ML20041D233

Adequacy of Station Electric Distribution Sys Voltages, Edwin I. Hatch Nuclear Power Plant,Units 1 & 2, Informal Rept

ML20041D233
Person / Time
Site:	Hatch
Issue date:	01/31/1982
From:	Udy A EG&G, INC.
To:	Prevatte R Office of Nuclear Reactor Regulation
References
CON-FIN-A-6429 EGG-EA-5369, NUDOCS 8203040602
Download: ML20041D233 (11)

Text

_ _ _ _ _ _ _ . . _ - - -

EGG-EA-5369, Rev. 1 January 1982 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM gg VOLTAGES, EDWIN I. HATCH NUCLEAR POWER PLANT, *

• MS/O s O f(S UNIT N05. 1 AND 2 RECEgygn } &-

t MilR og 1982s  :

%x -9 4

A. C. Udy 1 4s DD e

/e #

yge N et. f' .hi U.S. Department of Energy Idaho Operations Office = idaho National Engineering Laboratory 3 s t' m : .c u" \ M3d iN . t d

9 EM amer:-c5 %

5 seg .

- M. e s .

c,. .., - -

y+ 2 J M k e v :h :--.-. w tlE l % Ad4 m +- m . . th M g 4 s

m~,;:

er

[ Ndk %. 1n" ran C k hr**e--r ~ = (-- e M P C - [$ ,

m._ _f._.gy . ,

^-^

. q [4 T,5 h'

'N.N. .

s .-

yg j

^

c '*p

, . . 4M cwa i[twiibik,id This is an informal report intended for use as a preliminary or working document Prepared for the U.S. Nuclear Regulatory Comission Under DOE Contract No. DE-AC07-76ID01570 g FIN No. A6429 E G g G ie,no 8203040602 820131 PDR RES 8203040602 PDR

h EGnG... . ,-

FORM EG4G 398

' " ~ " "

INTERIM REPORT Accessic , No.

Report No. EGG-EA-5369. Rev. 1

. Contract Program or Project

Title:

Selected Operating Reactor Issues Program (III)

Subject of this Document:

Adequacy of Station Electric Distribution System Voltages, Edwin I. Hatch Nuclear Power Plant, Unit Nos. I and 2 Type of Document:

Informal report Author (s):

A . C . 'Jdy Date of Document:

January 1982 Responsible NRCIDOE Individual and NRCIDOE Office or Division:

R. L. Prevatte, Division of Systems Integration, NRC This document was prepared primarily for preliminary orinternal use. it has not received full review and approval. Since there may be substantive changes, this document should not be considered final.

EG&G Idaho. Inc.

Idaho Falls. Idaho 83415 P

Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C.

Under DOE Contract No. DE-AC07-76tD0tS70 NRC FIN No. A6429 INTERIM REPORT

0253J 4+

ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES EDWIN I. HATCH NUCLEAR POWER PLANT, UNIT NOS. 1 AND 2 January 1982 A. C. Udy Reliability and Statistics Branch Engineering Analysis Division EG&G Idaho, Inc.

r TAC Nos. 12831 and 12832 Docket Nos. 50-321 and 50-366

. .. -- .- . . . . - . - . _ --_ _. . _ ~ . - - _

L I

\

s ABSTRACT This EG&G Idaho, Inc. report reviews the capacity and the capability of the onsite distribution system at the Edwin I. Hatch Nuclear Power

,i Plant, in conjunction with the offsite power sources, to automatically

, start and continuously operate all required safety loads. ,

FOREWORD i

This report is supplied as part of the " Selected Operating Reactor i

Issues Program (III)," oeing conducted for the U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation,xDivision of Licensing, by EG&G Idaho, Inc., Reliability and Statistics Branch.

i The U.S. Nuclear Regulatory Commission funded the work under the ,

authorization, B&R 20 19 01 06, FIN A6429. .

i s

?

4 l

i 11 ,

-op- - -

CONTENTS 1

1.0 INTRODUCTION

2.0 DESIGN BASIS CRITERIA ........................................... 1 N. ,

2 3.0 SYSTEM'0ESCRIPTION ..............................................

2 4

4.0 ANALYSIS DESCRIPTION ............................................

2 4.1 Design Changes ............................................

2 4.2 Analysis Conditions .......................................

5 4.3 Analysis Results ..........................................

5 4.4 Analysis Verification .....................................

5 5.0 EVALUATION ......................................................

6

6.0 CONCLUSION

S .....................................................

7

7.0 REFERENCES

FIGURE Hatch Station Unit One Line Diagram . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3 1.

