant Secretary, thereunto duly 1 -
authorized the 6th day of January,1977.
FLORIDA POWER CORPORATION By J.T.GRodgers O
Assistant Vice President
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Betty t.47Clayton Assist' ant Secreta (CORPORATE SEAL)
Sworn to and subscribed before me this 6th day of January, 1977.
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- c. n tiotary Public fly Commission Expires:
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tiotary Public State of Florida at Large f4y Comission Excires July 9.1978
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QllESTION 1.a:
Describe the plant conditions undc r which the plant auxiliary systems (safety related and non-sa fety re-lated) will be supplied by of fsite power.
Include an estimate of the fraction of normal plant operating time in which this is the case.
RESPONSE
The unit is provided with one full si:e Auxiliary Transformer and one full size Start-up Transformer.
The Auxiliary Transformer is connected to the Generator and will serve as the normal source of power to the non-safety related buses.
The start-up transformer is connected to the 230 KV substation and serves as the normni source for the safety related buses as well as providing a source of power for start-up, shut down and after shutdown requirements.
Each of the trans-formers has two isolated secondary windings, one at 6900 volts and one at 4160 volts.
Each transformer is capable of supplying the normal full load require-ments of the unit.
Transfer capability is provided so that upon loss of the unit voltage, the non-safety related buses will automatically be trans ferred to the Start-up Transformer.
Based on the above, the percentage of time the buses are supplied from offsite power during normal operation is as follows:
Safety Related Buses 100%
Non-Safety Related Buses 0%
QU ESTION 1.b:
The voltage used to describe the grid distribution system is usually a " nominal" value.
De fine the normal operating range of your grid system voltage and the corresponding voltage values at the safety related buses.
RESPONSE
Norma l operat ing range o f 230 KV grid system is 233 KV to 242 KV.
Nominal value is 240 KV.
The corresponding voltage values at the sa fety related buses a re as follows:
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Git t li al60V 480V VO!,TAGli illlS BUS 238 KV 4200 V 485 V 240 KV 4235 V 489 V 242 KV 4270 V 493 V QUESTION 1.c:
The transformers utili::ed in power systems for pro-viding the required voltage at the various system distribution 1cvels are normally provided with taps to allow voltage adjustment.
Provide the results of an analysis of your design to determine if the voltage profiles at the safety related buses are satisfactory for the full load and no load conditions on the system and the range of grid voltage.
RESPONSE
The voltage values at the safety related buses for no load and full load conditions and the range of grid voltage are as follows:
No Load Full Load GRID 4160 V 480 V 4160 V 480 V VOLTAGE BUS BUS BUS BUS 238 KV 4200 V 485 V 3961 Y 451 V 240 KV 4235 V 4S9 V 3994 V 454 V 242 KV 4270 V 493 V 4027 V 458 V These voltage values are satisfactory for the full load and no load conditions on the system and the range of grid voltage.
QUESTION 1.d:
Assuming the facility auxiliary loads are being carried by the station generator, provide the voltage profiles at the safety buses for grid voltage at the normal maximum value, the normal minimum value, and at the degraded conditions (high o r low vol tage,
current, etc.) which would require genera tor t rip.
IttiSl'ONSli:
The normal operating range of the Unit 3 Generator is 22 KV t 5'.,
or 20.9 KV to 23.1 KV.
The voltage values
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A at the safety related buses for no load and full load conditions and at the normal operating limits of the generator are as follows:
No Load Full I.o a d GEN.
4160 V 480 V 4160 V 480 V VOLTAGE BUS BUS BUS BUS 20.9 KV 4053 V 468 V 3867 Y 439 V 22 KV 4267 V 492 V 4071 V 462 V 23.1 KV 4480 V 517 V 4274 V 485 V The Unit 3 Generator is designed to trip only during an underfrequency trip condition at 58.0 H;.
The underfrequency device is set to trip the unit in 12 seconds at 58.0 HZ.
The voltage output is never expected to vary outside the normal operating range of the generator.
During an underfrequency condition, the generated voltage may be reduced.
To maintain rated KVA at the less-than-rated frequency, a com-parable increase in excitation to the generator field windings is required.
This is accomplished automa-tically with the voltate regulation system of the generator.
