IR 05000309/1988163

Mgt Meeting 50-309/88-163 on 881018.Major Areas Discussed: Offsite Power Issues & Breaker Interrupting Capacity at Plant.Meeting Agenda & Handout Encl

ML20196E636
Person / Time
Site:	Maine Yankee
Issue date:	11/28/1988
From:	Durr J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
To:
Shared Package
ML20196E634	List: IR 05000309/1988163 ML20196E629
References
50-309-88-163, NUDOCS 8812120049
Download: ML20196E636 (19)

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U.S. Nuclear Regulatory Commission Region I Meeting No. 83-163 Docket N License No. OPR-36 Licensee: Maine Yankee Atcmic Power Company Facility Name: Maine Yankee Meeting At: NRC Region I, King of Prussia, Pennsylvania Meeting Date: October 13, 1953 Approved by: e M N Y 3. Ourr, Chief, Engineering Br4 .,' date

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Division of Reactor Safety Meeting Summary: Management meeting to discuss power distribution issues such as offsite power reliability and breaker interrupting capacity at Maine Yanke FDR ADOCK 05000309 Q FDC

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f Details i Attendees [ l Maine Yankee  ; i J. Randaua, President and Chief Executive Officer J. Garrity, Vice President Quality Programs and Engineering  ! G. Whittier, Manager, Nuclear Engineering and Licensing  ! F. Baxter, YAEC - Lead Electrical Engineer ' P. Anderson, YAEC - Project Manager from Maine Yankee ( Stone and Webster Engineering Corporation  ! t

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M. Robinson, Engineer Central Maine Power i i R. Conent. Electrical Engineer j t Nuclear Regulatory Commission 7 T. Martin, Director, Division of Reactor Safety l W. Johnston, Deputy Director. Division of Reactor Safety . R. Wessman, Project Director 1-3, NRR P. Sears, Project Manager, NRR  ! L. Marsh, Acting Chief. Engineering Branch  ! 0. Tondi, Section Chief, SELB, NRR i C. Holden, Sr. Resident i L. Td pp, Chief RPS 3A t C. Morris, Sr. Engineer, SELB, NRR l T. Kosby, Sr. Engineer, DRS C. Anderson, Chief Plant Systems Section ( Licensee Presentation f The purpose of this meeting was to discuss offsite power issues and breaker interrupting capacity at Maine Yankee. A copy of the meeting  : agenda is provided as Attachment A to this report. The licensee's presen- [ tation is outlined in their handout which is provided as Attachment 6 to l this repor ; The licensee described their offsite power sources which consist of the  ! Mason 115 Ky line and the Surowick 115 KV lin They stated that r operating experience with those lines, since 1972, demonstrates a high I record of availabilit The Maine Yankee (MY) offsite power sources were discusseo in consideration of 10 CFR 50, Appendix A, GDC 17 design criteria , for offsite po er sources, to demonstrate that the MY design features I compare favorably with the criteri l i i i _ _ . .

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i l l The !!censee discussed degraded power conditions on the Surowick line and  ; the status of their pl.as to install a capacitor bank to correct potential i low voltage conditions at the plant when this line is used. The licensee i plans to perform a periodic (i.e., every two years) reassessment of load l growth on the 115 Ky lines to project the acceptability of the quality of i these lines in the futur , l The reliability of the Mason line as an offsite power source was  ; discussed in consideration of the main transformer failures at MY in 1978 . and 1988. During each of these events, the transformer failures caused 4 i fault cordition which resulted in a momentary voltage dip, This condition  ! temporarily prevented a fast transfer from the unit auxiliary transformer  : to the offsite power tource. The licensee concluded that this condition t

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was the result of the 115 Ky Mason line sensing the MY main transformer . fault condition through the plant outgoing 345 Kv line. Since the 115 Ky [ Mason line and the 345 Ky lines are tied in at a location approximately  ! six miles distan'. from MY, the Mason line sensed the fault cordition before the transformer fault was cleared. The licensee stated that the i main transformer faults that occurred in 1973 and 1938 resulted from a i problem in the transformer involving a coil clamping deficiency. They plan to correct this deficiency in each of the two main transformers to improve the transformer reliability. This should remove the initiating event which led to the inability of the plant in 19/3 and 1983 to fast transfer from the onsite auxiliary transformers to the off-site power sourC The licensee briefly discussed the interrupting capacity of the 6.9 Kv and 4.16 Ky breakers and station plans to accc-*odate a station blackout even . Conclusion The NRC staff stated that they plan further review of the capacitor bank modification and the basis for the interrupting capacity of the in-plant 6.9 Ky and 4.16 Ky breaker In additien, the staff stated that further NRC review is planned for the MY fast transfer capability to the 115 Kv off-site power source The relatively close (6 miles) tie of the 115 Kv Mason line to the plant outgoing 345 KV line appears to affect the short term availability of the Mason line when significant fault conditions occur on the 345 Kv lin ,____-________________-. '

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I Technical Presentation F. D. Baxter [

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      , Description of transmission and utL11ty interconnections with Natue Yankee (FSAR, Figure 8.2-1).