TABLE

1. Edwin 1. Hatch Nuclear Power Station Class lE Equipment Voltage Ratings and Worst Case Load Terminal Voltages ............................... 4 6

iii  !

l

.)'

_.. a *. . - . ,

ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES EDWIN I. HATCH NUCLEAR P)WER PLANT, UNIT NOS.1 AND 2 r

1.0 INTRODUCTION

An event at the Arkansas Nuclear One station on September 16, 1978 is described in NRC IE Information Notice No. 79-04. As a result of this event, station conformance to General Design Criteria (GDC) 17 is being questioned at all nuclear power stations. The NRC, in the generic letter ofAuguyt8,1979,"AdequacyofStationElectricDistributionSystemsVolt-

• - ages," required each licensee to confirm, by analysis, the adequacy of the voltage at the Class lE loads. This letter included 13 specific guide-lines to be followed in determining if the voltage is adequate to start and continuously operate the Class lE loads.

The Georgia Decemger7,1979.{owerCompany(GPC)respondedwithanana Besides the original anal.vsis, a letter of Jul 22, 1977, the Final Safety Anal submitted on April 28,198g,ysis Report were reviewed (FSAR),

for this and additional an report. Telephone conversations in June 1980 clarified portions of the April 28, 1980, submittal. These conversa mitted on Octoger 9,1980.gions MCC contactorresulted insupplied ratings were additional in material b February 1981, and in a letter dated January 12, 1982 8 Based on the information supplied by GPC, this report addresses the capacity and capability of the onsite distribution system of the Edwin I. Hatch Nuclear Power Plant, in conjunction with the offsite power system, to maintain the voltage for the required Class 1E equipment within acceptable limits for the worst-case starting and load conditions.

The following description and evaluation of the Unit 1 design also applies to the onsite distribution system of Unit 2.

2.0 DESIGN BASIS CRITERIA The positions applied in determining the acceptability of the offsite voltage conditions in supplying power to equipment are derived from the following:

1. General Design Criterion 17 (GDC 17), " Electrical Power Systems," of Appendix A, " General Design Criteria for I

Nuclear Power Plants," of 10 CFR 50

2. General Design Criterion 5 (GDC 5), " Sharing of Struc-l - tures, Systems, and Components," of Appendix A, " General i Design Criteria for Nuclear Power Plants," of 10 CFR 50

3. IEEE Standard 279-1971, " Criteria for Protection bys-l tems for Nuclear Power Generating Stations"

4. IEEE Standard 308-1974, " Class lE Power Systems for Nuclear Power Generating Stations" l'

5. Staff positions as detailed in 4 letter sent to the licensee, dated August 8, 1979.'

yixreviewpositionshavebeenestablishedfromtheNRCanalysisguide-and the above-listed documents. These positions are given in lines Section 5 of this report.

3.0 SYSTEM DESCRIPTION Figure 1 is a simplified sketch of the unit one-line diagram taken from Sheets 5-60 and 5-61 of the Reference 2 attachments. The distribution .-

systems for Unit I and Unit 2 are identical. The Unit 1 Class lE 4160V buses can be supplied offsite power from tne 230kV switchyard by startup "

transformers 1C or 10. These buses cannot be connected to the unit auxili-ary transformers lA or 18.

The two Class lE 600V buses IC and ID are each normally cornectert by 4160/600V transformers to Class lE 4160V buses 1E and 1G, respectively. An identical 4160/600V transformer, connected to Class 1E 4160V bus IF can be connected to either 600V bus 1C or 1D by disconnect links. Procedures prevent both 600V buses being connected to the same transformer or being operated in parallel. Class lE buses 1C and 1D supply essential power to the 120/208V AC instrument power system by two separate transformers.

The GPC su ofthisreportgpliedtheequipmentoperatingrangesidentifiedinTable1 4.0 ANALYSIS DESCRIPTION _

4.1 Design Ghanges. The GPC has changed the tap settings to 0.925 pu

( instead of 1.00)* 3 on all of the Hatch Station transformers that supply voltages of less than 600V.

4.2 Analysis Conditions. The GPC has determined by load-flow and grid contingency studies that the maximum expected offsite grid voltage is 239.2kV (104%) and that the minimum is 225.4kV (98%).

The GPC has analyzed each offsite sourcc to the onsite distribution system under extremes of load and offsite voltage conditions to determine the terminal voltages to the Class lE equipment. The worst case Class lE equipment terminal voltages occur with start-up transformer 1D supplying

, power to the Unit 1 Class lE buses (transformer 20 for Unit 2)5 under the following conditions:

t 1. The GPC determined the maximum expected bus and load i voltages using the maximum expected grid voltage with one unit operating and the other unit shutdown. The unit loads reflect the operating or shutdown status of the unit.

