ML20003C101

Adequacy of Station Electric Distribution Sys Voltages, Crystal River Unit 3, Preliminary Rept

ML20003C101
Person / Time
Site:	Crystal River
Issue date:	01/31/1981
From:	Udy A EG&G IDAHO, INC., EG&G, INC.
To:	Shemanski P Office of Nuclear Reactor Regulation
References
CON-FIN-A-6256 EGG-EA-5338, NUDOCS 8102260625
Download: ML20003C101 (13)

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. This is an informal report intended for use as a preliminary or working document Prepared for the U.S. Nuclear Regulatory Conunission Under DOE Contract No. DE-AC07-761D01570 g $ $ g $ Idaho FIN No. A6256 81022600M

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FORM EG&G N3 (Re. It 79)

INTERIM REPORT

, Accession No.

Report No. EGG-EA-5338 Contract Program or Project

Title:

Electricai, Instrumentation and Control System Support Subject of this Document:

Adequacy of Station Electric Distribut Ln System Voltages, Crystal River Unit 3, Docket No. 50-302, TAC No. 12743 Type of Document:

Informal Report Author (s): @$@@{@ gg "g

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Assistance Report Date of Document:

' January 1981 Responsible NRC Individual and NRC Office or Division:

Paul C. Shemanski, Division of Licensing This document was prepared primarily for preliminary or internat 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 I Prepared for the

' U.S. Nuclear Regulatory Commission Washington, D.C.

Under COE Contract No. DE-AC07 76lD01570 NRC FIN No. A6256 INTERIM REPORT.

0032J ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES CRYSTAL RIVER UNIT 3 Docket No. 50-302 January 1981 A. C. Udy Reliability and Statistics Branch Engineering Analysis Division EG&G Idaho, Inc.

Draft 1-15-81 TAC No. 12743

ABSTRACT The Nuclear Regulatory Commission has required all licensees to analyze the electric power system at each nuclear station. This review is to deter-mine if the onsite distribution system in conjunction with the offsite power sources has sufficient capacity and capability to automatically start and operate all required safety loads within the equipment voltage ratings.

This Technical Evaluttion Report reviews the submittals for Crystal River Unit 3.

The offsite power sources, in conjunction with the onsite distribution system, have been shown to have sufficient capacity and capability to auto-matically start as well as continuo. sly operate, all required safety related Icads within the equipment ratad vo tage limits in the event of either an .

anticipated transient or an accident condition.

FOREWORD Tnis report is supplied as part of the selected Electrica', Instrumen-t tation, and Control Systems (EICS) issues program being conducted for the U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation, Division of Operating Reactors, by EGSG Idaho, Inc., Reliability and Statis-tics Branch.

The U . Nuclear Regulatory Commission funded the work under the auth-orization entitled " Electrical, Instrumentation, and Control System Sup-port ," . B&R 20 19 01 03, FIN No. A6256.

CONTE NTS

1.0 INTRODUCTION

......................................... ............ 1

, 2.0 D ES IG N B AS I S C R I T E RI A . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 3.0 SYSTEM DESCRIPTION ................................................ 2 4.0 ANALYSIS DESCRIPTION .............................................. 4 4.1 Design / Operation Changes ..................................... 4 4.2 Analysis Conditions .......................................... 4 4.3 Analysis Results ............................................. 5 4.4 Analysis Verification ........................................ 5 5.0 EVALUATION ........................................................ 6

6.0 CONCLUSION

S ....................................................... 7

7.0 REFERENCES

........................................................ 8 FIGURE

1. Crystal River Unit 3 one-line diagram ............................. 3 TABLE

1. Class 1E Equipment Voltage Ratings and Analyzed Worst Case Load Terminal Voltages . . . . . . . . . . . . . .......... 5 111

. - . . - ~ . .. . . .- - -- ,. .. .. =

ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES

. CRYSTAL RIVER UNIT 3 f

1.0 INTRODUCTION

j: As 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

- of August 8, 1979,." Adequacy of Station Elettric Distribution Systems Volt-

- ages," required each licensee to confirm, by analysis, the adequacy of the voltage at the class 1E loads. This letter included 13 specific guide-

-lines ~ to be followed in determining if the load terminal voltage is adequate

- to start and continuously operate the class 1E loads.

~

1 Florida Power Corporation (FPC) responded to the NRC letter with a letter of April.3, 1980. .The Final Safety Analysis Report and the FPC response ' to questions regarding Reference 2, dated December 22, 1980,3 were also -reviewed for this report. A telephone call on January 5, 1981,0 > clarified portions of the Reference 3 response.

' Based on the information= supplied by~FPC, this report addresses the capacity and capability of the onsite distribution system of Crystal River

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Unit 3, in conjunction with the offsite power system, to maintain the volt-age for the required class 1E equipment within acceptable limits for the worst'-case starting and load conditions.

