ML17318A323
| ML17318A323 | |
| Person / Time | |
|---|---|
| Site: | Cook  |
| Issue date: | 10/05/1979 |
| From: | Hunter R INDIANA MICHIGAN POWER CO. |
| To: | Harold Denton Office of Nuclear Reactor Regulation |
| References | |
| AEP:NRC:00270, AEP:NRC:270, NUDOCS 7910100181 | |
| Download: ML17318A323 (8) | |
Text
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SUBJECT:
Submits info re undervoltage protection sysrin response to NRC ltr from A Schwencer.
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TITLE: Onsi te Emer gency Power Systems ES.
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ACCESSION NBR:7910100181, DOC.DATE: 79/10/05 NOTARIZED!
NO DOCKET FACIL:50-315 Donald C.
Cook Nuclear Power Pl anti Unit ii Indiana 8
05000315 50-316 Donald CD Cook Nuclear Power Plantg Unit 2r Indiana L
05000316 AUTH,NAME AUTHOR AFFILIATION HUNTER~R,S.
Indiana L Michigan Power Co, RECIP ~ NAME'ECIPIENT AFFILIATION DENTONeHeR ~
Office of Nuclear Reactor Regulation INTERNAL: 01 12 TA/EDO 15 OELD 17 AUXIL SYS BR 20 ENGR BR 22 PLANT SYS BR 2A PNR, SYS BR 26 TONDIzD 28 HANNONrJ 30 EEB EXTERNAL: 03 LPDR 31 ACRS 1
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02 NRC PDR 13 ILE 16 MPA 18 ILC 8YS BR 21 REAC SFTY BR 23 ADV REAC BR 25 NAMBACH T 27 MCDONALDeD 29 BRINKMAN S
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4 INDIANA 5 MICHIGAN POWER COMPANY P. O. BOX 18 B0WLING CAREEN sTATIOH NEW YORK, hl. Y. 10004 October 5, 1979 AEP:NRC:00270 Donald C.
Cook Nuclear Plant Unit Nos.
1 and 2
Docket Nos.
50-315 and 50-316-License Nos.
DPR-58 and DPR-74 Degraded Grid Voltage Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation U.S.Nuclear Regulatory Commission Washington, D.C.
20555
Dear Mr. Denton:
This letter is in response to Mr. A. Schwencer's letter concerning the undervoltage protection system at the Donald C.
Cook Nuclear Plant.
I, The second level of undervoltage monitors are installed in a manner which meets the functional requirements of IEEE 279-1971.
The monitors trip the 4 kV,circuit breakers which connect the safety buses to the non-safety buses only when the auxiliary system is supplied from the preferred offsite pow'er source.
At all other times,.the monitors provide only a'low voltage alarm function for the preferred offsite power source.
'he voltage monitors are connected to the power source they monitor, that".is, the, preferred offsite power source.
The connection is made at the '34.5 kV voltage, level to provide sufficient selectivity and sensi-tivity to lower than normal auxiliary bus vol,tages without the need for long time delays,. 'he voltage'etpoints-selected correspond to a
4 kV voltage level of 90/ of nominal under worst steady state loading conditions.
The 2 second time delay permits automatic corrective. action to occur for transients on the high voltage system which could cause
. momentary voltage reductions of the measured voltage.
The voltage level selected also permits large motor starting on the auxiliary bus, which
,represents a transient load, with its attendant voltage drop,'hile the motor accelerates to rated speed.
In the case of.the'largest
- motor, the time required to override this transient is approximately two minutes.
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Denton tober 5, 1979 P:NRC:00270 Two 34.5 kV circuits are provided from the 34.5 kV high voltage s&itchyard bus.
Each circuit provides power to one of the two reserve transformers in each unit.
Each of the transformers provides power for one of the two safety trains of each unit.
The 34.5 kV potential trans-formers which convert the high voltage to a lower voltage are located at the primary terminals of the reserve transformers.
Each set of potential transformers consists of 3 transformers.
The primary winding of each transformer is connected phase to phase with two primary fuses.
Four sets of potential transformers are provided, one set for each of the safety trains of each of the two units.
The potential transformers are subjected to the same environment as the reserve transformers to which they are connected.
The three undervoltage relays and time delay relay for each safety train of each unit are located in the unit control room in safety related control panels.
The trip logic requires undervoltage sensed by at least 2 of the 3 undervoltage relays for 2 seconds before initiation of the tnp of the safety bus when it is fed from the preferred offsite power source.
Undervoltage sensed by only one of the three relays operates an annunciator.
Failure of any high or low voltage fuse or potential trans-former in the voltage sensing circuit will result in operation of only one of the three relays which will not cause a spurious operation of the system.
The single failure will cause operation of an alarm and therefore will not be undetected.
The 34.5 kV potential transformers are dedicated to the 'second level trip and are not used by or shared with any unrelated non-safety system.
In addition to the above, undervoltage alarms have been installed on each of the 4 kV and 600 volt buses to alert the operator of a low voltage condition should it occur.
These annunciators are active at all times.
We believe that the presently installed second level undervoltage trip which separates the safety bus from the non-safety bus when power is supplied from the preferred offsite source meets the intent of the requirements of IEEE 279-1971 as they apply to actuator systems and there-fore meets the intent of Staff Position 1 (e) Relative to the Emergency Power Systems for Operating Reactors.
As the information contained herein supplements previously trans-mitted information and is being submitted in response to a written request by the
- NRC, AEP interprets 10 CFR 170 as requiring that no fee accompany this submittal.
Very truly yours,
. Hunter Vice President
~ s k
Mr. Harold R. Denton
, Director 0
October 5,
1979 AEP:NRC:00270 cc; R.C, Callen G. Charnoff 3.
E, Dolan".
R.
W. Jurgensen D. V. Shaller -Bridgman
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