2. The GPC determined the minimum expected continuous bus and load voltages using the minimum expected grid voltages, and with one unit in normal shutdown and one unit in a LOCA condition and all buses in service.

2 o - -

j

Unit Gen 230 KV SWITCHYARD (UNIT 1)

1. j 500 KV SWITCHYARD (UNIT 2)

VIA MAIN TRANSFORMER s 230 KV SWITCHYARD 1B 1C 1A 10 ^

.. TOR mT CQ r1 CQ rQ

[] []

BUS lA b [] BUS IB

[] []

BUS 1C

[] []

BUS 1D 4160V 4160V 4160V 4160V DG DG DG 1A 1B 1C s TO BUS

[x] [] [] [x] C 2F gg BUS lE BUS 1F BUS 1G 4160V 4160V 4160V CLASS 1E CLASS lE CLASS 1E x _X_

us UV La S sic S SIC D SS10 PG Pn nq

_ _L 1 __

x x BUS 1C BUS 1D 600V 600V CLASS-lE CLASS 1E

1. UNIT 2 IDENTICAL ExCEPT i FOR SHARED D-G SET 1B

2. BREAKERS SHOWN ALIGNED HATCH STATION FOR PREFERRED OFFSITE UNIT ONE LINE DIAGRAM SOURCE TO CLASS lE BUSES FIGURE 1 3

l l

1 TABLE 1 CLASS lE EQUIPMENT VOLTAGE RATINGS AND ANALYZED WORST CASE TERMINAL VOLTAGES

(% of nominal voltage)

Maximum Minimum Analyzed Equipment Condition Rated Analyzed Rated Steady State Transient , ,

8 4000V Motors Start -- -- 75/70 -- 75.6 Operate 110 107.8 90 91.4 - -.

3 550V Motors Start -- --

75/70 -- 75.1 Operate 110 110.0 90 92.0 --

600V MCC Pickup -- -- 74.8 -- 68.9 contactors Dropout -- -- 54.8 -- 68.9 (ll5V coil) Operate 108.7 100.8 85 85.4 --

a 208r Motors Start -- --

75/70 -- 71.2 Operate 110 108.8 90 90.4 --

208V MCC Pickup -- -- 74.8 -- 72.6 contactors Dropout -- --

54.8 -- 72.6 (ll5V coil) Operate 108.7 108.8 85 91.4 --

Low voltage instruments and u tgol circuits

a. 30-second stall rating,

b. GPC states4 , "The buses may supply instruments and control circuits as required by GDC 13. We do not know of any connected equipment which is not capable of withstanding the analyzed voltages. However, not all manufacturers' responses are yet available. If any equipment is dis-covered which does not meet the functional requirements in the expected conditions, it will be the subject of a report to the NRC."

i

3. The GPC determined the minimum expected transient bus and load voltages immediately prior to the minimum '

expected continuous voltages (above) due to the automatic and simultaneous start of the Class lE loads and a condensate pump, in one unit.

These conditions are the worst of those supplied by the GPC submittals. '

The voltage levels supplied for analyses using transformer 1C assumed that buses lA and IB are not transferred from onsite power (transformer 18) to transformer 1C on a unit trip. Interlocks prevent this transfer.

4

4.3 Analysis Results. Table 1 shows the projected worst case Class lE equipment terminal voltages. It shows tnat, in all steady-state cases, the Class lE loads have voltages that are within the equipment rated limits.

The duration of the worst case transient voltage condition will be less than 12 seconds before normal operating voltages are restored. During this time, no contactors will drop out and no spurious tripping of loads will occur. The 208V motors are not capable of starting at the voltages analyzed during this transient, however, they will start on voltage recovery above 75%. During the analyzed transient of less than 12 seconds, s the voltage is maintained above the rated (70%) stall rating, so that no damage to these motors will occur.

" As stated in footnote b of Table 1 of this report, GPC has determined that the 120V AC instruments and control circuits are capable of with-standing the analyzed voltages.

4.4 Analysis Verification. The load flow analysis was verified4 by measuring the grid, generator and bus voltages, and the actual load of the buses and selected equipment while Unit 1 was operating and Unit 2 was in a normal shutdown. The analysis model was developed from this measured loading. The model was then used for the GPC analysis. An analysis was done using the measured generator and offsite source voltages, and the results compared with the measured bus voltages. The voltages analyzed for the measured load are within +0.58% of the duplicate measured bus voltages.

