ML19247B608
| ML19247B608 | |
| Person / Time | |
|---|---|
| Site: | North Anna  |
| Issue date: | 08/07/1979 |
| From: | Brown S VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.) |
| To: | James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| Shared Package | |
| ML19247B609 | List: |
| References | |
| 403A, NUDOCS 7908100407 | |
| Download: ML19247B608 (16) | |
Text
t Vepco VlftGINl A ELECTRIC AND Pon ER COMP ANY, RICHMOND, VIRGINI A 23261 August 7,1979 Ser ial No. 403A Mr. James P. O'Reill y, Director PSE&C/WLT:mac: wang Office of Inspection & Enforcement U. S. Nuclear Regulatory Cormiission Docket No. 50-339 Region II 101 Marietta Street, Suite 3100 Atlanta, Georgia 30303
Dear Mr. O' Re ill y:
On April 27, 1979, a report was made under the provisions of 10CFR50.55(e) concerning potential overloads of electrical systens which supDly offsite power. This report was followed by our interim report dated May 23, 1979.
The work described is very near completion at this time and we are horeby submitting our final recort of this situation.
Our letter dated M3y 23,1979 stated that the loading through the fron offsite, under the conditions defined, cause components which carry oower Also we mentioned no deg*adation of equipment life for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> of ooeration.
the f act that automatic shedding of certain non-essential normal loads would be required undar the postulated conditions to achieve acceptable voltage levels and to mininiz? available f ault currents.
The worst case reserve systen loading that was considered in the design of the modification was one (1) unit in the start-up mode on -eserve power and the other unit at 100% cower en station se-vice pcwer then tripping and the resul tant transfer to the reserve power system. This represents the most conservative condition to consider in evaluating the reserve system loading r eq ui r emen ts.
Using the above condition as the olant coeratina requirement we then used The Emerqency the fol1owirg Emergency Bus eeauirements is a desicn basis.
Buses should not be inaavertently transferred from tne preferred source RSSTi to the s tandby source (Emergency DieselsT cn a transfer of the running unit to the reserve transform'es. Therefore, the voltace on the emergency buses mus t remain above 40% indefinitely or it must recover to greater th an 907, in 60 seconds or in the case of a safety injection, within 10 seconds.
Certain pre-conditiens will be required to assuro tn at tne worst-case in the voltage studies is not exceeded. Ti'ese conditions also loading used assure that one f eedwater puno and one ccndensate como will De running in eacn unit after automatic load sheddina has occurred. These conditions 3re as f o! l cws:
1.
A1y time a unit is in a start-uo moda wnen the other unit i s :n tn e line. a selector switch cn tne tr 3nsf ccmer cratection cinels fcr the s tart-uD unit mus t ce Dl 3ced in the "St 3r t-Uo" 3 S i ti 3n.
[
tuosiooyof 6 ' /
t Mr. Jazes P. O'Reilly, Director 2
?.
The unit that is on the line will be using two of thr*e stean generator feed pumps: the start-up unit will use only one feedwater pump (this complies wi th the sys tem design).
It will be required that the start-up unit usa the feedwate* pump with a letter designation (which indicates tne hus that it is fed ' rom) wn ich is different from the two operating on the other unit.
For example, if the unit on the line has its " A" and "C"
feedwater cumps operating, the start-up unit must use its "B" feedwater pump.
3.
The start-up unit must use the condensate pump which is fed from the same bus as its running feemfater pumo.
For instanca, if "3" feedwater pump is used for start-up, the "B" condensate pump must also be used.
4 The unit that is on the line may be running all tnree condensate pumps or mus t be running the two candensate pumps that are fed from the same buses that are feeding the two runnino feedwater pumps.
With tnese pre-conditions in ef fect, automatic load shedding will occur u pon the t"i o 77 th e un i t r,n t9 e l in 9 isi su$s equent f!s t tr ans f a-o f th e loads from the noesti s tatio9 service to the eserva s tation se*vice.
Ti1 4s load shed1ina will tria of f all high and 1 74 oressura neater drain pumps, two of three condensate Dumps, and one of twn feecwater pumps in the un i t th.s t w as tr ans f er ed to th e r es erv a s c ue ce.
Other 'iata ind assumptions that have been 'Ised in this study a*? as follows:
4 Minimun voltige on 500ky bus is 506ky based on studies n i c5 h av e previousl y been tr ansmittec.
3.
The eserve tr ansformer load tap changer will cor-ect voltagas to tha maximum axtent possible.
For moto s tPrting cc1ditions f accident cases) tha LTC position 5efore tha incident was datermined 5 ?s?d en raasar abl y axpectad pro-cc"1di tions, then was issumed to ra'ain in th is pos i tion wh i l e th e emer oen cy mo to r s ar e s tar te d.
C.
Safety infaction actuation
?sults in triop ng of all feedwater pumos i
on th a t un i t.
D.
'to o Dec ator action to educe load is 35%uned to ^ccur fer I hour a # tar a soi t trio.
F.
