ML18100A871
| ML18100A871 | |
| Person / Time | |
|---|---|
| Site: | Salem  |
| Issue date: | 02/07/1994 |
| From: | Hagan J Public Service Enterprise Group |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NLR-N94013, NUDOCS 9402170304 | |
| Download: ML18100A871 (14) | |
Text
Public Service Electric and Gas Company Joseph J. Hagan Public Service Electric and Gas Company P.O. Box 236, Hancocks Bridge, NJ 08038 609-339-1200 Vice President - Nuclear Operations FEB 0 7 1994 NLR-N94013 United States Nuclear Regulatory Commission Document Control D~sk Washington, DC 20555 Gentlemen:
RESPONSE TO UNRESOLVED ITEMS FROM INSPECTION REPORT 50-272/93-82 & 50-311/93-82 SALEM GENERATING STATION UNITS NO. 1 AND 2 DOCKET NOS. 50-272 AND 50-311 on December 7, 1993, Public Service Electric and Gas Company (PSE&G) received NRC Inspection.Report Nos. 50-272/93:..82 and 50-311/93-82 for the Electrical Distribution System Functional Inspection (EDSFI) conducted from August 16 to September 3, 1993.
As requested by the NRC, the following attachment provides a schedule for resolution of the 13 Unresolved Items identified in this report.
If yo*u have any qliestions regarding this transmittal, please. do not hesitate to contact us.
Attachment (1)
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9402170304 6~858~72
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Document Control Desk NLR...,N94013 2
C Mr. T. T. Martin, Administrator - Region I
- u. s. Nuclear Regulatory Commission 475 Allendale Road King of Prussia, PA 19406 Mr. J. c. Stone, Licensing Project Manager U. s. Nuclear Regulatory Commission One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. c. Marschall (S09)
USNRC Senior Resident Inspector Mr. K. Tosch, Manager, IV NJ Department of Environmental Protection Division of Environmental Quality Bureau of Nuclear Engineering CN 415 Trenton, NJ 08625 F£B 0 7 1994
Attachment RESPONSE TO UNRESOLVED ITEMS FROM INSPECTION REPORT 50-272/93-82 & 50-311/93-82 SALEM GENERATING STATION UNITS NO. 1 AND 2 DOCKET NOS. 50-272 AND 50-311 Unresolved Item 93-82-01 a)
"The team noted that two transformers of each channel were fed by the same breaker at the 4kV bus.
These two transformers would not be electrically independent, and each of them is susceptible to unnecessary high switching voltage surges generated by the other transformer.
This voltage surge could exceed the Basic Insulation Level (BIL) of these transformers (25kV at the 4kV side and 10 kV at the low voltage side).
There was no surge protection on the 4kV vital busses, and no voltage surge study."
b)
"The licensee stated that there were four failures on the nonclass lE transformers and one failure on the vital transformer between 1990 and 1992.
As a result of-an analysis, the licensee determined that there was a lack of layer insulation between the high voltage winding layers 3 and 4, and planned to replace both the vital and nonvital transformers with higher BIL transformers."
Response
a)
A previous study was performed by Power Technology Inc.
which indicates that the failure mode suspected (i.e.,
failure of one transformer damaging the adjacent transformer) is unlikely due to the fact that the.
transformers are connected to the bus by ver~ short cables.
However, in the event that one of the two transformers is lost, the respective channel becomes inoperable.
Since Salem station only requires two out of three vital channels to shut down, the present design with the 4160/240 V and 4160/480 V transformers for each vital bus fed by the same breaker is acceptable.
Also, each transformer is provided with its own overcurrent protection.
b)
PSE&G plans to replace the ~ry type vital transformers with higher BIL rating on the following schedule:.
NLR-N94013 Transformer 2A, 2B, & 2C_*
4160/480 v -
1 Outage Date 2R7 4/93 BIL Comments 60 kV complete_
- 25 kV BIL
Transformer Outage Date BIL lA, lB, & lC lRll 10/93 60 kV complete*
4160/480 v 2A, 2B, & 2c 2R8 10/94 60 kV 4160/240 v lA, lB, & lC 1R12 3/95 60 kV 4160/240 v Unresolved Item 93-82-02 "The team reviewed the loading demands O*f the EDG. under various postulated design basis events.
