ML19319B965
| ML19319B965 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 02/04/1977 |
| From: | Roe L TOLEDO EDISON CO. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 8001290698 | |
| Download: ML19319B965 (6) | |
Text
NRCFonM 195 U.S. NUCLE AR NEGULATORY
- MISSION DOCKET NUMXER
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50-346 12 m
'NRC D,lSTRIBUTION FoR PART 50 DOCKET MATERI AL FROM:
DATE oF DOCUMENT TO:
Toledo Edison Company' 2/4/77
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g, John F. -Stolz Toledo, Ohio
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Lowell E. Roe
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2/9/77 E ETTER O NoToRIZ E D PROP INPUT FORM NUMBER oF COPIES RECE4VED
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% NC LASSIFIE D OCopy One signed DESCf41PTioN ENCLOSURE
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DO NOT ^W~'yOVE.,
Ltr. re our 1/25/77 ltr. and their 11/3/76 ltr.... furnishing further information regardin ;
offsite power systems (degraded grid voltage conditions)...........
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Davis-Besse SAFETY FOR ACTION /INFORMATION FwTnn 2/10/77 RJL i ASSIG:":D AD:
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fyQHf.IT_M_Ad' Af;ER; L. Engle PROJECT MANAGER:
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INTERNAL DISTRIBUTION RE_
SYSTEMS SAFETY I
PLANT SYSTEMS
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Serial No. 209 Q/
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Docket No. 50-346 ru..,, -.,.. -
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um.a m..a n a, Director of Nuclear Reactor Regulations k
e Attn: Mr. John F. Stol::
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f, Chief Light Water Reactors
\\e Branch No. 1 Division of Project Management
_ A[j United States Nuclear Regulatory Commission N' / 7 i Washington, D. C.
20555
Dear Mr. Stolz:
Your letter to us dated January 25, 1977 requested further information regarding offsite power systems (degraded grid voltage conditions) at Davis-Besse Unit No.
1.
The supplemental questions (the enclosure to your 1-25-77 letter) numbered one through five are answered or scheduled to be answered as follows:
Ouestion 1.
Based on the grid system stability analysis results, state the nominal value and the maximum and minimum spread values of voltage and frequency of the offsite power source that assures satisfactory operability of all electrical equipment of the station during all modes of plant operation.
Response
This question was answered in our letter of 11-3-76, Serial No. 144, response to questions IB and ID.
Further clarification is offered below:
The offsite power source is a nominal 345 KV, 60 HZ system. The maximum and minimum spread values of voltages are defined by the following two modes of plant operations.
Mode Auxiliary Loads 345 KV System 345 KV System of Operation Supplied frem:
Voltage Maximum Voltage Minimum 1.
Unit auxiliary transformer 102.1%
101.7*.
with corresponding 25 KV bus voltage 9 8. 7 *.'
101.3%
\\N THE TOLE 00 EDISCN CCMPANY ECISON PLAZA 300 MACIGCN AVENUE TCLEDO. CHIO 43652 1.w.a
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Startup transformer 102.2%
98.3%
with Davis-Besse not operating The spread values of voltage are the permissible operating range of the grid system voltage at the Davis-Besse Unit No. I switchyard.
Since an increase in the grid system voltage would result in an increased stability limit, the minimum grid system voltage is the determining factor of the stability limit for the Davis-Besse Unit No. 1 in terms of voltage. The grid system stability analysis was performed for a 25 KV bus voltage of 95.6% as determined by the minimum operating voltage of the turbine generator. Therefore, the minimum permissible operating voltage of the grid, for mode operation number one (auxiliaries are supplied through the unit auxiliary transformer), is above the analyze grid system stability limit.
The grid system stability analysis was performed to evaluate the perfor-mance of the Davis-Besse Unit No. I while the turbine generator is synchronized with the grid system. Therefore, the analysis does not pertain to the grid system while operating under mode number two (auxil-iary supplied through the startup transformers).
The maximum and minimum spread values of frequency are determined by the operating conditions of the grid system. The grid system is operated under guidelines established by the East Central Area Reliability Agree-(ECAR) of which the Toledo Edison Company system is a member.
ment These guidelines include an ECAR document number three, (emergency procedures during declining system frequency.) Under this document a program cutlines specific procedures to be implemented during declining system frequency conditions. These procedures include utilizing, to the extent practicable, all operating and emergency reserves, localized non-automatic procedures automatic load shedding, further manual or automatic load shedding, coordinated network separation, and isolating of generating units. The purpose of these procedures is to maintain the frequency q
spread of 60.0 to 59.0 HZ.
