ML20043F664

Training Material for E-111 Emergency Diesel Generator Course, Chapter 11 (3-16), Qualification, Site Acceptance and Survillance Testing

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Issue date:	02/12/2020
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Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing

11. QUALIFICATION, SITE ACCEPTANCE 6. Comments on the relevance of this AND SURVEILLANCE TESTING material to EDG selection/operation.

Learning Objectives NOTE: Principle design and application criteria for EDG units in nuclear power The primary objectives for this lesson are to plants are listed in Clause 4 and Table 1 of present the tests that EDGs are subjected IEEE 387-1995. Chapter 1 of this Manual to: (1) during their initial "type qualification" introduced the fundamental goal of 4000 for nuclear service, (2) by the EDG supplier, EDG starts and 6000 operating hours over a upon installation at the site, to demonstrate service life of 40 years. Important design compliance with the purchase contract, (3) criteria include the maximum and minimum as part of the licensee's pre-operational temperatures and humidity to which the tests to verify performance and develop system will be exposed, seismic response baseline data, and (4) during regular spectra, radiation, barometric pressure surveillance runs by the licensee. A typical (altitude), potential contamination of intake surveillance run will be outlined, including air or support systems by salt spray/sand/

the control of KW and KVAR load with the dust, service water quality and temperature.

EDG connected to the grid. To reinforce this Additional relevant factors include the effect material, the lesson will then conclude with of potential events such as severe weather some comments about EDG selection, plus and possible actuation of the fire protection operational examples that help explain the system. The focus of this Chapter is on relevance of these tests to actual EDG testing but some of the above design operations. criteria are factors in the case histories discussed in other parts of this Manual.

Upon completing this lesson, students will have a better understanding of: 11.1 EDG Type Qualification Tests for Nuclear Service

1. How EDGs are type-qualified for nuclear power plant service. In order for a diesel generator to be used as an on-site emergency standby power source

2. Installation, break-in run, inspection, at a nuclear power plant, it must first be and full load run by the EDG supplier. "type qualified" for that service by successfully passing rigorous performance

3. The licensee's pre-operational test tests and analyses to prove it can perform program to verify EDG performance its intended function. Regulatory Guide 1.9 and establish critical baseline data. (now Revision 4, March 2007) contains the basic requirement for that and IEEE 387

4. The licensee's ongoing surveillance (1995 edition) provides detailed guidance.

testing of their diesel generators. Prior qualification of an EDG of similar design is permitted to be used to reduce the

5. A typical EDG surveillance run by the testing and analysis required. Analysis is licensee, including control of KW and most often used when testing is seen as KVAR loading when on the grid. impractical or unneeded.

Rev 3/16 11-1 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing The initial "type qualification tests" for EDGs 1. Carry load equal to continuous rated are listed and discussed in Clause 6 of IEEE load for time required to achieve engine 387-1995, "Standard Criteria for Diesel- temperature equilibrium, followed by:

Generator Units Applied as Standby Power Supplies for Nuclear Power Generating 2. Carry the short-time rated load for 2 Stations." Diesel generator qualification hours and the continuous rated load for tests may be performed by the manufacturer 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br />. These different loads are or by an independent third party supplier. permitted to be applied in either order.

The latter arrangement is most likely due to the manufacturer of the engine-generator 3. Complete a load rejection test at the set not maintaining an approved 10 CFR 50 short-time load rating. Speed increase Appendix B quality assurance program. shall be less than 75% of the difference between nominal speed and the over-Qualification is normally completed by the speed trip set-point, or 15% over the manufacturer, prior to delivery of EDG units nominal (60Hz) RPM, whichever is less.

to the plant site. In some 1970's vintage plants, part / all of the EDG type qualification 4. Complete light/no-load test equal to the testing was conducted on-site. This was design light load, for allowed duration.

because IEEE 387 type qualification tests (Follow with 50% load for 0.5 hour5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />.)

were not formally endorsed by Regulatory Guide 1.9 until after the EDG systems were Start and Load Acceptance Tests:

manufactured and delivered to those sites.

Modified qualification testing was agreed to This is a very intense and grueling portion of by the licensees and performed on-site. the qualification tests. It requires starting and loading an EDG, or group of EDGs of 11.1.1 Three Basic "Type Qualification" the type being qualified, to verity the Tests for Nuclear Service EDGs capability to start and accept load within the time permitted by the plant design basis. A The tests outlined in Clause 6 of IEEE 387- total of 100 starts are performed, with zero 1995 will be covered in more detail later in failures permitted. (Previous editions of this this Chapter. The present discussion will Standard required 300 starts, with no more serve to introduce the three basic tests that than 3 failures.) If multiple engines are are used to verify the ability of an EDG to used, to speed up the testing, each engine perform its design basis mission. They are: must be tested for Load Capability, and Margin (the latter test is discussed on the Load Capability Tests: next page). Additional test criteria can be found in Clause 6.2.2 of IEEE 387-1995.