While GPC did not directly verify the analysis for buses at voltages less than 4160V, they did include the load measurements and system imped-ences in developing the model of the distribution system. In lumping the lower voltage bus loads on the 4160V bus base, the analysis verification does account for the low voltage buses.

5.0 EVALUATION Six review positions have been established from the NRC analysis guide-linesl and the documents listed in Section 2 of this report. Each review position is stated below, followed by the evaluation of the licensee submittals.

Position 1--With the minimum expected offsite grid voltage and maximum load condition, each offsite source and distribution system connection combination must be capable of starting and of continuously operating all Class lE equipment within the rated equipment voltages.

GPC has shown, by analysis, that the Hatch Station has sufficient ~

~

capability and capacity for starting and continuously operating all Class lE equipment within the equipment voltage ratings.

Position 2--With the maximum expected offsite grid voltage and minimum load condition, each offsite source and distribution system connection combination must be capable of continuously operating all Class 1E equip-ment without exceeding the rated equipment voltage.

5 t

GPC has shown, by analysis, that the voltage ratings of the Class lE equipment are not excceded.

Position 3--Loss of offsite power to either the redundant Class lE distribution systems or the individual Class lE loads, due to operation of voltage protection relays, must not occur when the offsite power source is within analyzed voltage limits.

EG&G Idaho, Inc., will verify in a separate report, that the require-ments of this position are satisfied (TAC No. 10026 and 11262). .

Position 4--Test results should verify the accuracy of the voltage -

analyses supplied.

GPC has supplied the required information2 which shows the analysis . .

to be an accurate representation of the worst case voltage conditions for the Class lE buses and loads.

Position 5--No event or condition should result in simultaneous or consequential loss of both required circuits to the offsite power network (GDC 17).

GPC has analyzed tne connections of the Hatch Station to the offsite power grid and has determined 2 that no potential exists for either a simultaneous or a consequential loss of both circuits from the offsite grid.

Position 6--As required by GDC 5, each offsite source shared between units in a multi-unit station must be capable of supplying adequate start-ing and operating voltage for all required Class lE loads with an accident in one unit and an orderly shutdown and cooldown in the remaining units.

Each unit is independently connected to offsite power and no common electrical connection exists between units; therefore, this position does not apply to the Hatch Station.

6.0 CONCLUSION

S The analyses submitted by the GPC for the Edwin I. Hatch Nuclear Power Plant were evaluated in Section 5.0 of this report. It was found that:

1. Voltages within the operating limits of the Class lE equipment are supplied for all projected combinations I of plant load and normal offsite power grid conditions; including an accident in one unit and the safe shutdown of the other unit.

2. The test used to verify the analysis shows that the t analysis is an accurate representation of the worst I case conditions analyzed. ,

3. The GPC has determined that no potential for either a simultanous or a consequential loss of both offsite power sources exists.

6 l

l EG&G Idaho, Inc., is performing a separate review of the undervoltage relay protection at the Edwin I. Hatch Nuclear Power Plant. This will l evaluate the relay setpoints and time delays to determine that spurious tripping of the Class 1E buses will not occur with normal offsite source voltages.

7.0 , REFERENCES

1. NRC letter, William Gammill, to All Power Reactor Licensees (Except Humboldt Bay), " Adequacy of Station Electric Distribution Systems Voltages," August 8, 1979.

2. GPC letter, R. J. Kelly, to U.S. Nuclear Regulatory Commission,

" Adequacy of Station Electric Distribution System Voltages," dated December 7, 1979.

3. GPC letter, Chas. F. Whitmer, to U.S. Nuclear Regulatory Commission,

" Emergency Power Systems," dated July 22, 1977.

4. GPC letter, W. A. Widner, to U.S. Nuclear Regulatory Commission,

" Adequacy of Station Electric Distribution System Voltages," dated April 28, 1980.

5. Telecons, D. Verelli, NRC, R. Baker, GPC, A. Udy, EG&G Idaho, Inc.,

June 11, 1980, June 13, 1980, June 23, 1980, and June 25. 1980.

6. GPC letter, W. A. Widner, to U.S. Nuclear Regulatory Commission,

" Response to Request for Additional Information--System Voltage Study," dated October 9, 1980.

7. Telecons, R. Baker, GPC, A. Udy, EG&G Idaho, Inc., December 17 and 23, 1960, January 7 and 26, 1981, and February 13, 1981.

8. GPC letter, J. T. Beckham, to Division of Licensing, NRC, " Adequacy of Station Electric Distribution System Voltages, Response to Request for Additional Information," January 12, 1982.

e h

i 7

. -- - _