ML17249A179

Responds to 790808 Ltr Re Adequacy of Station Electric Distribution Sys Voltages.Submits Sys Model & Acceptance Criteria for Use W/Proprietary Code PTI-PSS/E to Verify Offsite Power Capability.Final Rept Submitted in 60 Days

ML17249A179
Person / Time
Site:	Ginna, Sterling
Issue date:	10/08/1979
From:	Saddock H ROCHESTER GAS & ELECTRIC CORP.
To:	Ziemann D Office of Nuclear Reactor Regulation
References
TASK-08-01.A, TASK-RR NUDOCS 7910120205
Download: ML17249A179 (13)

Text

REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR: 7910120205 C. DATE: 79/10/08 NOTARIZ NO DOCKET 0 FACIL: 50-244 Robert Emmet Gonna Nuclear Plant> Unit 1> Rochester G 05000244 STN-50-485 Sterling Power Prospect Nuclear> Unit 1> Rochester 05000485 AUTH. NAME AUTHOR AFFILIATION SADDOCK> H. G. Rochester Gas 8c Electric Corp.

RECIP. NAME RECIPIENT AFFILIATION ZIEMANN> D. L. Operating Reactors Branch 2

SUBJECT:

Responds to 790808 ltr re adequacy of station c lee tric distribution sos voltages. Submits sos model / acceptance Criteria for use w/proprietqrg code PTi-PSS/E to verify offsite power capability. Final rept submitted in 60 days.

DISTRIBUTION CODE: A015S COPIES RECEIVED: LTR Q ENCL + SIZE:

NOTES: '.TITLE: Onsite Emergency Power Systems

-2 WS 8

//8PHKF EC I R'I ENT C..

rnif Tz COPIES

/YaF~8 ~

RECIPIENT S'7"4A/2) 8RS g 2-E'4R A/7 COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL ACTION: 05 BC 488 N 4 LA/

> 7 7 LA 4~~~<>

Laud A>

1, 0 INTERNAL: 0 EG FILE 1 1 02. NRC PDR 1 12 f47 DO 1 1 13 I8(E 2 2 15 OELD 1 1 16 MPA 1 1 17 AUXIL SYS BR 1 1 18 INC SYS BR 1 1 20 ENGR BR 1 1 21 REAC SFTY BR 1 1 22 PLANT SYS BR 1 23 ADV REAC BR 1 24 PWR SYS BR 1 1 25 WAMBACH T 1 26 TONDI D > 1 1 27 MCDONALD> D 1 1 28 HANNON> J 1 1 2'P BRINKMAN 1 1 30 EEB 8 HANAUER 1 1 EXTERNAL: 03 LPDR 1 1 04 NSIC 1 1 31 ACR S 16 16 Q~(~ J "( !

TOTAL NUMBER QF COPIES REQUIRED: LTTR ~

SV ENCL 58

/>Is]

I M EE' h I (E I'

El ( 'll) KM>>

I K

,"~

II

~ E Ig I E ') Q ME M." fff 'f'~

'f fi' 8f-P~

)) fh, I l,d gg J

Il 't

~K ~ M " S "p<."

ul Q I(

.3 (ll'-. (.")f , g)).M I>>u(/ II( E v

~ M l()4 t ~ IK ( ') ~ I

~ ~

.) 0'/j ) I, g V E.(d>>l )M(I)," f 'g ".

VI "f't>> Itu(1 f '

f(IE f "I 'It E

Y M E I gguh(

l 'AM%."-.ffif,.( "H ."gi'I . f (E

V>>"."

'] )1 "4 ',

K'hh,j(

(D

~

) M>>'l( '3 I

I Kfd'l M>> P Eg-, dh )P,(( 9 l E(

E(E 'll 'I ~ >>  ; 1 "] '

f f"..." %8."I'0", J sp

('i ~VAAWOQgt'f I '(

I ] u

'(f '"6'H

'>>J/, ~>('3f 5- i

>>I',(d )<;3 f Y(-l, ME

(y crrro crooI,

/Sfllllll j llllllllll, ROCHESTER GAS AND ELECTRIC CORPORATION e 89 EAST AVENUE, ROCHESTER, N.Y. 14649 HARRY G. SADDOCK QCI.CPHONC VICC PRC8IOCNT ARCA COOC 7ld 546.2700 October 8, 1979 Director of Nuclear Regulation Attention: Mr. Dennis L. Ziemann, Chief Operating Reactors Branch 42 Division of Operating Reactors U.S. Nuclear Regulatory Commission Washington, DC 20555

Subject:

Adeguacy of Station Electric Distribution Systems Voltages

Dear Mr. Ziemann:

In accordance with the letter, dated August 8, 1979 from William Gammill to All Power Reactor Licensees regarding the above subject, RG&E has prepared a system model and acceptance criteria for use with the proprietary code PTI-PSS/E, to exhaus-tively verify offsite power capability in accordance with GDC17.

Based on Enclosure 2, Guidelines for Voltage Drop Calculations of the August, 8 letter, and using the model described in Enclosure 1 of this letter, RG&E is evaluating the in plant voltage effects of possible grid variations in combination with all possible plant: operating modes. Since the number of combinations represent-ing possible system transient states to be analyzed is approxi-mately 100, these analyses are still being performed. The final results of these analyses will be transmitted sixty days from the date of this letter.

Subseguent to the completion of the system transient, load flow analyses, the results will be compared with syst: em historical

. data and current test, results. A status report on this portion of the study will be transmitted to you ninety days from the date of this letter.