QUESTION 1.e:
Identify the sensor location and provide the trip setpoint for your facility's Loss of Offsite Power (undervoltage trip) instrumentation Include the basis for ~your trip setpoint selection.
RESPONSE
Each 4160 V and 480 V safety related bus has undervoltage relays.
These relays are located in the respective switchgear panels.
The 4160 V setpoint is 2375.1 V, or 56.5%.
The 480 V setpoint is 271.4 V or 56.5%.
The i
480 V starters and contactors are capabic of withstand ;
ing a momentary voltage drop of 55% of rated voltage for a period of 2 seconds without dropping out.
This is the basis for an undervoltage trip setpoint of 56.5%.
Qlll!ST ION 1.f:
Assuming operation on of fsite power and degr :dat ion of the grid system voltage, provide the voltage vaines at the. safety related buses. corresponding to the maximum value of grid. voltage and the degraded grid voltage corresponding to the undervoltage trip setpoint.
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.laximum value of grid voltage is 242 KY.
At this value
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the voltages at the 4160 V and 480 V buses are re-spectively 4270 V and 493 V.
The grid voltage corresponding to undervoltage trip on 4160 V bus at 2375.1 V is 142,736 V.
QUESTION 1.g:
Utilizing the safety related bus voltage values identified in (f), evaluate the capability of all safety related loads, including related control circuitry and instru-mentation, to perform their safety functions.
Include i
a definition of the voltage range over which the safety related components, and non-safety components, can operate continuously in the performance of their design function.
RESPONSE
All magnetic devices (contactors and starters) associated with the 480 V safety related buses are designed to operate at 55', of rated voltage for 2 seconds.
All safety related and non-safety related components are 4
i designed to operate continuously at i 10% of their rated voltage.
l QUESTION 1.h:
Describe the bus voltage monitoring and abnormal voltage alarms availabic in the control room.
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RESPONSE
Voltmeters are provided in the control room for each of the unit auxiliary buses (safety and non-safety related).
Also potential transformer trouble alarms (indicating, for safety related buses, that one out of three undervoltage relays has operated or, for i
non-sa fety related buses, that one out of two under-i voltage relays has operated) and undervoltage alarms on each of the buses are available in the control room.
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QUESTION 2:
The functional sa fety requirement of the undervoltage trip is to detect the loss of offsite (pre fe rred )
power system voltage and initiate the necessary actions required to transfer safety related buses to the onsite power system.
Describe the load shedding feature of your design (required prior to transferring to the onsite [ diesel generator] systems) and the capability of the onsite systems to perform their function if the load shedding feature is maintained after the diesel generators are connected to their respective safety buses.
Dese. ribe the bases (if any) for retention or reinstatement of the load shedding function after the diesel generators are connected to their respective buses.
RESPONSE
Loss of the preferred AC power source will result in undervoltage relay action on the 4160 volt En gin ee red Safeguards Buses 3A and 3B.
Each bus is equippedwith undervoltage relays to provide this action.
The operation of these relays will result in tripping all loads connected to the buses except for the Engineered Safeguards Block 1 loads.
The operation of these relays will also isolate the two safety related channels entirely from each other.
The load shedding feature is not maintained after the Diesel Generators-are connected to their respective buses, the re fo re, this part of the question is not applicabic to Crystal River Unit 3.
QUESTION 3:
l Define the facility operating limits (real and reactive power, voltage, frequency and other) established by the grid stability analyses cited in the FSAR.
Describe the operating procedures or other provisions presently 4
in effect for assuring that your facility is being operated within these limits.
RESPONSE
Genera t or Speci fications 989,400 KVA 22 KV 25,965'A 0.9 P.F.
3 Phase 6 0 '112 1300 RP.\\1
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.Oye ra t ing Limi ts Ala.s i mum Real Power - 890.46 blN.
Fla.dmun Reac t ive Powe r - 4 31. 2 7.'.IVAR Voltage Limits - 22 KV t 5%
Frequency Limit 58 HZ The facility will be operated within the above limits as per Crystal River Unit 3 Opera ting Procedure OP-204 for-Power Operation.
QL'"9 TION 4:
Provide a description of any proposed actions or modifications to your facility based on the results of the analyses performed in response to items 3 above.
RESPONSE
There are no actions or modifications necessary on Crystal River Unit 3 based on the above results 1-3.
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