ML17341B176

Forwards Voltage Analysis of 120-volt Ac Sys in Response to Question 5 of 811022 Request,Per 820224 Commitment.Response to 820319 Ltr Re Adequacy of Electrical Distribution Sys Encl

ML17341B176
Person / Time
Site:	Turkey Point
Issue date:	05/20/1982
From:	Robert E. Uhrig FLORIDA POWER & LIGHT CO.
To:	Varga S Office of Nuclear Reactor Regulation
References
L-82-211, NUDOCS 8205250002
Download: ML17341B176 (23)

Text

REGULATORY ORMA'TION DI'STRIBUTION 'SY M ('R IDS)

AQCE'SSION NBR:8205250002 DOC ~ DATE: 82/05/20 NOTARIZED: NO DOCKET FACIL:.50-250 Turkey Point Plantr Un)'t 3r Florida Power and Light 'C 05000250 50 251 Turkey Point Plantr 'Unit 4r Flor ida 'Power and Light C 05000251 AUTH'PME AUTHOR AFFILIATION UHRIGpR ~ E ~ Fl or ida:Power L Light Co ~

'RHC IP NAME RECIPIENT AFFILIATION VARGAg S ~ A ~ Operating Reactors Branch 1

SUBJECT:

Forwards volitage analysis of 120 volt ac sys in response to Question '5 of 811022 reauestiper 820224 commi,trent,Response to 820319 ltr re adequacy of electrical distribution sys enc 1*.

DISTRIBUTION CODE- A001S TITLE: General

. COPIES 'RECEIVED:LTR g ENCL Distribution for after Issuance of Operating License J SIZEt.

NOTES:

RECIPIENT ~COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID 'CODE/MANE LTiTR ENCL ORB 01 BC 01 7 7 INTiERNAL: ELD/HDS4 i0 NRR/DHFS DE'PY08 1 1 NRR/DL DIR 1 RAB 1 0 NRR/DSI/RAB 1 1 REG F ILE 04 1 1 RGN2 1 1 EXTERVAL: ACRS 09" 10 10 LPDR 03 1 1 NRC,'PDR 02 1 1 NSIC 05 1 1 NTIS 1 1 TOTAL NUMBER OF COPIES REQUIRED: L'TTR 28 ENCL 26 1

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FLORIOA POWER & LIGHT COMPANY May 20, 1982 L-82-211 Office of Nuclear Reactor Regulation Attention: Mr. S.A. Varga, Chief Operating Reactors Branch gl Division of Licensing U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Dear Mr. Varga:

Re: Turkey Point Units 3 5 4 Docket Nos. 50-250 and 50-251 Ade uac of Station Electrical Distribution S stem Volta es In our letter (L-82-65) dated February 24, 1982, we stated that we would provide a voltage analysis of the 120 volt AC system in order to respond to question 5 of your October 22, 1981 request. That analysis is 'attached as Enclosure 1.

Enclosure 2, to this leter, is our response to your letter dated March 19, 1982 concerning the adequacy of station electrical distribution system voltages.

Very truly yours, ert E. Uhrig Vice President Advanced Systems 8 Technology REU/JEM/mbd cc: J.P. O'Reilly, Region II Harold F. Rei s, Esquire pO~

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ENCL'OSURE 1 Page 1 Re: Turkey. Point Units 5 4 Docket:flos. 50-250, 50-251 Adequacy of 'Station Electrical Distribution S stem Volta es In response to NRC letter dated October 22, 1981 RE: Request for additional information (Round 3) Turkey Point -Units 3 & 4 (TAC Nos. 12964 & 12965) Adequacy of Station Electric Distribution System Voltages.

Ref. 1: FPL letter (R. Uhrig) to NRC '(S. Varga), dated February 24,, 1982 (L-82-65)

Ref. 2: Florida Power & Light letter (R. Uhrig) to NRC (ST Varga), dated December 18, 1980.. (L-80-411)

As stated in our letter L-82-65 dated February 24, 1982 (Ref. 1), in answer to the subject NRC letter to R. Uhrig dated October 22,,1981, a portion of the r'esponse to question 5 was deferred to allow for an extended voltage analysis.

Contained herein is the requested voltage analysis of the plant's 120VAC system.

Our letter L-82-65 (Ref. 1). provided the manufacturer's guaranteed pick-up voltage for the motor starters. Tests were conducted'ne the motor starters and control power transformers to determine the actual pick-up voltages.

Considering the cable and control transformer voltage drops, calculation were then performed to obtain the minimum bus voltages required. These voltages are provided in Attachment A. Note that no size 3 starters are used in safety related applications'he minimum .required bus voltages are al'1 less than the transient vol'tages experienced on start of all safety motors provided in attachment C of our letter L-80-411 dated December'18, 1980 (Ref. 2).