For over f requency conditions, administrative j
controls are initiated to maintain the frequency to 60 HZ.
In order to assure satisfactory operability of all electrical equipment of the station during all modes of plant operations further analysis will be performed. This is to be submitted March 4, 1977.
Question and Response The response to question 2 is to be answered March 4.
i Question i
j 3.
Provide a description of the procedures used to maintain grid configuration and operation in a condition which always satisfies the limits identified in question 1.
Also, provide the following; base; on the grid system stability analyses results:
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4
1
Response
Transmission line outage time is kept to a minimum consistent with good operating practices. A line suddenly forced out of service is returned to service as fast as possible consistent with good operating practices.
Maintenance outages on major transmission lines in a geographical area are coordinated with neighboring systems to avoid simultaneous maintenance 4
outages of two or more major transmission facilities. Proper grid I
voltage and frequency is automatically regulated and maintained by all generating units on the interconnected system.
Question l
3A.
Describe how the operator is made aware of the operation of the i
grid in regard to the 1.imits identifisd in question 1.
Response
Alarms are available from the computer for high and low voltage conditions and high and low frequency conditions.
Setpoints have not yet been made. Visual Indications on CRT are available on voltage condition.
They are not available for frequency conditions.
In addition three methods of direct communication between the Davis-Besse Operators and the TECo System Load Dispatchers Office are available for the Davis-Besse operators use; they are microwave, radio, and commercial telephone.
These communication paths are used for the coordination and interchange of information.
Question l
3B.
The effects of loss of the nuclear generating unit on offsite power source while operating at the limits identified in question 1.
Response
The Toledo Edison system is connected by six 345 KV and five 138 KV circuits with the interconnected grid. This interconnected grid includes the U.S. electric systems from the East Coast to the Rocky Mountains excluding part of Texas. A portion of Canada and Mexico are also con-nected to this grid. The present connected generation capacity to this grid system is between 325,000 and 350,000 Megawatts. The nominal operating frequency of the entire network grid is 60 HZ.
A transient stability analysis is not an appropriate means to determine the frequency effect of the sudden loss of generation. However, operating experience will give the best indication of frequency variation with loss of genera-tion. During the past 20 years the maximum frequency of the grid observed by Toledo Edison operators is estimated to be no greater than 60.03 HZ.
The minimum frequency was observed to be 59.845 HZ on January 17, 1977 during a period of extreme cold weather and high generation unavailability throughout the entire interconnected grid. The sudden loss of the Davis-Besse #1 unit will cause the steady state frequency of the inter-connected grid to drop no lower than.04 HZ.
The steady state deviation indicated above occurs after a series of oscillations have damped out but prior to governor action of the units on the interconnected grid i
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f 's I
. d which act automatically to restore the grid frequency to previous level.
In future years as more generation is added to this grid the frequency deviation for the loss of the Davis-Besse #1 unit will become less.
Question 3C.
The effects of loss of the largest grid load on offsite power source while operating at the limits identified in question 1.
Response
The largest single grid load within the ECAR area is the 2,000 MW load at the Portsmouth, Ohio ERDA plant. The sudden loss of this entire load will cause the frequency of the entire interconnected grid to rise a maximum of.08 HZ from the operating level prior to the loss.
Question 3D.
Identify any restrictions placed on the grid operation that require specific spinning reserve (either real or reactive pcwer) to be available within a dedicated distance from the nuclear station in order to maintain the offsite power source within the limits identi-fled in question 1 during grid disturbances.
Response
Toledo Edison along with the 18 other member systems of tne East Central Area Reliability (ECAR) Coordination Council has determined that a regulation (spinning) reserve of 3% is adequate to provide for reliable grid operation. This requirement is contained in ECAR Docket #2 (daily operating reserve) and reads as follows:
"B.
Daily Operating Reserve Requirements Each ECAR system shall provide, as a minimum, daily operating reserves equal to the amounts set forth respectively in Subsec-tion 1. below.
1.
An amount equal to three percent of the maximum 60-minute integrated clock hour internal load predicted for the day to provide for load regulation and for system frequency regulation. This portion of the operating reserves shall be spinning reserve within the control area of the system."
Question and Response The response to question 4 is to be answered March 4.
Question and Response
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The response to question 5 is to be answered March 4
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W Further we wish to clarify the implementat. ion date of a commitment we made in letter 1-4-77 (Serial No.179). The subject undervoltage relays will be operable by commercial operation of Davis-Besse Unit 1.
Very truly yours, f/
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