ML19263C887
| ML19263C887 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley, Trojan |
| Issue date: | 03/07/1979 |
| From: | Dunn C DUQUESNE LIGHT CO. |
| To: | Schwencer A Office of Nuclear Reactor Regulation |
| References | |
| TAC-10007, NUDOCS 7903120299 | |
| Download: ML19263C887 (4) | |
Text
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"Qf Duquesne Udit im -
435 Sixth Avenue Pittsburgh, Pennsylvania 5219 March 7, 1979 Director of Nuclear Reactor Regulation United States Nuclear Regulatory Commission Attention:
A. Schwencer, Chief Operating Reactors Branch No. 1 Division of Operating Reactors Washington, D. C.
20555
Reference:
Beaver Valley Power Station, Unit No. 1 Docket No. 50-334 Response to January 18, 1979 Request for Information Centlemen:
In response to your request for additional information concerning voltages on the safety related station service electrical buses at the Beaver Valley Power Station, the following replies have been prepared by the Electrical Protection Section of the Duquesne Light Company Electrical Engineering Department.
(1) Our undervoltage relay setting of 80% of nominal bus voltage is based on our experience with other power stations on our systems as well as the transmission system as a whole.
To our knowledge, we have never encountered equipment failure caused by sustained undervoltage. We feel that if such a low sustained voltage should occur, it would have to be caused by a mismatch of generation and load which would make itself evident in the form of reduced quency.
Automatic measures are initiated to correct this situation as defined in the document we referred to in our letter of November 11, 1976.
It is our opinion that plant equipment will not be damaged for the short duration of undervoltage that may occur during this excursion.
We are presently attempting to obtain specific information from motor suppliers to substantiate our position. The information is not available at this time.
7903120 d.
Beaver Valley Power Station, Unit No. 1 Docket No. 50-334 Response to January 18, 1979 Request for Information Page --
(2) The calculated voltage on the safety related busses were submitted in our letter dated November 11, 1976.
(C. N. Dunn to Robert W. Reid.) This information did not include transients during automatic transfer; however, from computer studies made for the condition of automatic transfer from the main generator source to the offsite source, the initial voltage on the terminals of the 4160V emergency motors at the moment transfer was completed was 85% voltage and recovered to 94% voltage within 0.9 seconds.
(Note - the study length was 1.0 seconds.)
In item 1 of our letter, we stated that we are awaiting information
~from motor manufacturers to substantiate our position concerning under-voltage protection.
Since this information is not available at this time, we will plan to make the following modifications to the control scheme.
However, if during the process of making this modification we obtain substantive data, we will notify you and advise you of our plans.
(Please refer to the attached sketch.)
(1) We will add an additional undervoltage relay to each of the 4160V cecrgency busses lAE and 1DF, set for 90% voltage.
(2) These undervoltage relays will operate a timing relay set for 1.0 minute.
(3) The timing relay will cause the tripping of the emergency bus tie breaker.
Control circuits will block this trip so that the emergency bus can be manually.re-energized from offsite power if the diesel generator should fail.
The Duquesne Light Company Engineering Department is presently engaged in a large amount of engineering work associated with several major design
~
modifications.which are to be installed during the first refueling outage.
It will not be possible to begin the detailed engineering required to install the additional undervoltage relays until the latter part of this year.
The new undervoltage protection system will be installed and in service no later than December, 1980.
Very truly yours, C. N. Dunn Vice-President, Operations Attachment
TO TO SYSTEM STATION MAIN GENERATOR LEADS SERVICE TRANSFORMER STATION SERVICE TRANSFORMER (138kV)
(22kV4 N.O.
11A N.C.
11C
[
SYSTEM SHOWN IN NORMAL OPERATING 4160V !!ORMAL BUS 1A CONDITION.
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PRIM N
U.V.
- SEC.
f LOADS
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U.V.
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LOAD D-G START RELAY
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N.C.
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4160V DIERG.
l BUS lAE
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LOADS LAA AJJ W
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l-8N 1-8N1 N.C. y3-
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480V EM G.
480V D1 ERG.
BUS 3 N BUS INl GJ LJ l_
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LCADS LCADS U.V.
U.V.
NOTES N.C. - Normally Closed N.O. - Normally Open U.V. - Undervol tage Relay Dotted Lines indicate devices tripped by U.V.
relay.-
4160V Bus ID, IDF, D-Gen # 2, e tc BEAVER VALLEY P.S. - UNIT is similar to the above.
SIMPLIFIED DIAGRAM OF NORMA U ES & UNDER
- Setpoints for existing relays VOLTAGE PROTECTION are given in our letter of July 22, 1977.
PC #2321
'Rev. l'2[2'0/79 O
(CORPORATE SEAL)
Attest:
Yb H.W. Staas Secretary COMMONWEALTH OF PENNSYLVANIA)
) SS:
COUNTY OF ALLEGIENY
)
On this
"/
day of M
1979, before me, HENRY G. STOECKER a Notary Pu#blic in and for said Common-wealth and County, personally appeared C. N. Dunn, who being duly sworn, deposed, and said that (1) he is Vice President of Duquesne Light, (2) he is duly authorized to execute and file the foregoing Submittal on behalf of said Company, and (3) the statements set forth in the Submittal are true and correct to the best of his knowledge, information and belief.
1
+
ENRY G. STOECrER, Notary Pub!ic F1t:sburgh, Nieghery County, Pa.
My Ccmmasion Expites Feb:uary 20.1982