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'I Attachment A Page 1 of 1 Volt~ac An~al sis Results Minimum Bus Voltages Required to Pick-U Starters UNIT 3 BUS VOLTAGES 480VHCC A 33 2* 386 480V HCC B 381 381

'480V MCC C 394 332 "t 480 iMCC D 392

+ Not on 'Unit '4 These HCC's utilize only size 1 starters, all other HCC's,utilize size 1, 2 and 4 starters.

0 I El'ICL'OSURE 2 Page 1 Re: Turkey Point Units 3 & 4 Docket. Nos. 50-250, 50-251 Adequacy of Station Electrical Distribution S stem Volta es In response to NRC letter to Florida Power & Light dated'arch 19, 1982.

RE: Request for Additional Information (Round 4) Turkey Point Units 3 & 4 Adequacy of Station Electric Distribution System Voltages.

Ref. 1: Florida Power & Light letter (R. Uhrig) to NRC (S. Varga), dated December 18, 1980.

2: NRC letter to Florida Power & Light dated August 8, 1979.

Question 1: The analysis results and documentation submitted in Reference 1 and 2 demonstrate that the Class IE motors will successfully start within the minimum starting voltage and that the +10%

design voltage rating is not exceeded. However, the results do not verify that the steady state voltage at the terminals of the Class IE equipment is within the -10% design voltage rating.

Therefore, submit the "worst case" steady state load terminal voltage at all Class IE voltage distribution levels.

Answer: Attachment A provides the worst case steady state voltages with all safety loads running and after start of the largest non-Class IE motor, assuming the minimum grid voltage of 235KV. The steady state voltages were analyzed for worst cases 2 and 9 presented in our letter L-80-411 datedDecember 18, 1980 (Ref. 1). Since no voltage is less than minus 10% of 4000 volts (3600 volts) or less than minus 10%

of 460 volts (414 volts), proper voltages levels are assured.

Question 2: What is the duration of the starting transient when starting the steam generator feedwater pump (Cases 2 and 13 of Ref. 1)?

Discussion This duration time with respect to tne transient voltage is needed to verify that there will be no spurious actuation of,the undervoltage relays during the load starting.

Answer: The starting transi'ent is approximately 7 seconds in duration.

Question 3: 'Submit details of the test verification performed (i.e, plant operating mode, bus loading percentages, distribution level voltages, etc.) and verify that, the "less than 3%" correlation difference (Ref. 1') is applicable to both steady state and transient conditions.

Answer: The plant was operating with both units at full power during the test.

Bus voltages and loadings at the time of the test are provided in Attachment B. A mathematical model was developed from transformer nameplate data and cable impedance calculations. A voltage analysis using the measured loads was then performed to calculate the bus voltages based on the model. The results of this analysis. and the percent error are provided in Attachment C. 'The measured values correlated closely with the results of the analysis using the mathematical model, therefore the model is considered accurate. Since

Page 2 the impedence (resistance and reactance) of the system is constant the model can be used to analyze voltage drops due to steady state running loads as well as instantaneous voltage drops due to starting transients.

Question 4: The scope of the voltage analyses to be submitted as outlined in Ref. 4 applies to all available offsite source connections to the onsite distribution system. For the available source connections as defined in Ref. 3, an analysis was submitted only for the startup transformer connection. Since backfeeding units'edicated through the main transformer and unit auxiliary transformer and the use of the adjacent unit's startup transformer are viable source connections for each unit, a worst case voltage analysis (under-voltage and overvoltage) is required.

Discussion - If documentation can be provided to verify that due to transformer impedances, bus loading conditions and configurations, etc.,

(following the guidelines in Ref. 4) that the voltage drops experienced (both steady state and transient) do not exceed those'lready submitted, then the analysis results of these viable source connections need not be submitted. However, documentation should be provided to verify that these source connections were, analyzed and that each have the capacity and capability to supply adequate voltage to the Class IE equipment within the design voltage ratings under worst case conditions.

Answer: In accordance with Reference 1, Guideline 3, the voltage analyses were performed assuming all automatic actions occur .as designed. The plant's distribution systems are normally powered via the unit auxiliary transformers when the unit is at power. A safety injection signal initiates an automatic fast transfer to the unit's start-up transformer, which then powers. all safety related equipment. If the unit were being powered via the main and auxiliary transformer (by removal of the isolated phase bus links to the main generator) and a safety injection signal were to occur, the fast transfer to the, start-up transformer would occur, as above. If the unit were being, started up or shut down, it would already be connected to it's start-up transformer. In any event, if the start-up transformer were not availble, or its breakers failed to close, the emergency diesel generators would automatically start and sequence safety related loads onto the buses.

