ML20052A556
| ML20052A556 | |
| Person / Time | |
|---|---|
| Site: | Rancho Seco |
| Issue date: | 04/21/1982 |
| From: | Mattimoe J SACRAMENTO MUNICIPAL UTILITY DISTRICT |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| TAC-12746, NUDOCS 8204280456 | |
| Download: ML20052A556 (2) | |
Text
~
g' SACRAMENTO MUNICIPAL UTILITY DISTRICT O suuo 95813; (916) 452-3211 April 21, 1982 oI N S
RECEgygg 9
DIRECTOR OF NUCLEAR REACTOR REGULATION Apg 7 ggQ!pakh{
ATTENTION JOHN F STOLZ CHIEF OPERATING REACTORS BRANCH 4 g
U S NUCLEAR REGULATORY COMMISSION WASHINGTON D C 20555
//
g fa DOCKET 50-312 RANCHO SECO NUCLEAR GENERATING STATION UNIT NO 1 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGE We are pleased to provide the following information on the status of our over/under voltage study and modifications as requested by Mark Padovan in a recent telephone conversation.
- The District is presently performing a study to verify that overload heaters will not cause spurious trips as a result of operating at the degraded voltage.
The District will replace any motor control center overload heaters that our analysis indicates could cause a trip during degraded grid conditions. These changes, if required, will be made during the 1982 outage.
- As stated in Part A of Enclosure 1 to our letter of February 17, 1981 to Mr. Robert W. Reed, we have:
- 1) Changed the loading segr.ence of the diesel generator room supply and exhaust fans from load group 2 to load group 3.
- 2) Changed the setpoint on the inverse-time undervoltage relays to 3744V.
- 3) Issued special orders to plant operators to describe operator action at degraded voltage conditions.
- 4) Modified the control circuit for the control room air condi-tioning unit.
l od 8 2 0 4 2 8o45G,
' * ' 0 as meroc svsuu sonsc om 1m eum
,s n,,, m c,
0 JOHN F STOLZ April 21, 1982 We still have the following modifications to make during the outage scheduled for September 1982.
- 1) Install the 2 out of 3 coincident logic circuits.
- 2) Set the undervoltage relays at 3771V.
- 3) Set the overvoltage relays at 4580V.
- 4) Limit plant operation if the switchyard voltage is less than 214KV.
- 5) Block automatic start of the condensate pumps on a turbine trip.
- 6) Modify the control circuit for the upper dome air circulating fan motors.
- The District is installing capacitor banks to add 65 MVARS to the
~
system which calculations show will keep our switchyard voltage i
above 214KV. All equipment is on order with delivery promised by I
June 10, 1982.
If this date is good, installation should be complete by the end of June.
- Last year we experienced two events (Reportable Occurences 81-34 and 81-39) where the grid voltage dropped below 218KV.
In the first event, the duration was 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br />.
In the second, we were below 218KV for 3 hours3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br />. The events and conditions in PC&E's system that resulted in the degraded voltages were extreme cases with a low probability of reoccuring.
Both of these events occurred when Rancho Se s was shutdown.
With the plant operating, we would not expect to ever see voltages below 218KV. The only modes we would expect to see the plant operating between 218KV and 214KV would be with the plant shutdown or starting up.
In these modes, the plant conditions that resulted in the low equipment terminal voltages which we calculated, would not be present. Therefore, we do not feel there would be any impact on the equipment because we do not reasonably expect the equipment to operate at the voltages we calculated.
We trust this provides the information to satisfactorily complete your review of our analysis of the adequacy of station electrical distribution voltages. If va can be of further assistance, please call.
i l
Mattimoe Assistant General Manager and Chief Engineer 1
i i
w 9
9w-
-v
-y e
---wg-7,&----d-9---
9m
-ev---g-- -
-v r--w---
v w-w v--
g
- -----i w
w
-we-r-y