ML18082B289
| ML18082B289 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 10/10/1979 |
| From: | Librizzi F Public Service Enterprise Group |
| To: | Gammill W Office of Nuclear Reactor Regulation |
| Shared Package | |
| ML18082B279 | List: |
| References | |
| NUDOCS 8010060286 | |
| Download: ML18082B289 (4) | |
Text
PS~G ATTACHMENT 2 Public Service Electric and Gas Company October 10, 1979 Director of Nuclear Reactor Regulation u.s. Nuclear Requlatory Conunission Washington, DC 20555 J
Attention:
Mr. William Gammill, Acting Assistant Director for Operating Reactors Projects Division of Operating Reactors Gentlemen:
ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES -
SALEM GENERATING STATION UNITS NOS. 1 AND 2 We have performed the analysis on the Salem Generating Station Units Nos. 1 and 2 electric power system in accordance with NRC letter, Adequacy of Station Electric Distribution System Voltages dated August B, 1979 and its enclosures.
The analysis demonstrates that the off site power system and the onsite distribution system is of sufficient capacity and capa-bility to automatically start as well as operate all safety loads within their voltage ratings for all anticipated transients and accidents.
Satisfactory results were obtained as a result of the original design considerations.
The Salem Generating Station was desiqned such that the resulting voltage profile was within component voltage limitations, being +5% of transformer secondary voltage and -10% of motor nameplate voltage under steady-state conditions.
The system was also designed such that the inrush current associ-ated with the start of a 6000 horsepower, 4.0 kV motor would not cause the bus voltages to drop below 80%.
All motors are de-signed to accelerate their driven equipment with at least 80%
motor nameplate voltage applied to its terminals.
This was accomplished by optimum selection of transformer impedances, incorporation of no-load taps on all power and unit substation transformers, and a + 10% automatic load tap changer on all the 13.8/4.16 station poW"er transformers.
All motor starters have a guaranteed drop out voltage of 70%.
All starters were bought with 300 VA control power transformers, regardless of NEMA size, to minimize voltage drop at the contactor coil. Further, con-sideration was given to cable size and length to limit voltage drop in a feeder.
The Energy People 95-5330 (1QOM) 1-78
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Dir. df H~. ReaAr Revulation **
10-10-79
'lbe analysis showed t:he worse *uatained under-voltaqa condition
- imposed upon the distribution aystem occurred with a severely de-graded SOOkV offaite ayst~ aimultaneous with a concurrent LOCA on Unit 2 anc! Unit trip on Unit 1 (or vice veraa). Thie unc!ar-voltaqe condition result* from the automatic i:ranafer of the fJX'OUP buses from the auxiliary power uansf ormera i:O the etation power transformer an4 th* automatic start of the required vital
-bus.loads. l'or ~*condition the.lowest volta9eli.at t:he 4.16 kV,.460V and 230V loads were *917 1.923 and.91 per unit re-spectively. The.above.analysis indicates that t:he onaite dis-tribution system and its components will operate within component
- voltage limitations.* The motors are t:he limiting component under
.steady-state conditions as they are 4esigned.tO run continuoµsly.
at..9 per unit *nameplate voltage.
'l'ransient*voltage drops due to t:he &tarting of motors were analyzed at each voltage level with no adverse effects. This analysis assumed the prestart voltage to be that corresponding to the*
deqraded 500 kV system and 1:he load in parallel with the motor being started equal to t:be maximum continuous rating of the transformer to which it is c:onneote4 leas the running load.of the motor being started. Further, the impedance of the parallel l.Oad
- was conservatively assumed 'to decrease as the aquare of the bus voltage to analytically eompensate for the additional current drawn by induction motors *upon decrease *in voltage. 'l'he minillium transient voltages obtained on the 4.16 kV, 460V and 230V levels were.86,.86 and.78 per unit, respectively for a duration of
.approximately 5 99conda.
'l'heae transients are within motor and motor starter design capabilities, thereby having no adverse effect on system operation.
The result* of this analysis were used to reexamine under-voltage protective settings and establish that no spurious separations of the safety buses from off site power would occur..
The 5 kV power cables that oonnect the 13.8/4.16 *kv statiOn power transformers to t:he qroup and vital buses are the load.limiting component in the distribution system.
The sixteen hour rating of the cable is utilised for the load that results from the concur*
rent LOCA Unit 2 and Unit trip on Unit 1. There is sufficient margin between the cable ratin9 and the resultant load to allow for implementation of e~iating atation procedures used during the events analyzed and thus, avoid overloading.
As indicated in the NRC letter of August 8, 1979, teats had been previously run to correlate calculations with field conditions.
With Salem Units 1 and 2 and the 500 kV aystem in an existing mode corresponding to a CJiven loading of.the plant distribution system, selected system parameters were monitored over a 24-hour period.
An analysis was then performed using.the actual load and 500 kV system volta9e to obtain a calculated voltage profile and compare to actual measurementa.
The calculations and field measurements correlated within very reasonable aoouraoy, thus
r Dir. of Nuc. Reactor Regulation *10-10-79 substantiatinq our assumptions and the method of calculation.
The results are qiven in Attachment 1. Further, a test on a cold 6000 horsepower, 4.0 kV reactor coolant pwnp motor was conducted.
The bus voltaqe dropped 15t upon start of this motor.
No adverse effects were observed on other operatinq equipment.
The results of this test substantiate the oriqinal plant design baaia.
'1'he electric power system was reviewed to determine if there are any events or conditions which could result in the* simultaneous or consequential loss of required circuits to the of fsite network that would violate GDC-17.
No potential exists for violation of GDC-17.
If you should have any questions, please do not heaitate to contact us.
Very* truly youra,..
t:P )/ ~
Frank P. ~~
General Manager -
Electric Production
500 kV Bus 13 kV Bus No. 11 Sta. Pwr.
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SALEM GENERATING STATION, UNIT 2 VOLTAGE PROFILE FIELD MEASUREMENTS VS. CALCULATIONS No. 21 U J Sta. Pwr.
I 4200 Measured i
L---4_1_s_6_ca_~cula ted j Lumped 4 kV Running Lead 19.27 MVA 4 kV BUS 4160/480V 465-470 Measured 470 Calculated 460V BUS Lumpe 460V Load Running 580 KVA To Response to NRC Letter 1deguacy of Station Electric Distribution 35-239 MeasureCS 239.l calculat~
System Voltage - Dated August 8, 1979 160/240
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