The worst EDG loading given in the licensee's EDG loading calculation was EDG 2A in case B, LOCA plus loss of offsite power (LOOP) scenario.
The.EOG loading for the first 20 minutes was about 2814 kW and followed by 2841 kW for the remaining 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> 40 minutes, with power factor about 0.88 lagging.
This loading was just within the EOG 2-hour rating of 2860 kW; the team did not see any spare capacity for any future load increases.
The team noted the following deficiencies in the calculation:
- a. the calculation did not include all the intermittent loads, e.g., motor-operated valves (MOVs), which could be running during the first two hours following a postulated accidents;
- b. the calculation did not include all the small motor loads, which were controlled by their process signals.
These loads are: service water sump pumps (SWSP), EDG starting air compressors (EDG SAC), and RHR sump pumps (RHRSP);
- c. the load of the 115 Vac inverter, which supplies power to the instrument buses, was assumed to be 110% of the walkdown readings of the inverters.
There was no basis to support that these figures were the worst case inverter loadings during the accident condition; and
- d. the EDG load calculation did not consider load -
variation due to voltage and frequency variations."
Response
a&b) The assumption used for the intermittent loads is considered to be accurate. These process controlled loads are not likely to run at the same time and therefore, the loading tables for the generators should not change~.However, the fact that these loads are not NLR-N94013 2
c) d)
locked off and that they are process controlled, there is a remote possibility that they.could all run simultaneously.
There. should be sufficient margin within the 1/2 hour rating of the EDG to operate this equipment.
This margin is not required for the 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> or continuous ratings of the EDGs because these loads are intermittent type loads.
The inverter loading is not a significant issue with regard to the EDG loading because there was considerable conservatism in the calculation with regard to the loads used for the battery chargers.
PSE&G plans to more accurately reflect the battery charger loading in the EDG calculation and apply the margin gained to the inverter loadings.
The margin gained should allow the inverters t~ be loaded to their ratings in the EDG calculation.
The EDG calculation is a steady state calculation.
This assumes that the average voltage and frequency provided by the EDG will be the nominal values.
While it is true that if the voltage regulator and engine governor control voltage and frequency at their respective upper limits, the load on the EDG will increase.
This change in voltage and frequency cannot be considered the steady state or average condition.
There should be sufficient margin within the 1/2 hour rating to accept this short term bounding operating condition.
Therefore, this margin should not be required for the continuous rating.
PSE&G will revise the Emergency Diesel Generator loqd calculation (ES-9.002) by August 31, 1994, to include analysis of the above concerns.
Unresolved Item 93-82-03 "The team identified that the current EDG surveillance test procedure and Unit 2 technical specifications allowed the EDG to operate at a steady state at as low as 90% voltage (3744V), which is lower than the degraded voltage setpoint.
The licensee agreed to revise the surveillance test procedure and request a change to the technical specifications.
The team examined the past test results (S2.0P-ST.SSP-0003(Q) for EDG 2B, and S2.0P-ST.SSP-0004-(Q) for EOG 2C) and found the steady-state voltage of the EDG had been consistently maintained above the 95% level, i.e.,.
higher than 3952V~
The Unit 1 technical specifications did not specify any limit on the EDG running voltage."
NLR-N94013 3
Response
PSE&G requested a change to the technical specifications for Units 1 and 2 on September 30, 1993, to revise the minimum steady'state voltage of the EDGs to be greater than or equal to395'0 volts, which is greater than the degraded voltage.
setpoint.
The NRC approved this technical specification change as Amendment Nos. 148 and 126 to the Salem Unit 1*and saiem Unit 2 Technical Specifications, respectively, on November 30, 1993.
Appropriate surveillance procedures have been revised to *reflect this new minimum value for steady state EDG voltage.
Unresolved Ite~ 93-82-04 "In reviewing the walkdown records enclosed in the EDG loading calculation, the team noticed that there were two 230V rated motors (Service Water Building Ventilation fan lA and lC) at 248V and at 115% of the rated horse power.
When the bus was at its.upper limit.of 4500V, the terminal voltage of these two motors could be higher than 248V,_. and the fan-motor load could be even higher than 115% of rated HP.
The licensee agreed to review the overvoltage situation and would include an over voltage evaluation in the degraded vol_tage study. "
Response
The normal operating voltage range of the vital.buses is maintained between 4300 V to 4500 V (automatic load tap changers are provided on the transformers to keep the bus voltage in this range).