These demonstrate the EDG's ability to carry specified loads, at rated power factor, This effort can also be challenging to the test for the times indicated, to successfully reject facility, as it is very labor intensive and takes a heavy load, and also to operate at very weeks (or even months) to complete, light load (or no load) as specified by the depending on any problems or failures. An manufacturer. The tests include: overview of these tests follows:

Rev 3/16 11-2 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing

1. Start and achieve specified voltage and Margin Tests (transient conditions):

frequency within the required time.

This is a series of extra high stress tests

2. Immediately accept a single step load intended to demonstrate that the EDG has a equal to or greater than 50% of the performance safety margin for that plant's continuous kilowatt (KW) rating. design. It requires two or more loaded run tests applying loads greater than the most

3. At least 90 of these tests shall be with the severe step load in the plant design profile, EDG initially at warm-standby, with lube including step changes above a base load oil and water jacket temperatures being (any steady point on the loading profile).

kept at or below the values The limiting case (worst case) step change recommended by the mfr. After load is over base load, as defined by the design applied, run until temperatures are load profile, shall be demonstrated.

stabilized at normal levels for the load.

"Worst case" is not necessarily the largest

4. At least 10 of these tests shall be with the single step load, as the most severe step engine at its normal operating may be a smaller load applied as the EDG's temperatures for the load ("hot start"). full-load capability is approached. However, a margin step load at least 10% greater than

5. Any failure requires a design review, the magnitude of the most severe single-corrective action, and continuation of the step load within the load profile is deemed tests until reaching 100 consecutive sufficient for the margin test. The criteria for starts without failure. margin tests are:

NOTE: Allowance is made to disregard any 1. Demonstrate the ability of the generator, test start categorized below, and resume the exciter, and automatic voltage regulator test sequence without penalty: to accept the margin test load (usually a low power factor, high inrush starting A. Unsuccessful attempts that are clearly current to a pump motor), without the result of operator error. generator instability resulting in voltage collapse or inability of the voltage to B. Tests performed to verify a scheduled recover.

normal maintenance procedure.

2. Demonstrate the ability of the engine and C. Tests performed for troubleshooting its speed-regulating governor to accept purposes, defined as such in advance. that load without stalling, and to recover to normal operating speed.

D. Successful start attempts which were terminated intentionally, without loading. NOTE: Frequency and voltage excursions recorded during this test may exceed those E. Failure of any temporary service system values specified for the plant design load, as or any temporary hookup that will not be this test load should never be reached in the part of the permanent EDG installation. course of normal emergency service.

Rev 3/16 11-3 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing 11.1.2 Additional EDG Evaluation by seismic event. Seismic testing shall be Test or Analyses followed by functional testing to verify the relevant principle design criteria covered in Aging of Components and Assemblies: Clause 4 of IEEE 387-1995.

Clause 6 of IEEE 387-1995 introduced 11.1.3 Analysis / Test of Design Change comprehensive evaluation of ageing over to EDG Previously Qualified the design life of the EDG plant. Those components and assemblies required to Any design change or modification to a enable the unit to meet its design previously qualified EDG must be tested capabilities were deemed "safety-related." and/or analyzed "as needed" to assess the Examples include starting air solenoid impact on performance. IEEE 387 requires valves, the governor, functionally required that changes be analyzed to determine if the gaskets / seals for which failure (leakage) degree of change is major or minor:

would degrade performance, and electrical cable (discussed in a subsequent chapter). Major changes to a qualified EDG, such as a difference in the number of cylinders, Other, nonsafety-related components and stroke, bore, BMEP, running speed, or how assemblies still require verification that they the engine-generator is configured shall will not degrade a safety-related function. require requalification (as if a new design).

This may be done by testing, analyses, or a combination of test and analysis. Minor changes to a qualified EDG, such as component parts substitution, shall be For those components and assemblies that qualified by analysis, or testing, or both.

were classified as safety-related, their age-related failure mechanism potential must be The category assigned to a (proposed) evaluated. Those with significant potential design change or modification is influenced for age-related failures must be qualified by by the use of that part or design feature in testing (preferred), analysis, or both. The other EDGs (especially of the same series) components with a qualified lifetime less and by experienced engineering judgment.

than the EDG system life objective shall have a maintenance / replacement interval 11.2 "Factory" Production Testing defined. If aging by test is used, it must be followed by seismic qualification to meet Clause 5 of IEEE 387-1995 requires that IEEE 344-1987. EDGs have "factory" production tests as described below. However, these may be Seismic Qualification Requirements done by the manufacturer or the supplier, at the factory, at the assembler's facility, or on-Seismic qualification per IEEE 344-1987 is site after delivery to the NPP. Typically the required for all safety-related components. manufacturer will have run the engine briefly Nonsafety-related components require at the factory, followed by a lower end check analysis / test to show they will not degrade for potential problems, but the following the EDG's safety-related function during a tests are most often done on-site:

Rev 3/16 11-4 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing

1. Initial "break-in" run as recommended

• Valve train set-up and clearance.

by the manufacturer.

