ML20086B033

Submits Suppl Info Re 950203 Proposed TS Concerning 4 Kv Loss of Voltage & Degraded Voltage Conditions Tables 3.3-3, 3.3-4,3.3.5 & 4.3-2

ML20086B033
Person / Time
Site:	McGuire
Issue date:	06/14/1995
From:	Mcmeekin T DUKE POWER CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
Shared Package
ML20086B035	List: ML20086B033 ML20086B075
References
NUDOCS 9507050140
Download: ML20086B033 (6)

Text

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' DukeIbicer Cornpany - T.C Alchlan a

kicGuire Nuclear Generation Department . VicePresident 12700HagersfenyRoad(klGOlW) (704)8754800 JIuntersville,NC2807&&985 . (7D4)8754809 Fax

. DUKEPOWER L

_ June 14, 1995.

U.S. Nuclear Regulatory Commission

-Attention: Document Control' Desk Washington, D.C. 20555

Subject:

McGuire Nuclear Station, Units-l~and 2 Docket Nos. 50-369 and 50-370 Supplemental Information Relating to Proposed Technical' Specification Amendment Submittal 9/28/94 4 kV Loss of Voltage and Degraded Voltage Conditions Tables 3.3-3, 3.3-4, 3.3.5, and 4.3-2

Dear Sir:

By letter dated 5/3/95, we responded to your Request For-Additional Information dated 2/3/95'regarding the subject given above. During a telephone conversation with us on 5/25/95, your staff requested additional information regarding two items (items 7 and 11) explained in our letter dated 5/3/95 above.

Attachment 1 includes our response to these two items.

Attachment'2-includes our up-to-date proposed Technical.

Specification pages.

Please contact P. T. Vu of McGuire Regulatory Compliance group at (704) 875-4302 if there are any questions regarding this additional information.

Very truly yours, KDI T.'C. McMeekin Attachments 3000S4 _

95070 DR Q h hPDR 69 I Lt m.

p1 U.S. NR June 14, 1995- -

Page 2 Xc: (with all attachments)

Mr. S.D. Ebneter Administrator, Region-II U.S. Nuclear Regulatory Commission .

101 Marietta St., NW, Suite 2900 -

Atlanta,-GA. 30323 [

Mr. V. Nerses Office of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 9H3 Washington, D.C. 20555 Mr. G.-Maxwell NRC Resident Inspector McGuire Nuclear Station Mr. Dayne Brown, Chief Division of' Radiation Protection P.O. Box 27687-Raleigh, N.C. 27611-7687 I

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U.S. NRU June 14, 1995

Page'3 bxc: ..(with all attachments)

[- A.V. Carr (PB05B)

G . A '. Copp (EC05N) l; -D. Jamil (MG01EE) l W.N. Matthews (MG01EE)-

A.C. Williams (MG01EE)  :

MNS.RGC Tech. Spec. Subject File-l 1

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ADDITIONAL RESPONSE 1

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, I U.S. NRC Attachment 1 June 14, 1995 Page 1 l

7. Provide a discussion that contains information demonstrating j that the maximum of a 600 second time delay without a concurrent safety injection signal ensures that all connected Class 1E loads are not damaged and will not trip for voltages that could exist down to a level just above the i loss of voltage setpoint.  :

1 The 600 second time limit acknowledges that loads cannot be operated continuously below the dropout setpoint and gives the operator time to improve voltage before transferring to the alternate source. Equipment will not be damaged and no appreciable reduction in service life will result from operation of such a short duration. Some of the loads ,

required for Safety Injection are not normally connected to  ;

the power system, so they would not be exposed to the lower voltage during this period. If a Safety Injection signal is received, the 4kV system will separate from offsite power before mitigation loads are added to the system.

Part of the McGuire design philosophy is to provide safety related motor loads with long time overcurrent protection ,

set to 150% of the rated full load amperes and below the motor damage curve. This provides enough margin to allow motors to operate at the degraded voltage setpoint for 600 t seconds without damage.

t It is preferable to make all attempts to improve the offsite voltage rather than send the plant through a loss of power ,

transient on the 4kV system. Before the degraded voltage is sensed at the plant, the Transmission Control Center (TCC) will already be taking action to improve grid voltage because it will be below the normal operating range. The l TCC has specific guidance on the voltage requirements for  ;

the plant and pre-determined contingency plans on how to maintain those values. This information is kept in a manual on the TCC console for use by the operators. Part of the contingencies is to start Cowans Ford Hydroelectric Station >

which is connected directly to the plant switchyard. This station takes approximately 6 minutes to come on-line. .

f Past performance has demonstrated that standard operating requirements have been successful in maintaining adequate i switchyard voltages. There is more than 5% margin between  ;

the normal operating voltage and the highest degraded voltage setpoint plus channel uncertainty. These operating ,

requirements have been reviewed and accepted during both the i EDSFI and Generic Letter 89-10 audits. Once the degraded '

voltage relays actuate, it is not expected that the voltage would be rapidly decaying because of the compensatory measures taken by the TCC in conjunction with the plant l l

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U.S. NRC Attachment 1 June 14, 1995 Page 2 i I

l operators. If it were a more serious collapse of the grid  !

and the voltage was dropping rapidly, the loss of voltage relays would activate prior to the completion of the 600 second timer. Thus the electrical system relay design provides adequate protection against both loss of voltage  !

and degraded voltage situations and will prevent any damage to Class lE loads.

11. Provide a technical discussion to address why the setpoint for the first level of undervoltage protection can be less than or equal the value instead of greater than or equal.

The current technical specification setting addresses loss of voltage and degraded voltage concerns, therefore,it specifies a minimum setting. The new loss of voltage setting has a single purpose and is based on the worst voltage dip imposed on the system. Providing an upward limit and setting the relay below the worst case dip reduces time delays and inadvertent actuation resulting from >

transients. The relay cannot be set as low as 0 VAC because the setpoint basis is the worst voltage dip minus the relay channel uncertainty. This places the relay setting just .

below the minimum expected voltage on the auxiliary system.

In order to assure a minimum setting, the trip setpoint will be changed from the proposed 5 3220V for Unit 1 to 3174 i 45 VAC and 5 3202.5V for Unit 2 to 3157 i 45 VAC. This tolerance envelops the expected variance of the relay setting as defined in calculation MCC-1381.05-00-0094. The allowable value will be changed from the proposed s 3227V for Unit 1 to 2 3122V and s 3206V for Unit 2 to 2 3108V.

The allowable value is equal to the relay pickup setting minus the channel uncertainty as defined in calculation MCC-1381.05-00-0094.

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