If the bus voltage goes above
- 4500 V, procedures exist that direct the operators to take actions to alleviate this over voltage concern.
This over
- voltage condition is not a significant safety concern because the Unit 2 480 and 240 volt tran.sformers are set in the nominal tap postiions.
This means that as long as the voltage is maintained at the 4KV bus at less than 110%, the voltage at the 240 and 480 volt buses will also be less than 110%, precluding any over voltage condition for the control relays.
PSE&G is in the process of implementing a major power distribution system modification.
Modification of the Unit 1 power system is complete and Unit 2 will be completed by end of the Eighth Refueling outage which is currently scheduled for the fall of 1994.
In the new configuration, the upper voltage limit will be controlled at 4400 v.
Calculations have been performed that prove that there are no over voltage conditions in the new configuration-.
NLR-N94013 4
Unresolved Item 93-82-05 "The team found the 4160V/480V transformer overcurrent protection was set at 300%.
The protection scheme would trip the transformer supply breaker for current at 300% or higher (due to tolerance of the relay).
This protection scheme did not fu*11y cover the full range of* the transformer damage curve.
The transformer was not protect.ad for. any overcurrent below 300% of full.load current.
Furthermore, the operator had no means to know that the transformer was overloaded because there was no current measurement at the 4160V side nor at the 480V side of the transformer, on the bus or in the control room.
In case such a failure occurred, the fault wouid not be isolated in time.
Eventually, this *fault would be isolated when it developed*into a severe fauit with fault current higher than 300%.
It was the team **s concern that transformer overloading could cause s*evere damage to or fire hazard in the 4160V switchgear cubicle where the transformer was located.
The license agreed to evaluate this issue to determine whether the 300% setting should be revised or other appropriate corrective actions should be taken."
Response
Design Change Packages (DCP) will be prepared by 3/31/94, to revise the setting of the transformer overctirrent relays to provide for optimal protection of the tranformers.
These DCPs will be implemented during the Twelfth Refueling Outage for Unit 1 and the Eighth Refueling Outage for Unit 2.
Unresolved Item 93-82-06 "The team reviewed the UPS purchase specification (No.
18310-E035A, dated November.4, 1988).
Paragraph 3.6.3 of this document specified that the total output voltage harmonic content should not exceed 5% of the fundamental voltage.
Nonlinear load applied to the instrument bus could affect the amount of harmonic distortion.
- The licensee stated that the total output voltage harmonic content was never verified after installation.
Recent inspections by the NRC on other sites that had the same requirement (5%)
indicated that this value exceeded 10% because of nonlinear load applied to the output.
The licensee agreed to verify this value: and, if the measured value exceeds the specified value, evaluate the adverse effect on safety-related instrumentation."
Response
PSE&G is in the process of developing an acceptance criteria for harmonic distortion at the system level.
This action includes obtaining instrument performance data that is not NLR-N94013 5
readily available.
Based on the results of this activity, measurements will be taken and corrective actions will be implemented as necessary to ensure continued reliable control/instrument circuitry operations.
A preliminary assessment of this* issue indicates that.most of the critical safety related instrumentation at Salem utilizes DC power supplies fed from the vital AC system.
It is our technical opinion.that this.design feature would significantly reduce the susceptibility of the instrumentation to effects associated with harmonic distortion of the AC source.
In addition, PSE&G has reasonable assurance that adverse effects on saf ety~related
- instrumentation, if any,- are minimal due to no apparent trend or record of experienced instrumentation failure~ due to AC power quality related issues..
On the basis of _the above discussion, PSE&G will research industry data, and develop the harmonic distortion acceptance criteria by May 30, 1994.
PSE&G will then take system measurements and implement corrective actions as required.
The schedule for this activity will be aligned with the station operating schedule.
unresolved Item 93-82-08 (The NRC performed a review of the EDG fuel oil storage tank curve and came to the following conclusion.)
"The tank volume curve calculations, S-C-YAR-CDC-095 Rev. 1, which provided conversion of tank volume to height, failed t6 account for the unusable volume (vortex, -imperfection of fabrication and installation, etc,) and level instrument error.
Since this calculation also applies to the other 28 tanks for both units, the licensee agreed to review the calculation to* ensure that unusable volume and level instrument error were considered in obtaining the total usable volume for those tanks."
