ML18019A500

Forwards Addl Info Re Adequacy of Station Electrical Distribution Sys Voltage,In Response to SER Confirmatory Item 19 & Responses to Power Sys Branch Questions.W/O Encls

ML18019A500
Person / Time
Site:	Harris
Issue date:	12/23/1985
From:	Zimmerman S CAROLINA POWER & LIGHT CO.
To:	Harold Denton Office of Nuclear Reactor Regulation
References
NLS-85-421, NUDOCS 8512310239
Download: ML18019A500 (10)

Text

REGULATORY NFORMATION DISTRIBUTION S EM (RIDS)

ACCESSI(>14 NBR: 8512310239 DOC. DATE: 85/12/23 NOTARIZED: NO DOCKET ¹ FAGIL: 50-400 Shearon Harv is Nucleav Power Plant> Unit 1> Cav olina 05000400 AUTH. NAME AUTHOR AFFILIATION ZIMMERMAN>S. R. Carolina Pover & Light Co.

REC IP. NAME REC I P IENT *FF ILI ATION DENTON> H. R. Office of Nucleav Reactov Regulation> Director (post 851125

SUBJECT:

Forwards addi info v e adequacy of station electv ical distribution sos voltage> in v esponse to SER Confirmatory Item 19 & responses 'to Potuer Sgs Branch questions. W/o encls.

.,DIBTR IBUTION CODE: BCOID COPIEB RECEIVED: LTR i ENCL l B12E:

TITLE: Licevvsing Submittal: PSAR/FSAR Amdts & Related Cov respondence NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PWR-* ADTS 1 1 PWR-A PD2 PD 1 1 PWR-A EB 1 1 PWR-A EICSB 1 1 PWR-* FOB 1 1 PWR-A PD2 LA 1 1 BUCKLEY> B 01 2 2 PWR-A PSB 1 1, PWR-A RSB 1 1 INTERNAL: ACRS 41 '6 6 ADM/LFMB 1 0 ELD/HDSi 11 0 IE FILE IE/DEPER/EPB 36 1 1 IE/DGAVT/GAB 21 1 NRR BWR *DTS 1 0 NRR PWR-A ADTS 1 0 NRR PWR-B ADTS 1 0 NRR ROE> M. L 1 1 NRR/DHFT/HFIB 1 1 NRR/DHFT/MTB SRO DIR 1 0 NRR/DSRO/RRAB 1 1 FL 04 1 RGN2 3 3 AMI/MIB 1 0 EXTERNAL: 24X 1 BNL(AMDTS ONLY)

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Carolina Power 8 Light Company DEC 2 3 1985 SERIAL: NLS-85-021 Mr. Harold R. Denton, Director Office'of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Washington, DC 20555 SHEARON HARRIS NUCLEAR POWER PLANT UNIT NO. l - DOCKET NO.50-000 ADEQUACY OF STATION ELECTRICAL DISTRIBUTION SYSTEM VOLTAGES

Dear Mr. Denton:

Carolina Power dc Light Company hereby submits additional information concerning adequacy of station electrical distribution system voltages at the Shearon Harris Nuclear Power Plant. The attached information is submitted in response to Safety Evaluation Report Confirmatory Item No. l9 and responds to specific questions from the Power Systems Branch.

If you have additional questions or require further information, please contact me.

Yours very truly, S. R. Zimmerman Manager Nuclear Licensing Section 3HE/ccc (30093HE)

Attachment CC: Mr. B. C. Buckley (NRC) Mr. H. A. Cole Mr. O. Chopra (NRC-PSB) Mr. Wells Eddleman Mr. G. F. Mavweli (NRC-SHNPP) Mr. 3ohn D. Runkle Dr. 3. Nelson Grace (NRC-Rll) Dr. Richard D. Wilson Mr. Travis Payne (KUDZU) Mr. G. O. Bright (ASLB)

Mr. Daniel F. Read (CHANGE/ELP) Dr. 3. H. Carpenter (ASLB)

Wake County Public Library Mr. 3. L. Kelley (ASLB) g~/ Cb'~+~

/g 411 Fayeneviae Streel ~ P. O. Box 1551 ~ Raleigh. N. C. 27602

SHEARON HARRIS NUCLEAR POWER PLANT SER CONFIRMATORY ITEM NO. I9 FOLLOW UP ITEM I Show how the degraded voltage relays protect the motors in the band from 7396 of bus rated voltage to 7596 of motor rated terminal voltage for their one minute rating.