• Fuel injection component checks.

2. Load the engine as follows, using 4. Engine speed-regulating Governor set-either a dynamometer or generator: up and calibration.

(These tests may be run in any order).

One hour at 50% of the continuous 5. Engine over-speed Governor set-up and rating, one hour at 75%, two hours calibration.

each at 100% and 110%. Log data per 5.2.1 of IEEE 387-1995. Set and 6. Engine trip and alarm relay calibrations.

check engine-mounted alarms and shutdowns. Perform and document 7. Generator internal checks, including:

post-test inspections per mfr's spec.

• Rotor to stator gap and concentricity

3. Generator shall be tested per NEMA

• Insulation resistance (megger test)

MG 1-1993.

• Slip ring and brush alignment, condition, and brush tension check.

11.3 Initial On-Site Set-up of EDG

8. Automatic voltage regulator set-up and Factory/supplier field service and utility calibration.

personnel conduct on-site inspections, adjustment, and testing to assure the EDG 9. Generator output breaker installation will perform satisfactorily on location. If the and alignment in the cubical, trip and "factory" tests discussed in 11.2 are done auxiliary relay calibration, and auxiliary on-site, they would follow this initial set-up. contact operation checks.

The tasks listed below illustrate how much is involved in a typical EDG set-up on-site: 10. Generator-Emergency (Class 1E) Bus automatic load sequencer or load

1. Remove shipping restraints and covers. sequence relay checks, calibration.

2. EDG base anchor setting followed by an 11. Engine Air start system, including:

acceptance alignment of the generator and engine, verified by crankshaft web

• Pressure integrity tests.

deflection checks.

• Relief valve tests.

• Air Compressor setting, alignment,

3. Engine internal checks and inspections, and motor phase rotation checks.

including:

• Air Compressor capacity; confirm time to fill the air receiver.

• Internal cleaning and flushing to

• Air pressure switch setpoint remove protective coatings.

calibrations, including verification of

• Bearing clearance (including thrust) compressor starting (low) and

• Cylinder bore and clearance/gap. stopping (high) pressure settings.

Rev 3/16 11-5 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing

12. Fuel Storage and transfer system,

• Off-skid coolant pump setting and including the following: alignment; motor phase rotation

• Pressure integrity tests (no leaks). verified (if applicable).

• Pressure relief valve tests.

• Coolant pump capacity verified.

• Fuel oil storage tank capacity and

• Coolant pump pressure switch fill level monitor calibration checks. setpoint calibrations.

• Fuel filter and strainer checks.

• Coolant system temperature switch

• Off-skid fuel oil transfer pump setpoint calibration.

setting, motor-pump alignment, and

• Coolant expansion tank level.

motor phase rotation checks.

• Coolant quality samples taken for

• Transfer pump capacity checks, analysis.

where the time to fill the fuel oil day tank is confirmed. 15. Ventilation system checks, including:

• Fuel Oil Day Tank Transfer Pump

• Fan alignment and motor phase level control switch calibration, rotation verified.

including verifying starting (low)

• Fan balancing.

and stopping (high) level settings.

• Fan flow and distribution verified.

• Verify fuel oil is per manufacturer's

• Ventilation system temperature specs for site ambient conditions. switch high and low calibration.

• Fuel Oil Day Tank Transfer Pump overfill ("high-high") level setpoint All the above pre-operational inspections, calibration (trip and alarm). checks, and tests are to verify that the EDG is properly assembled, anchored, and set

13. Lube oil system checks, including: up, the support systems and their controls

• Pressure integrity test. are properly configured and functioning, and

• Relief valve setpoint test. also that coolant, lube oil, and fuel oil

• Off-skid lube oil pump setting and compliant with the specs are present in the alignment, plus (if applicable) motor proper quantities. At this point the EDG is phase rotation check. ready for initial site acceptance tests and

• Lube oil pump capacity test. subsequent transfer to utility ownership.

• Oil filter and strainer checks.

• Lube oil system pressure switch 11.4 Site Acceptance Testing setpoint calibration.