Dear 3ced vol tarn reliy crotection en tna i MO val' wn g?ncy bus es S es u rn c7nsider u and e il' act s ' ovate t h o e "e c y asei fr N
'ne Ur ifarr ed tourC? fr t*" Co9di ticns 2ndI)?ed O
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.e,
Mr. James P. O'Reilly, nirector 3
The enclosed data shows the results of our studies. This data clearly illustrates that for the worst esse conditions ersmined, as defined earlier, the system will have acceptible voltage levals, both for emargency motor starting and continuous operation of all equipnent. Following is a brief description of all enclosures:
Enclosura A: Three grao5fc results of studies conducted to examine tha worst case loading configu-ations which can occur for the two unit station under the non-accident conditions defined earlier. The loads indicated are those wnich will remain af ter losd shedding. The three dif ferant conditions represent the variations in loading tnat will occur dependent upon which feedwater pump the start-up unit uses. These results indicate that the voltagas available on the 4160 volt and 190 volt emergency buses are adequate to operate all the inads continuously.
Enclosura 3:
Two griphic results of studies conducted to exanine the two wa-st case loading configurations whicn could occur for centainment ia or es s u-i t ati on ictuation accicent conditions.
These cases are for accident ccnditions on ene unit wit 5 subsequrnt fast tr3nsfar of 19415, while the other unit is in its staat-up mode, and for 1ccidant conditions f er a un i t wh ile in s t a-t -u p wi th the o th e-unit trioped it 100% 994er vish subsequent fast transfer of loads. These resul ts show th at adequite i l -equ irn 1 l
voltiges a-a svallable to start and continuously con
?nergency leads.
It should 5e noted that the larga amar gan cy motors reach full soeed within four seconds, by which time the voltaq? will hiva recovered to acove 90% of the bus voltage rating.
Enclosure C-The enclosed ene-lina diagrams sh?v the -ev' sad electrical cowar dis tribution sys tem.
Enclosur? 0: T le enclosed logic di sgr sms shev the annunci3tien and contrai scquance for the lead sheddinq sche e. the -aserva station service lead meniter MS, and tre "evisad col 3yinq necess itated 5a tna *cy % Mns to tt.e f i*. tr 'nu t i en s ys te-1 Enclosure E: The enclosed letter frc, General Electric Cocpan y to our "r.
.lonn M. Dav is da ted, lune 3,1979 cocuments tha t our raserve s tation service transformer can carry 156% of maxiFum naneolate rating for cna 5 cur without siqnificant loss of life.
'Je ara continuing with other studies to furtne* upge nde tha offsite nower supplias to anit auxiliarv loads suc) tnat load snaddirq in d a.inin is tra t ive c-" t" O s af ?anitran t us 3ca will not he ** quired.
Tas, stutiss inclue cans + 1arit ion of tne iddi t on of Uni ts 3 an 1 4 a t t9 is s i ta.
i
(
Mr. James P. O'Reilly, Director 4
We consider this transmittal to fully define the capabilities of our reserve station service system as it apolies to the two unit station. We feel that this system meets all requirments of off site powar capability imposed by General Design Criterion 17, as wall as criteria of good general desien practice.
If you nead any further information, please contact this office.
v gy/truly,-vours,/
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i i Senior Vice! President - Power Station Eng19eering and Construction cc: Mr. Victor Stello, Director Office of Inspection ? Enforcement 4r. Harold R. Denton, Diractor Office of Nuclear Reactor Regulation G58337
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J bbb ELECTRIC UTILITY SALES DIVISION GENERAL ELECTRIC COMPANY, P.
O.
BOX 6974, RICHMOND, VIRGINIA 23230 Phone (804) 28S-4071 June 8, 1979
Subject:
Vepco P.O.
049766 G.E.
Regn. 326-88100 Reserve Station Service Transformers - North Anna Power Plant Mr. Jchn M. Davis Virginia Electric & Power Company Post Office Box 26666 Richmond, VA 23261
Dear Mr. Davis:
Our Medidm Transformer factory in Rome, Georgia, has analyzed the above referenced transformers to determine the overload capability of the windings and ancillary components.
Specifically, we assumed the transformer had been operating at 75% of maximum rated load for 8 - 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> prior to overload, in a 40 C ambient.
We then assumed an emergency occurred and the transformer was loaded to 177% of its maximum nameplate rating for one hour.
Under this condition, the top oil reached a temperature of g
110.5 C, and the winding hot spot temperature was 139.6 C.
The copper lead from the winding to the bushing reached a temper-ature of 209.8 C.
Based on these temperatures, our computer program predicts a.03%
loss of life for the winding and a 10% loss of life for the lead.
If the overload were limited to 156% of maximum nameplate rating 0
for one hour (52.4 MVA), the top oil temperature would reach 100.8 C, the winding hot spot would be 126.2 C, and the lead from the winding to bushing would reach 180 C.
These reduced temperatures would cause an insignificant loss of life for the winding and ancillary components.
0E!48
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GENER AL h ELECTRIC Mr. John M. Davis Page 2 June 8, 1979 Please let me know if further information is needed.
Sincerel,
Edmund N.
Summers Transmission Equipment Sales Engineer
/ljl cc:
JC Shaw MTPD, T.ome 9
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