RESPONSE

The purpose of the first level of undervoltage relays (Devices 27-l, 27-2, and 27-3) is to detect loss of offsite power at the Class lE buses. These relays upon sensing a loss of voltage, automatically disconnect the offsite source from the Class IE bus, initiate load shedding and start the diesel generator as described in FSAR Section 8.3.l.l.2.8. Once the loading of the diesel generator has begun, operation of the undervoltage relays is blocked until the Class IE bus is re-synchronized to an offsite source by closing the bus tie breakers.

Low voltage encountered while the motors are running will result in higher than normal operating currents, and in the case of induction motors result in increased heating on the stator winding. Protection against overheating is adequately provided by overload relays located in each individual Class IE motor circuit. Thus, setting the loss of offsite power relays to protect the motors for overloads caused by low voltage is neither necessary nor required by PSB-I. Any motor overlapping protection provided by these relays is an ancillary benefit of their primary function.

Although it is our position that the loss of offsite power relays are not needed nor required to provide motor protection, in practice they do, in fact, overlap the 6900 volt system. The loss of offsite power relays are set at 7396 of rated bus voltage (6900 V).

This setting is a conservative choice when compared with the generally accepted setting range of 70% or less of rated bus voltage as referenced in the background section of the BTP, PSB-I document. This setting in effect limits the 6.9kV motor operation to 75.8%

of motor rated voltage (6600 V) (after taking into consideration a 0.596 voltage drop between the 6.9kV bus and the motor terminals). Effective (and overlapping) motor protection is provided in this case.

(3049 J DK/ccc )

SHEARON HARRIS NUCLEAR POWER PLANT SER CONFIRMATORY ITEM NO. I9 FOLLOW UP ITEM 2 Did CPRL follow through the difference between PSB-I report and the SER?

RESPONSE

FSAR paragraph 8.3.1.1.2.8 states that the load shedding relays are blocked upon initiation of DG load sequence action. This paragraph agrees with the PSB-I report. No commitment is made in either document to reinstate the relays after sequencing on the DG's is completed.

SER paragraph 84.2.2 is entitled "Position 2 - Interaction on Onsite Power Sources with the Load Shedding Feature" (emphasis added). Position 2 of BTP PSB-I was only intended to discuss interaction of sequencing on the offsite power supply. CPdcL recommends that SER paragraph 8.0.2.2 be retitled and that the first paragraph thereunder be deleted.

(3049JDK/ccc )

SHEARON HARRIS NUCLEAR POWER PLANT SER CONFIRMATORY ITEM NO. I9 FOLLOW UP ITEM 3 Verify pickup of 27-l, 2, 3 BU/SA is lower than 27-l, etc.

RESPONSE

The function of the 27 BU (Back-Up) relays is to permit undervoltage testing of the loss of voltage relays. This is performed by a permissive to the test relays which simulate the loss of voltage and block the actual tripping of the buses. Should the 27 BU relays not pickup, the test function is not permitted; should the 27 BU relays prematurely dropout, the normal function is reinstated. Therefore, the actual performance characteristics of the relays do not affect the normal operation of the loss of voltage relays.

(3049iOK/ccc )

SHEARON HARRIS NUCLEAR POWER PLANT SER CONFIRMATORY ITEM NO. l9 FOLLOW UP ITEM 0 a) Did CPRL start the largest load after the other loads were sequenced on DG?

b) Did CPRL check dropout of MCC coils on starters at 080V on DG sequence?

RESPONSE

a) No, CPRL did not remove and re-start the largest motor load after other loads were sequenced onto the DG. The largest motor load is the l300 hp, Emergency 'service Water Pump, which is normally sequenced on Block No. 3.

b) Yes, CPRL did check the dropout of the 080V starters during the voltage drop caused by Block No. 1 (minimum voltage of 80.0% of rated voltage). The most sensitive Gould starters are NEMA Size 3 and 0 which have a maximum dropout voltage of 06% of rated system voltage.

(3049JDK/ccc)

SHEARON HARRIS NUCLEAR POWER PLANT SER CONFIRMATORY ITEM NO. I9 FOLLOW UP ITEM 5 Modify Sketch SK-E-552, Sheet 2 for auxiliary transformer to correct typographical error.

RESPONSE

In Revision 3 of the PSB-I report (attached), Sketch SK-E-552, Sheet 2 of 2 has been revised to show the unit auxiliary transformer correctly labeled.

(3049JDK/ccc )

SHEARON HARRIS NUCLEAR POWER PLANT SER CONFIRMATORY ITEM NO. I9 FOLLOW UP ITEM 6 Expand the discussion of Position 0 - Voltage Level Optimization (Test Method).

RESPONSE

As suggested by the NRC reviewer, an expanded and more detailed discussion of Position 0 has been incorporated in Revision 3 of the PSB-I report (attached).

(3049 JOK/ccc )