ML18081A357
| ML18081A357 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 10/10/1979 |
| From: | Librizzi F Public Service Enterprise Group |
| To: | Gammill W Office of Nuclear Reactor Regulation |
| References | |
| NUDOCS 7910160462 | |
| Download: ML18081A357 (4) | |
Text
,
~*
PS~G Public Service Electric and Gas Company 80 Park Place Newark, N.J. 07101 Phone 201/430-7000 October 10, 1979 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, DC 20555 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. l 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 8, 1979 and its enclosures.
The analysis demonstrates that the offsite '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 anticip~ted transients and accidents.
Satisfactory results were obtained as a result of the original design considerations.
The Salem Generating Station was designed 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 accelera~e 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 power transformers.
All motor starters have a guaranteed drop out voltage of 70%.
All starters were bought with 300 VA control power transformers, regardless of NE.MA. size, to minimize ~oltage <lrop at the contactor coil.
Further, con-sideration was. given to cable size and length to limit voltage
~
d;~ a feeder.
f)ce\\\\f/ \\
ll\\\\llSOI'
'- I /
sEmm; 7 91016-0\\*~.(o ~
p 95-2001 (200M) 2-78
~* Dir. of Nuc. Reactor Regulation 10-10-79 The analysis showed the worse sustained under-voltage condition imposed upon the distribution system occurred with a severely de-graded 500kV offsite system simultaneous with a concurrent LOCA on Unit 2 and tJnit trip on Unit 1 (.or vice versa).
This under-voltage condition results from the automatic transfer of the group buses from the auxiliary power transformers to the station power transformer and the automatic start of the required vital bus loads.
For this condition the lowest voltages at the 4~16 kV, 460V and 230V loads were.917,.923 and.91. per unit re-spectively.
The above analysis indicates that the onsite dis-tribution system and its components will operate within component voltage limitations.
The motors are the limiting component under steady-state conditions as they are designed to run continuously at.9 per unit nameplate voltage.
Transient voltage drops due to the starting of motors were analyzed at each voltage level with no adverse effects.
This analysis assumed the prestart voltage to be that corresponding to the degraded 500 kV system and the load in parallel with the motor being started equal to the maximum continuous rating of the transformer to which it is connected less the running load of the motor being started.
Further, the impedance of the parallel load was conservat.ively assumed to decrease as the square of the bus voltage to analytically compensate for the additional.current drawn by induction motors upon decrease in voltage.
The minimum transient voltages obtained on the 4.16 kV, 460V and 230V levels were.86,.86 and.78 per unit, respedtively for a duration of approximately 5 seconds.
These transients are within motor and motor starter design capabilities, thereby having no adverse effedt on system operation.
The results of this analysis were used to reexamine under-voltage protective settings and establish that no spurious ~eparations of the safety buses from of fsite power would occur.
The 5 kV power cables that connect the 13.8/4.16 kV station.power transformers to the group and vital buses are the load limiting component in the distribution system.
The sixteen hour rating of the cable is utilized for the load th.at results from the concur-rent LOCA. Unit 2 a.nd Unit trip on Unit 1.
There is.sufficient margin between the cable rating and the*resultant load to allow for implementation of existing station procedures used during the events analyzed and thus, avoid overloading.
As indic.ated in the NRC letter of August 8, 1979;. tests had been previously run to correlate calculations with field conditions.
With Salem Units 1 and 2 and the 500 kV system in an existing mode corresponding to a given 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 voltage to obtain a calculated voltage profile and compare to actual measurements.
The calculations* and field measurements correlated within very reasonable accuracy, thus
I I
i.*
.1 Dir. of Nuc. Reactor Regulation 10-10-79 substantiating our assumptions and the method of calculation.
The results are given in Attachment l. Further, a test on a cold oOOO horsepower, 4.0 kV reactor coolant pump motor was conducted.
The bus voltage dropped 15% upon start of this motor.
No adverse effects were observed on other operating equipment.. The results of this test substantiate the original plant design basis.
The 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 offsite network that would violate GDC-17.
No potential exists for violation of GDC-17.
If you should have any questions, please do not hesitate to contact us.
Very truly yours, Feer:~~id4 General Manager -
Electric Pr6duction
- .~......
I
~r--*
500 kV Bus 13 kV Bus No. 11 Sta. Pwr.
4 kV Bus ATTACHMENT 1 Load SALEM GENERATING STATION, UNIT 2 VOLTAGE PROFILE
- FIELD MEASUREMENTS VS. CALCULATIONS No. 2Pwlr.u _J Sta.
I 4200 Measured i
Lumped 4 kV Running LOad 19.27 MVA 4 kV Bus 4160/480V 465-470 Measured 470 Calculated 460V BUS
. Lumpe 460V Load Running 580 KVA 235-239 Measured I
To Response to NRC Letter Jlii=gllacy of Station Electric Distribution 239.l calculat~
System Voltage -
Dated August 8, 1979 30V Bus