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      > Description of Auxiliary power System (FSAR, Figure 8.3-1).  ' Power flow during normal plant operatio . Power flow during startup and plant trip ; Fast transfer schem I Operating experience with 115 kV lines since 197 l r

Mason Eurowiec Both Lines { Total Line Outages (Hours) 554 2,952 l Planned Outages (Hours) 550 2.924 0 l Unplanned outages (Hours) 4 28 ! l Low voltage event [ Recorded Date Plant status Mason surewise voltana conclusion f I 12/14/82 Startup out In-Service 109 kV Low Voltage ! Incident 7/18/86 Startup Out In-Service 113 kV Prealarm Only [ t Improvements subsequent to 1982 inciden I l

 (a) Reconductoring of Surowiec lin !
 (b) Transformer tap change f f Actions subsequent to 1986 inciden l

 (a) Reanalysis and revision of voltage study,   f
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 (b) Conclusion that Surowiec line is unable to support worst case loadin . Other issue (a) Transformer faul I i
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', ,. 6 ,' b Technical Presentation (Continued) F. D. Baxter (c) Transformer fault,and effect on the Surowiec line with capacitor ban (d) Long-term plans to maintain adequacy of the Surowiec lin (e) Short circuit interrupting capability of 6.9 kV and 4.16 kV switchgea (f) Station Blackou .

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CAPACITOR BANK R. L. CONANT ' CMP PROJECT ENGINEER DESIGN OBJECTIVES

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IMPROVE VOLTAGE REGULATION ADD LOAD REACTIVE COMPENSATI0tt [ AUTOMATIC CONTROL ENGINEERING STUDIES l STEADY STATE TRANSIENT STATE l DYNAMIC STATE , EQUIPMENT SPECIFICATION , EQUIPMQ{I l CAPACITOR BANK I ARRESTER CURRENT LIMITING REACTOR , i CIRCUIT BREAKER t i DISCONNECT SWITCH - CONTROL PANEL i

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MAINE YANKEE CAPACITOR BANK EQUIPMEIR

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ATTACHMENT A

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MAINE YANKEE OFF-SITE POWER i

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OCTOBER 18, 1988  ! I c-  ! INTRODUCTION G. D. WHITTIER [

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BACKGROUND F. D. BAXTER Orr$1TE POWER DESIGN , j OPERATING EXPERIENCE i i

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SUROWIEC 115 KV LINE F. D. BAXTER i i OPERATING EXPERIENCE [

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CURRENT ASSESSMENT  ! CAPACITOR BANK R. CONANT DESIGN STATUS PERIODIC REASSESSMENT J. H. GARRITY OTHER ISSUES F. D. BAXTER TRANSFORMER FAULT EVENT DESCRIPTION AUTO TRANSFER LOGIC

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ON SITF STUDIES STATION ELACKOUT PLANS C0i1CLUSION J. H. GARRITY 0548L-GDW

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POWER SCURCES

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345 KV 115 KV Mad 115 KV SUR0WIEC DG-1A DG-1B DG-2 0556L-GDW

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  .9 0FFSITE POWER DESIGN
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GENERATOR QUTPUT

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SAFETY AND NON-SAFETY (

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TWO 115 KV LINES

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SUR0WIEC AUTO BUS TRANSFER TO 115 KV ON FAILURE OF PREFERRED SOURCE .

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345KV-SWITCHYA'RDkND115KVSWITCHYARD - i !

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STATION SER VICE TRANS FOR M ER S

EM X-26 M AIN MN X-14

     "# X-24 # GENERATOR

- mm mu mn mm ' l l , s 4.16 K V 4.16 K V 6.9 K V 4.16 K V 6. 9 K V

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0FF SITE POWER AVAILABILITY

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SOURCE AVAILABILITY l 345 KV 100% > MASON 115 KV 99.6% SUR0WIEC 115 KV 98.4%  !

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115 KV 99.997% l

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PLANT RESPONSE

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345 KV M/S MY RESPONSE GENERIC RESPONSE

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U U/U NORMAL OPERATION NORMAL OPERATION U U/D NOP'AL OPERATION POSSIBLE TRIP l U D/U NORMAL OPERATION POSSIBLE TRIP  ; l U D/D NORMAL OPERATION PROBABLE TRIP i

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D U/U NORMAL TRIP POSSIBLE LOAC D U/D NORMAL TRIP POSSIBLE LOAC

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D D/U NORMAL TRIP POSSIBLE LOAC D D/D LOAC LOAC

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COMPARISON WITH GDC 17

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DESIGN FEATURE GDC 17 MY DESIGN

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OFF SITE POWER SOURCES 2 3'

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SWITCHYARDS 1 2 INDEPENDENCE OF NOT INDEPENDENT SWITCHYARDS ADDRESSED diT0MATIC TRANSFER NOT REQUIRED ABT FOR SAFETY ; AND NON-SAFETY < IMMEDIATELY AVAILABLE 1 2 i i

DELAYED AVAILABILITY 1

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i e MAINE YANKEE OFF SITE POWER DESIGN EXCEEDS REGULATORY REQUIREMENTS

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MAINE YANKEE OFF SITE RELIABILITY BETTER THAN AVERAGE ON SITE EMERGENCY POWER DESIGN EXCEEDS REGULATORY REQUIREMENTS ON SITE EMERGENCY POWER RELIABILITY - BETTER THAN AVERAGE 0556L-GDW }}