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2.0- DESIGN BASIS CRLIERIA-i~ . .

The positions applied in determining-the acceptability of the offsite l-voltage. conditions in supplying power to the class 1E equipment are derived-

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from the following:

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-1. General Design Criterion'17 (GDC 17), " Electrical Power Systems,"~of Appendix A, " General Design Criteria for Nuclear Power-Plants," of 10 CFR 50.

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2. General Design criteriot. 5 (GDC 5), " Sharing of struc-

-tures, Systems, and Components," of Appendix A, " General t

Design Criteria for Nuclear Power Plants," of 10 CFR 50. >

3. ' General Design Criterion 13 (GDC 13), " Instrumentation and Control," of Appendix A, " General Design Criteria 1

, for Nuclear Power Plants," of 10 CFR 50. -

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

5.. Staff positions as detailed in a letter sent to the licensee, dated August 8, 1979.1

6. ANSI C84.1-1977, " Voltage Ratings for Electric Power Systems and Equipment (60 Hz)."

Six ' review positions have been established from the NRC analysis guide-

' 1

, lines ;and the above-listed documents. These positions are stated in Section 5.0.

i 3.0 SYSTEM DESCRIPIION- '

' Figure l_is a simplified sketch of t'eh Crystal River Unit 3 (CR3)

.one-line diagram taken from Ammendment 42 PSAR Figures 8-8 and 8-9.

Units l'and 2'areinot nuclear' units'.

-CR3 hasitaree offsite' supplies to the class lE distribution system.

Tney are: ,

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.l." " Start up_ transformer.3 (SUr 3), connected to'the 230kV i switchyard.

2. _The unit ~ auxiliary transformer-(UAT), connected to the l

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unit _ generator by disconnect _ links and the 500kV switch-

-yard;(via a step-up_ transformer). 'The removal of the

'_  : generator-disconnect links allows'use of'the trans-

. .former asian offsite' source.

p 3.- -Startup transformer? l/2.(SUT:l/2), connected: to. th'e

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'230kV switchyard and associated with fossil-fueled EUnits 1-and 2.. -

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i TO 500 KV DISCONNECT o 230 KV s SWITCHYARD LINKS SWITCHYARD o / VIA STEP-UP

g. TRANSFORMER ^

UAT #3 SUT 83 WT TT mm mm

" DISCONNECT "

o LINKS o 3B 3A 6900V 6900V l

3B TCHYARD-3A 4160V ^ 4160V DG WW UNIT 1/2 DG 3B SVT g S3. _;, BUSES IB & 2B d 3A i

> BUSES 1A & 2A l 3B 3A 4160V 4160V NC CLASS lE N ' CLASS lE i

3B 3A 480V 480V CLASS lE CLASS lE CRYSTAL RIVER- d THESE 4160V BUSES ARE IN UNIT 3 FOSSIL FUELED UNITS 1 AND 2.

ONE LINE DIAGRAM 2. UNITS 1 AND 2 OUTPUT FIGURE 1 _ CONNECTED TO 230 KV

, SWITCHYARD.

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The 480V class lE ouses 3A and 3B are powerei by 4160V class IE buses 3A and 3B, respectively, by individual transformers. Technical Specification 3.8.2.1 prevents the use of the inter-tie between 480V ,

buses 3A and 3B during nuclear operation. '30V class IE motor-control centers (MCCs) use individual control trans rs to power the associated -

control circuits.

Essential 120V AC power is supplied by non-interruptable power sources that are backed-up by station batteries. Should an inverter be shut down for maintenance, self-regulating transformers (over a +15% input range) are uned.

4.0 ANALYSIS DESCRIPTION 4.1 Design / Operation Changes. The voltages shown on Table 1 are based on the licensee changing the tan etting of the Unit 3 SUT to the 230,000V tap.3 .

4.2 Analysis Conditions. FPC has determined by contingency plan-ning that the maximum expected 230kV offsite grid voltage is 243.6kV and the minimum is 236.4kV. Similarly, the maximum expected 500kV offsite grid voltage is 540kV and the minimum is 475kV.

FPC has analyzed each offsite source to the onsite distribution nystem under extremes of load and offsite voltage conditions to determine the voltages for the class lE equipment. The vorst case class lE equipment voltages occur under the following conditions:

1. The maximum steady-state load terminal voltage occurs using the Unit 3 SUT with the unit refueling load.

2. The minimum steady-state load terminal voltage occurs with the UAT supplying the unit refueling load. -

3. The minimum transient load terminal-voltage occurs with .

the conditions of 2 above concurrent with the start of the largest class IE motor.