Response
PSE&G has performed a review of safety-related tank internals and has noted that anti-vortexing baffles were installed in most tanks to alleviate the vortexing effect.
In the case of the Diesel Fuel Oil Storage Tank, where anti-vortexing devices were noticeably a:Qsent, PSE&G ha-s studied the vortexing effect on* the fuel oil storage level and concluded that it is minimal.
PSE&G believes that the*
identified concern is a result of lack of consistent, documented criteria for tank sizing.
NLR-N94013 6
PSE&G will formulate a technical standard for the sizing of all tanks and apply the standard criteria to prepare a minimum volume tank calculation to clearly document the consideration for all factors including vortexing, level instrument.error, etc.
PSE&G will also conduct a review of all Salem safety-related tanks based on_ the above standard and will summarize the results of the review in an engineering evaluation.
PSE&G will complete this evaluation by December of 1995, except for the Diesel Fuel Oil storage
_Tank which will be completed by June of 1994.
PSE&G will also address level instrument inaccuracies on technical specification tanks *through the design basis reconsitution effort on setpoints that is currently scheduled for completion by December of 1995.
Unresolved Item 9.3-82-10 "The team reviewed evaluations S-l-CAV-MDC-0678 and S-2-CAV-MDC-0696 (Switchgear and Penetration Area Ventilation) and concluded that the equipment in the switchgear areas would be operable, considering that the ambient temperatures were expected to below the design ambient temperature of 95°F in the coming months.
The iicensee made a commitment to complete the calculations, analytical/design evaluation, etc. prior to the month of May 1994 (before the onset.of high sustained outdoor temperatures)."
Response
PSE&G is in the process of calculating the heat loads in the switchgear room during normal and accident conditions.
Upon completion of the heat load calculation, PSE&G will finalize the switchgear room heatup calculations.
If the calculated temperature is qetermined to be higher than 105°F (the maximum design temperature for the switchgear room),.PSE&G will evaluate the effects of the increased temperature on the electrical equipment in the switchgear area.
PSE&G will complete these actions by 3/31/94.
Unresolved Item 93-82-11 "During the walkdown on August 16, 1993, the team observed that the nonsaf ety-related MG sets were located in the area which houses all three 4kV vital buses.
The team expressed concern that MG set flywheel failure could disable two out of three 4kV vital buses.
Two vital buses were required to achieve safe shutdown.
This licensee did not have informa~ion to address this concern.
The licensee agreed to perform an evaluation/study to address this issue."
NLR-N94013 7
Response
PSE&G issued engineering evaluation S-C-RCS-SEE-0866, "Rod Control System MG Set Flywheel Failure," on 1/12/94.
This evaluation concludes that based on information provided by Westinghouse that the flywheels, which were designed, procured and fabricated un'der closely controlled quality standards, have such a high degree of structural integrity that the concern raised with respect to flywheel disintegration is not credible.
The probability of flywheel failure is sufficiently small that the consequences of failure need not be protected against.
Unresolved Item 93-82-12 "The 18-month test procedure for Unit 2 EDG specified an EDG load equal to or greater than its 2 hour2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> rating of 2860 kW for at least 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br />.
The team reviewed the test data of the 18-month (endurance) tests of EDG 2A.
The test data indicated that the EDG was loaded consistently between 2920 and 2950 kW for two hours in each test.
This issue was discussed with the licensee:
The licensee's position on this issue was as follows.
The temperature and other variables observed during these tests were well within the normal operating range.
The inspections, which took place 18 months after an endurance test, did not reveal any unexpected wear.to the diesel engine parts that would be expected to indicate wear.
Additionally, the licensee contacted the EDG vendor concerning the consequences of these tests.
On October 27, 1993, the licensee called to inform the team that preliminary analysis, by the vendor, of the test data indicated no damage to the EDGs.
The licensee was also considering a revision of the technical specification requirements and the test procedures implementing these requirements."
Response
PSE&G performed an extensive inspection on 2C EDG during the Salem Unit 2 forced outage in December of 1993, to substantiate a preliminary analysis performed by the EDG vendor that the past overloading of the Unit 2 EDGs had no impact on EDG operability.
The 2C EDG was subjected to the most severe overloading during past surveillance tests (the average 2 hr kW loading from the past three surveillance tests for the 2C EDG was 2984 kW compared to EDG vendor's 2 hr rating of 2850 kW).