In analyses performed thus far, no violations or potential violations of GDC17 have been identified.

Very truly yours, Harry G. Saddock T9I 0120 coLOcS

Enclosure 1 The electrical distribution system at the R.E. Ginna Nuclear Plant is being reviewed to determine if the potential exists for events or conditions that would be in violation of General Design Criteria (GDC) 17. This review is being accomplished by perform-ing a computer analysis assessing the electric system's capa-bility to adequately supply all safety loads. Following the analysis, all events or conditions that could result in the loss of both offsite sources will be identified.

The analysis is based on an interactive computer load flow program that models the entire electrical distribution system representing all plant operating modes as well as all anticipated electrical transient conditions. The load flow solutions then provide the bus voltages and the power flows on each bus for the various cases studied. The results of this analysis, particularly the voltage levels on the safety buses, are then evaluated to deter-mine if a potential exists for low voltage transients that would cause spurious tripping from an offsite source. This would indicate that, the system itself lacks sufficient capacity to automatically start and operate all reguired safety loads for those operating modes where low or degraded voltages potentially exist. Finally, all results, conclusions, future modifications or changes to operating limits resulting from this report will be summarized.

Load Flow A~nal sls The electrical distribution system at Ginna Station is shown on Figure I, the single line diagram. The offsite sources are two 34.5 Kv'circuits, designated 767 and 751.

The immediately available source of offsite power is 767 circuit. which is tied to the RG&E 115 Kv grid, designated 13A. The 751 circuit is normally energized and available by means of a manual transfer from the main control room. When 767 circuit is out of service, 751 circuit is the immediately available offsite source. The grid is operated at 117 Kv to 122 Kv normally with the plant "on line" and 113 Kv to 122 Kv with the plant "off line".

The safeguards or IE distribution system is divided into two redundant and completely independent, trains, A and B. As described in the Ginna Station FSAR, each train is designed to mitigate the consequences of the worst case accident.

Train A and B are each made up of two safeguards 480 volt buses, train A consists of buses 14 and 18 while train B consists of buses 16 and 17. These safeguards buses are labled as IE on the single line diagram, Figure I.

1" h

i 1 I

Presently, each IE bus contains two independent undervoltage (loss of voltage) systems, 27 and 27B. Each undervoltage monitor is set at approximately 65% of nominal voltage. No spurious tripping has been indicated in analyses performed to date and none has been experienced over the past ten operating years.

The existing undervoltage system is being upgraded and the loss of voltage systems setpoint will be raised to 77%. In addition a second level, inverse time system will be installed on each bus with the setpoints shown on figure II. This figure shows the maximum proposed voltage and time values that will be part of the technical specifications. The maximum second level and the new loss of voltage setpoints are summarized below:

Undervoltage Undervoltage Relay

~Sstem ~set oint Max. Time dela set oint Loss of voltage 368 volts < 8.5 seconds Degraded voltage 414 volts < 1600 seconds Since the above values are maximum values, the actual relay settings will be determined by this analysis and the operating limits will be imposed on the new under-voltage system.

0 For additional details of the new loss of voltage and second level systems, refer to references 1 and 2.

Operating Modes:

All the "on-line", "off-line", load, offsite voltage levels and transient conditions are being evaluated in the load flow program. The operating modes and condi-tions are described below.

a) The Plant "on line" with IE normal bus loads and with the 115 kV grid as the offsite source which assumes minimum, nominal, and maximum voltage levels.

b) The Plant "on line" with heavy plant loading.

This reflects all safety loads in service with the grid as the offsite source which assumes minimum,,nominal, and maximum voltage levels.

c) The plant "on line" with normal loads and 751 circuit as the offsite sources.

d) The plant "on line" with heavy IE bus loads and 751 circuit as the offsite source.

\

t'>

e) Transient Conditions Motor starting either 4 Kv or 480 volt safety related motors.

Plant trip where the auxiliary plant loads are transferred onto one of the two offsite sources.

Start-up conditions.

f) "Off line" light and heavy loads representing cold shutdown conditions with the grid and/or the 34.5 Kv source at minimum, normal and maximum levels.

The acceptance criteria for determining compliance to GDC-17 are as follows:

Continuous safeguard voltage levels higher then 484 volts and lower than 414 volts must be reviewed for either reduction of equipment design life and/or degrada-tion in equipment capability to perform required safety functions, and for a potential spurious tripping of the offsite source.

The acceptance criteria for determining abnormal voltage levels are:

Any of the inplant bus voltages that have been calculated to be at or below the loss of voltage set point of 368 volts are abnormal and will violate GDC-17.

Any of the inplant bus voltages that have been calculated to be at or below the second level set point of 414 volts are abnormal and potentially violate GDC-17.

3. Any of the inplant bus voltages that have been calculated to be equal to or greater than the upper ten percent design limit of the 440 volts base motors or 484 volts are abnormal and potentially violate of GDC-17.

Bus voltages that are between 414 and 484 volts on the Safeguard buses are defined as normal and those operating modes or conditions do not in any way compromise the offsite source and therefore meet the intent of GDC-17.

Safeguards voltage levels that dip below 414 volts during a transient condition but nearer to a higher level must be reviewed for possible spurious tripping.

The degrade undervoltage trip point, will be set at 414 volts with a long time delay. The loss of voltage set point will be at 368 volts with an instantaneous trip at that level.