The only other possible connection to offsite power is via the adjacent unit's, start-up transformer. Only the "A" buses of each unit can be connected in this manner. Such connectionrequires careful, deliberate, manual action, which would include reduction of load on the buses, and would only be done with the unit shutdown. If a safety injection occured when so connected, the "A" bus safety related equipment would be automatically started from power supplied by the adjacent unit's start-up transformer. However, the small additional impedence from the longer cable run (the transformers are essentially identical) is more than offset by the much.-. reduced loading due to the unit being shutdown. In accordance with the Guidelines of Reference 1, the worst case was analyzed and submitted in our letter of December 18, 1980 (L-80-411, Ref. 1).

4i Attacnment A Pa 1 of 2 VOLTAGE ANALYSIS RESULTS UNIT I/3 Horst Case Stead State Assumin All Rafet Loads R~nnnin and After Start of Lar est iCon-Class IE'otor Bus Volta es Grid at 235KV Case 2 Case 9 4KV Bus'A* 3991 4051 4KV .Bus. A*'946 4013 4KV Bus B>> 4024 3964 4KV Bus B>>>> 3928

'480V:. LCA 449 4'56 480V'. LCB 453 446 d80lf jCc 449 456 480V. g~ 45 441 480V MCC 4 447 454 480V MCC B 447 439 480V MCC, C 445 452 480V MCC D '436 427

• High side of current limiting reactor

• • Low side of current limiting reactor

I Attachment A Page 2 of 2 VOLTAGE ANALYSIS RESULTS UNIT 84 Worst Case Stead State Assumin All Safet Loads Runnin and After Start of L~ar est Non-Class IE Motor Bus Volta es Grid at 235KV Case 2 Case 9 4KV Bus A>> 3987 4050 4KV Bus A>>>> 3942 4012 4KV Bus B>>

4032'007 3970'936 4KV Bus B*>>

480V LCA 447 455 480V LCB 454 446 480V LCC 450 457 480V LCD '461 451 480V MCC A 444 452 480V MCC B 451 4'43 480V MCC C 447 455 480V MCC D

• High side of current limiting reactor

• >> Low side of current limiting reactor

+ Not on Unit //4'

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Attachment B Pape 1 of 2 Measured Bus Volta es and Loads. Unit i/3 Bus Volta e Bus KVA 4KV Bus A>> 4204 9655 4KV Bus A*>> 8484 4KV Bus B>> 4207 14122 4KV Bus B** 4448

'480V LCA 467 447 480V LCB '476 270 480V LCC 474 332

'480V LCD 470 455 480V MCC A 415 480V MCC B 472 209 400V MCC C 472 131 480V MCC D 460 462

>> High side of current limiting reactor

• • Low- side of current limiting reactor

+l- Bus voltage values not available

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'I Attachment B Page 2 of 2 Measured Bus Volta es and Loads Unit f/4'us Volta e Bus KVA KV Bus A>> 4239 9655 KV Bus A>>* 6459 KV Bus B>> 4179 14122 KV Bus B>>>> 6133 SOV LCA '474 346 80V LCB 478 148 SOV LCC 478 132 SOV LCD 427 80V HCC A 469 '414 SOV MCC B '476 161 SOV HCC C 474~ 248 SOV HCC D

• High side of current limiting reactor

• • Low - side of current limiting reactor

+ Viot on Unit /J4

+f- Bus voltage values not available

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Attachment C Page 1 of 2 CALCULATED BUS VOLTAGES UNIT //3

.Calculated Percent Error Bus Volta e 4KV Bus A>> -1. 3%.

4149'104 4KV Bus A>>>>

4KV Bus B>> 4142 -1.5%

4KV Bus B*>> 4115 4'80V LCA 462 -1.1%

480V LCB 468 -1.7%

480V LCC 467 -1.5%

480V LCD 457 -'2. 7%

480V 'MCC A 460 -0.3%

480V MCC B 464 480V MCC C 465 480V MCC D 4'46 T -3. 0%

• High side of current limiting reactor

• • Low side of current 1'imiting reactor

++ Bus measured values not available'

~w Attachment C Page 2 of 2 CALCULATED BUS VOLTAGES UNIT f34 4KV Bus A*

Calculated Bus V~olta e 4164 Percent Error From Measured

-1.8%

Volt ~

4KV Bus A** 4129 4KV Bus B>> 4133 -1.1%

4KV Bus B>>* 4102 480V LCA 466 -1.7%

480V L'CB 469 -2. 0%.

480V LCC 471 480V LCD '464 480V MCC A 463 -1.3%

480V MCC B 467 -1.8%

480V MCC C -1.2,%

'480V MCC D

• High side of current limiting reactor

>>* Low side of current limiting reactor

+ Not on Unit 84

~ Bus measured values not available

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