The inspections were assisted by a representative of the EDG vendor.
The inspection (conducted under work order no. 931202257) encompassed sixty-six (66) inspection activities covering more than 50%
of the diesel power train [this is more than the manufacturer's normal requirement of 10% sampling inspection of the power train following a potential overloading NLR-N94013 8
situation].
The inspection effort included both visual and magnetic-particle testing (MT) of the following components:
Cylinder heads (Inspected & Hydrostatically Tested)
Pistons (Skirt and Crown)
Piston Rings Wrist Pins Connecting Rods Connecting Rod Bearings Bearing Caps Rod Bolts The above inspection indicated satisfactory results with no indication of distress or abnormal wear.
Additionally, 3R connecting rod was checked for parallelism, bend/twist in accordance with manufacturer tolerance~ It should be noted that the wrist pin is most sensitive to the overloading stress.
The cylinder intake & exhaust valves, seat areas, and fire deck were all checked with.no sign of overheating and erosion.
The crankshaft was visually inspected.
After diesel re-assembly, the EDG was re-tested and the results were satisfactory.
Our analysis further indicates that the maximum firing pressure during the overloading stages was below 1950 psig.
This is under the manufacturer's ceiling pressure of 2100 psig, which is reco:m:fnended in the Diesel Technical Manual and was subsequently discussed with the diesel manufacturer.
With the results obtained above, PSE&G believes that the Unit 2 EDGs were not adversely affected by past overloading during surveillance testing.
PSE&G will summarize our analysis in an engineering evaluation which will be completed by June.30, 1994~
Unresolved Item 93-82-13 "The team noted that many of the safety-related molded case*
circuit breakers (MCCB) were also used as isolation devices, separating safety-related buses from nonsaf ety-related loads.
If these MCCBs do not trip as required, a fault in the nonsaf ety-related load may cause the feeder breaker to trip, thus losing the whole train, affecting operation of many safety-related loads.
Many of the safety-related ~CCBs had not been current-tested ever since they were installed during the construction stage more than 15 years ago.
Recently, the NRC issued an Information Notice (IN 93-64, "Periodic Testing and Preventive Maintenance of MCCBs,"
issued August 12, 1993) discussing MCCB failures during testing and addressing the necessity of periodic testing of MCCBs.
The licensee agreed to evaluate the situation at Salem to determine their position regarding periodic test programs of MCCBs.
NLR-N94013 9
Response
Presently, PSE&G is periodically testing, per technical specifications, all Molded Case Circuit Breakers (MCCB) protecting containment penetrations.
As a result of NRC Information Notice 93-64, PSE&G is developing a MCCB database for the installed MCCBs, in particular the MCCBs used for an isolation device between vital and non-vital equipment.
This database development will be completed by 4/29/94.
PSE&G will m~ke a determination on testing program for MCCBs by 5/13/94.
Unresolved Item 93-82-15 "During review of past. surveillance test,.as well as through direct observation of the station.vital batteries, the team found that the lC and 2c, 125 Volt batteries operate a~ a temperature range much greater than the other station batteries.
This is because these two batteries are in separate enclosures whe.re the environment is not specifically controlled.
From the surveillance test results reviewed, the lC battery had an operating range from 70°F to 96°F.
The 2C battery had similar operating temperatures.
The other station vital batteries generally remained within a three or four degree band from the nominal operating temperature of 77°F.
The licensee's procedures stated that the acceptable operating temperatures for the batteries are from 60°F to 105°F.
While no unacceptable condition was *observed, the team was concerned that the extreme temperatures experienced by these two batteries may be leading to accelerated aging.
The licensee's independent EDSFI also reviewed this issue; however, there were no battery failures at that time.
Therefore,.while the licensee's assessment noted the difference in operating temperatures for the station batteries, no significant finding was made and no co~rective actions were deemed necessary.
Based 6n the failure of cell No. 47 and the operating characteristics of the lC battery, the team was concerned that accelerated aging may be occurring, warrant~ng other actions by the licensee to ensure the continued operability of the battery.
One indicator of this was the build up of sediment in the jar bottoms for this cell, as well as for*
five other cells in the same battery.
