ML18067A795
| ML18067A795 | |
| Person / Time | |
|---|---|
| Site: | Palisades  |
| Issue date: | 11/21/1997 |
| From: | Bordine T CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.) |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| TAC-M94378, NUDOCS 9712020213 | |
| Download: ML18067A795 (5) | |
Text
~---------~--* -------------------------------
A CMS Energy Company November21, 1997*
U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Thomas c. Bordlne Manager Licensing DOCKET 50-255 - LICENSE DPR PALISADES PLANT ELECTRICAL POWER SYSTEM TECHNICAL SPECIFICATIONS CHANGE REQUEST (TAC NO. M94378) - RESPONSE TO A REQUEST FOR ADDITIONAL INFORMATION On December 27, 1995, Consumers Energy submitted, for review, an electrical power system technical specifications change request. Supplemental information was also submitted by Consumers Energy on September 4, 1996, and June 27, 1997.
Subsequently a request for additional information (RAI) dated November 13, 1997, was received. This letter provides the response to that RAI.
The attachment to this letter lists each individual request for information and provides the Consumers Energy response.
SUMMARY
OF COMMITMENTS This letter contains one new commitment and no revisions to existing commitments.
The commitment is:
By April 30, 1998, Consumers Energy will perform a documented evaluation of the adequacy of existing plant procedures concerning a loss of load scenario when the Palisades emergency diesel generator is paralleled to the grid. Plant procedures will be revised if determined necessary by the evaluation.
Thomas C. Bordine Manager, Licensing CC Administrator, Region Ill, USNRC Project Manager, NRR, USNRC NRC Resident Inspector - Palisades Attachment 1.. >,*. :J r7 0
. I -- \\_)
9712020213 971121 - - -
PDR ADOCK 05000255 P
PDR I If Ill/ f 1111f1111 ]1/llJllll j/lllllll If 11 Palisades Nuclear Plant
- 27780 Blue Star Memorial Highway
- Cove;t, Ml 49043
- Tel: 616 764 2913
- Fax: 616 764 2490
ATTACHMENT CONSUMERS ENERGY COMPANY PALISADES PLANT DOCKET 50-255 Response to Request for Additional Information (NRC Letter dated November 13, 1997)
Electrical Power System Technical Specification Change Request 3 Pages
ATTACHMENT Palisades Nuclear Plant Response to Request for Additional Information (NRC Letter dated November 13, 1997)
Electrical Power System Technical Specification Change Request NRC letter dated November 13, 1997, requested additional information with respect to Consumers Energy's December 27, 1995, Electrical Power System Technical Specification Change Request submittal. Below is each request for additional information and the Consumers Energy response.
NRG Request:
- 1.
The proposed emergency diesel generator (EOG) full load rejection test surveillance requirement (SR) includes an acceptable voltage limit of 4000 volts during and following the load rejection. Are all of the EOG instrumentation circuits and associated relays capable of withstanding this high voltage?
Consumers Energy Response:
All of the EOG instrumentation circuits and associated relays are capable of withstanding the high voltage encountered during the proposed EOG full load rejection test. The diesel generator, governor and voltage regulator manufacturers were contacted and they *advised that a short duration spike of 4000 volts should not affect the function of EOG instrumentation and associated relays. In addition, the metering provided with the diesel generator has overload protection of much higher ratings than the 4000 volt value. The digital watt meters are the weakest link in terms of voltage rating for the EOG instrumentation and controls. The digital watt meters are protected to 200% or 240 VAC. (4000 volts at the generator output breaker translates to 200 VAC at the watt meters.)
It should be noted that the upper limit for voltage (4000 volts) was chosen by Palisades as a conservative value for equipment protection; representing sufficient margin above actual expected voltages. Previous loss of load testing experience has shown maximum values near 2900 VAC. One diesel generator was recently tested during normal diesel generator startup and the peak voltage observed was 2890 VAC.
page 1 of 3
~. *-"
NRG Request:
- 2.
Regarding the proposed 24-hour EOG load test SR:
- a.
With the EOG paralleled with offsite power, what effect would a plant trip have on the Class 1 E electrical distribution system?
- b.
What is the offsite power source for the opposite train during the test?
- c.
Is there a load limiter on the excitation system and governor?
Consumers Energy Response:
- a.
When the plant trips and the EOG is in the parallel mode of operation, circuit relaying will actuate to open the EOG output breaker causing a full load rejection. Relays then provide a 1.5 second delay before allowing the EOG output breaker to reclose for load sequencing if offsite power is lost. If offsite power is not lost, the EOG continues to run in stand-by with its output breaker open.
Failure of these circuit relays are discussed below.
Case 1:
In this case, the condition is examined where the EOG is operating in parallel to the grid with the plant on line, and the main turbine generator trips with the EOG output breaker failing to open.
During normal plant operation the safeguards transformer provides power to both Class 1 E emergency buses. The safeguards transformer is directly connected to the grid via the Palisades switchyard 'F' Bus. The safeguards transformer has an automatic tap changing feature which will automatically adjust output voltage. Power to the emergency buses during plant trip should not be affected as no fast transfer of emergency bus supply power occurs; the safeguards transformer maintains supply to the emergency buses.
Loss of the main generator could, however, cause reactive load changes on the grid which could propagate through the safeguards transformer to the paralleled EOG. The impact on the EOG has been evaluated and the effect on the EOG voltage regulator is minimal. The current voltage control band on the diesel generator is approximately 2200 to 2700 VAC while in parallel. These values translate to grid voltages of 316,000 to 388,000 volts, which are far outside the range of grid voltages experienced at Palisades. Additionally current limiting resistors are an integral part of the voltage regulation protection.
page 2 of 3
...J'....
The primary concern is the EOG windings due to the voltage offset between the EOG reference and grid voltage. This offset could result in EOG operation outside of the nameplate specified power factor ratings.
However, over current relays on the EOG output breakers are set for EOG overload protection. Also, an additional relay is set at 100% of diesel generator rated output for annunciation. This annunciator is provided to alert operators of an overload condition. Additionally, all operators are trained to recognize how reactive power and frequency changes on the grid, caused by either Palisades main turbine generator or offsite influences, affect a paralleled EOG.
Case 2:
Operation of the EOG while paralleled to the grid and the plant is offline.
This condition may exist with either the safeguards transformer, station transformer or start-up transformer as the power source for the emergency buses. The station and start-up transformers are not tap changing and, therefore, changes in grid reactive loading may have greater impact on the diesel generator. In either case, voltage regulator protection and breaker protection are the same as discussed above in case 1.
In both cases, when the EOG is paralleled to the grid the EOG is considered inoperable and credit is taken for the standby EOG.
Palisades believes, however, that a loss of load scenario with the EOG paralleled to the grid has some likelihood of occurring. Therefore, this condition will be evaluated further to determine if existing procedures provide the operators sufficient guidance for actions to be taken should such an event occur.
If necessary, procedures will be revised as a result of this evaluation.
- b.
During normal plant operation the offsite power source for the opposite train during the test is also the safeguards transformer. This is considered the most reliable source of power to the emergency buses.
- c.
The EOG does not feature a real or reactive load limiter. EOG protection is provided by an approximate 3% speed droop, an approximate 5% voltage droop, over current and differential relay protection, and the aforementioned relaying which will trip the EOG output breakers on a main generator trip.
page 3of3