4

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 4000V Motors Start -- --

85 --

90.6a Operate 110 109.2 90 92.9a __

460V Motors Start -- --

85 --

88.6a Operate 110 107.7 90 91.02 --

480V Starters Pickup -- --

80.5 87.2 84.9 Dropout -- --

55 87.2 84.9 Operate 110 103.2 85 87.2 --

Other Equipment C

a. Bus voltage; feeder cable drop negligible.2

. b. 80.5 is the average value when the coil is hot, 75 is the rated value when the coil is cold.5

c. Vital instrumentation and control loads are powered by non-interruptable power sources. The inverter automatically transfers ta the DC battery source if the AC voltage is outside of +10% of nominal. These loads are powered, during inverter maintenance, by self-regulating transfor-mers (+1% regulation over +15% input). ,

4.3 Analysis Result. Table 1 shows the projected worst case class lE equipment terminal voltages.

4.4 Analysis Verification. FPC has proposed to record bus voltages on ene plant auxiliary and class lE buses while Crystal River Unit 3 is operating and the 230kV grid voltage is held at 243.6kV. This test proced-ure would be repeated while the grid voltage is held at 236.4kV.

• These recorded voltages would be compared to calculated voltages.

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5.0 EVALUATION Six review positions have been established from the NRC analysis guide- ,

' I lines and the documents listed in Section 2.0 of this report. Each review position is stated below followed by an evaluation of the licensee submittals. The evaluations are based on completion of the design change described in Section 4.1.

. 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 IE equipment within the equipment voltage ratings.

FPC has shown,' by analysis, that Crystal River Unit 3 has sufficient capability.and: capacity for starting and continuously operating the class IE loads.within the-equipment voltage ratings (Table 1).

Position 2--With the maximum expected of fsite grid voltage and minimum ,

" load condition, each offsite source and' distribution-system connection combination must be' capable of ' continuously operating the required class IE

. equipment without exceedin'g the equipment voltage ratings.

FPC has shown,fby analysis, that the voltage ratings of the class 1E equipment will not be exceeded.

Position 3--Loss'of'offsite power to either of the redundant class IE distribution' systems due to operation of voltage protection relays, must

.not _ occur when the. offsite power source -is within expected voltage limits.

>EG&G: Idaho,-Inc.,.will verify, in;a separate report, that the require-

- ments.:of this position are satisfied (TAC No.- 10017).

Position 4--The LNRC!1etter requires that test-results verify:the ..

, accuracy.of:the voltage analyses supplied.

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FPC has proposed a test to verify the accuracy of the submitted analysis. This proposed cest is acceptable if the test values can be shown to accurately show feeder and transformer voltage drops. Further, this test should verify that the feeder cable voltage drops are negligible as assumed (see footnote a of Table 1).

Position 5--No event or condition should result in the simultanecus or consequential los, of both required circuits from the offsite power network to the onsite distribution system (GDC 17).

FPC has analyzed the connections of Crystal River Unit 3 to the offsite power grid, and has determined that no potential exists for simultaneous or consequential loss of more than one circuit from the of fsite 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 starting and operating voltage for all required class IE loads with an accident in one unit and an orderly shutdown and cooldown in the remaining units.

Crystal River is the site of one nuclear unit and two operating fossil-fueled units. With no interconnected nuclear units, position 6 is not applicable to Crystal River Unit 3.

6.0 CONCLUSION

S The voltage analyses submitted by FPC for Crystal River Unit 3 were evaluated in Section 5.0 of this report. Upon the completion of change described in Section 4.1, it was found that:

1. Voltages within the operating limits of the class lE equipment are supplied for all projected combinations of plant load and offsite power grid conditions. How -

ever, FPC should verify, by tect, that the feeder cable voltage drops are negligible.

2. The proposed test to verify the accuracy of the analysis is satisfactory if the test measurements are made with the class lE buses and MCCs loaded to at least 30% of their full load. If this is not possible, FPC shculd h

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define on what other basis their voltage measurements  ;

accurately acc>unt for feeder and transformer voltage j drops.  ;

3. FPC has determined that no potential for either a simultanous or a consequential loss of of fsite power l sources exists. -

EG&G Idaho, Inc., is performing a separate review of the undervoltage l relay protection at. Crystal River Unit 3. This will 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 Voltaga," August 8, 1979.

2. FPC letter, R. M. Bright, to-W. Gammill, U.S. NRC, " Adequacy of Station ,

Electric Distribution Systems Voltages," April 3, 1980.

3. FPC-letter, P. Y. Baynard, to R. W. Reid, U.S. NRC, " Adequacy of Sta-

l -tion Electric Distribution Systems Voltages," December 22, 1980.

4. . Telecon, A. C..Udy, EG&G Idaho, Inc., and K. Baker, FPC, January 5,

-1981.

15. Allen-Bradley letter, Van Smith'& Co., Tampa District Office, to FPC, Att: Gary Castleberry, " Crystal River Unit #3," December 3,1980.

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