The licensee stated that actions would be taken to identify the root cause of the failure of cell No. 47, especially considering the
- effect of operating temperatures.... The long-term corrective actions for the lC and 2C, 125 volt batteries remain unresolved based on licensee assessment of the aging effects due to the-operating temperatures experienced by these components."*
NLR-N94013 10
Response
Presently lC &.2C batteries operate in a non-air conditioned room and are subject to ambient conditions dictated by the weather.
Temperatures of the rooms vary depending upon the outside temperatures.
Based on the review of quarterly battery surveiliance data for 1991, the highest and lowest temperatures recorded in these rooms are 95°F and 65°F, respectively.
As a result, there is rio direct correlation or quantification between the length of time that _the batteries will operate in a high temperature scenario versus a low temperature condition and the effects on degrading the batteries versus increasing their life.
In accordance with the battery manufacturer (C&D), the operation of batteries in an increased temperature will decrease the life expectancy of the battery cells.
.rt is generally stated that for every l8°F above 77°F will decrease battery life by 50%.
This battery manufacturer also claims that lower than normal operating temperatures have the opposite effects on the batteries.
Therefore, at lower temperatures the batteries will last longer (at float voltages).
This implies that the varying battery room temperature has some effect on battery life over an extended period of time, but does not create the possibility of a sudden catastrophic failure.
The existing battery surveillance program, at both Salem stations, adequately monitors the battery status which will ensure that any degradation of the battery life due to varying temperatures will be detected before it leads to failure of the battery.
Unresolved Item 93-82-16 "In examining the starting. transient voltage and frequency traces of the surveillance test results on the Unit 2 EDGs, the team noted the frequency transient fell below the 95%
minimum value recommended by Regulatory Guide (RG) 1.9.
However, the licensee did not fully commit to RG 1.9.
The transient voltage was above the 75% minimum value recommended by RG 1.9.
In addition, the licensee provided the team with copies of the EDG surveillance test records on the Unit 2 EDGs.
The team compared the above test results with the load demand kW and kvar profile during EDG sequencing, and estimated that the EDG would be capable of picking up the Class lE loads as required.
The licensee agreed to perform the auto-sequencing test of the Unit -1 EDGs in the *next refueling outage surveillance test to demqnstrate that the transient voltage and frequency profiles are within the acceptable limit."
NLR-N94013 11
Response
During lRll, Engineered Safety Feature (ESF) Mode-Op tests were performed in accordance with procedures Sl. OP-ST. SSP-0002 (Q) 11 1A Vital Bus, 11 Sl. OP-ST. SSP-0003 (Q) 111B Vital Bus, 11 and Sl.OP-ST.SSP-0004 (Q) "lC Vital Bus. 11 At no time did any Emergency Diesel Generator (EDG) voltage fall below 75% (3120 VAC) of nominal generator voltage when the largest single load (i.e., service water pump) as well as the other sequenced loads were started.
All EDG generator voltages returned to 90% (3744 VAC) of nominal generator voltage within 60% (2.4 seconds) of the largest load's load-sequence time of 4 seconds.
At no time did lA EDG or lB EDG frequency fall below 95% (57 Hz) of nominal generator frequency.
lC EDG frequency dropped b~low 57 Hz*
and took more than 2.4 seconds to.recover, however, all lC EDG loads started and accelerated to rated speed.
Based on the above test results, Unit 1 EDGs' voltage and frequency response met the intent of Regulatory Guide 1.9.
The fallowing table is a summary of the above recor_der chart test results.
EOO/I.oad Test Min. Freq Freq Resp:>nse* Volt ResPC>nse*
1A Blackout 57.40 Hz 1.47 Sec 0.85 Sec 1A Target Load*
58.20 Hz 0.94 Sec 0.91 Sec 1B Blackout 57.30 Hz 1.62 Sec 1.16 Sec
~ Target Load*
57.36 Hz 1.62 Sec 1.26 Sec lC Blackout 56.56 Hz 2.57 Sec 1.34 Sec lC Target Load*
58.16 Hz 1.05 Sec 1.38 Sec
- Target Load is the load the generator will see just prior to starting the largest load based on EDG Load Study Calculation ES-9.002.
The frequency response is the time from when generator frequency decreased below 58.8 Hz to when generator frequency recovered above 58.8 Hz.
The voltage response* is the time from when generator voltage decreased below 3744 VAC to wnen generator voltage recovered above 3744 VAC.
NLR-N94013 12