• Lube oil system temperature switch Upon completion of system, subsystem, and setpoint calibration. component level checks and tests

• Lube oil sump level verified. associated with EDG initial set-up, the

• Lube oil quality samples taken for following on-site acceptance tests are analysis to verify spec compliance. conducted. These are full scope tests to demonstrate the capability of the unit to

14. Cooling system checks, including: perform its intended function, as installed.

• Pressure integrity tests. They are described in IEEE 387-1995

• Relief valve tests. Clause 7 and listed in Table 3.

Rev 3/16 11-6 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing Starting Test: Demonstrates the capability Whereas the Site Acceptance tests formed to attain and stabilize rated frequency and the basis for the utility to consider the EDG voltage within the limits and time specified. acceptable for its initial use, and to make final payment to the manufacturer, the Pre-Load Acceptance Test: Demonstrates the Operational tests are the first regulatory-capability to accept the individual loads that based site tests in which the licensee must make up the design load at that NPP, in the legally demonstrate and document EDG desired sequence and time duration, while performance. As "Pre-Operational" implies, maintaining voltage and frequency within they are a prerequisite to declaring the site acceptable limits. emergency power system operational.

Rated Load Test: Demonstrates ability to During the course of the pre-operational test carry the following loads without exceeding program, the EDG is started using all of the the manufacturer's design limits: (1) A load following methods:

equal to the continuous rating, maintained until engine temperatures reach equilibrium

• Manual Start pushbuttons, both from the plus one hour, followed by (2) The rated Control Room and at the EDG local short-time load, applied for two hours. control panel.

• Simulated Loss-of-Offsite Power event NOTE: The short-time load is typically 110% (LOOP), from the ESF bus "27" relays.

of the continuous rating and by definition

• Simulated Safety Injection Actuation can be applied 2 of each 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> (with the Signal (SIAS) from the Reactor other 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> at continuous load) without Protection System (RPS).

exceeding design limits or requiring less

• Combined LOOP and SAIS signals time between maintenance intervals.

Unlike Qualification, "Factory" and Site Electrical Tests: Verify characteristics of Acceptance testing, the Pre-Operational the generator, excitation system, voltage tests confirm proper functioning of all logic regulation system, engine governor, and the circuits and controls programming. Generic control and surveillance systems. Letter 96-01 addresses that requirement.

Subsystem Tests: Demonstrate control, NOTE: For all on-site testing, including Pre-protection, and surveillance systems are in Operational and Availability tests, follow accordance with requirements. manufacturer's recommendations for reducing engine wear:. Engine pre-lube, use 11.5 Pre-Operational EDG Testing of keep-warm system (if provided), and cool-down at reduced power following each test Following completion of site acceptance run. This issue will be discussed in Chapter testing, pre-operational tests are performed 13, as some licensees continue to subject to demonstrate starting and operational their EDGs to unnecessary stress and wear adequacy of the system. These are as listed by running rapid cold start tests with in Table 3 (reproduced herein) and immediate heavy step load. See Generic described in Clause 7.5 of IEEE 387-1995. Letters 84-15 and 94-01.

Rev 3/16 11-7 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing Before discussing Pre-Operational tests it NOTE: From this point forward, the Pre-may be helpful to describe the sequence of Operational tests become more demanding events that occur when offsite power is lost: in order to more closely simulate various Voltage sensing relays in the ESF bus trip emergency demand start scenarios and the related offsite power supply breaker and verify control systems are properly set up.

shed non-permanent bus electrical loads.

The EDG receives a start signal and loading Loss-of-Offsite Power (LOOP) Test: A is initiated when sensors report it has LOOP event is simulated as follows.

reached pre-determined speed and voltage.

The EDG output breaker will then close,

• Emergency buses are de-energized and picking up ESF bus permanent loads the loads are shed immediately. Auxiliary contacts in the

• EDG must start, attain required voltage-outbreak breakers also close, energizing frequency within acceptable limits and logic sequencers that control sequential time, energize the auto-connected shut-loading of the ESF bus by larger loads. down loads through load sequencer, and operate a minimum of 5 minutes.

Reliability Test: This is to demonstrate that an acceptable level of reliability has been Safety Injection Actuation Signal (SIAS) achieved to place the new EDGs into Test: This demonstrates that on SIAS the operation. It requires a minimum of 25 valid EDG starts from its standby condition upon start and load tests without failure, on each receipt of the auto-start signal, attains the installed EDG. required voltage and frequency within limits, and operates 5 minutes at no load.

Slow-Start Test: This is only to verify design frequency and voltage are attained. NOTE: During a plant emergency in which As the name implies, the unit is slowly Safety Injection cooling is required the plant brought up to speed, on a prescribed Main Turbine Generator will be off-line, due schedule that minimizes stress and wear. to loss of steam supply. The risk of grid destabilization and loss of the preferred Load-Run Test: This demonstrates basic (offsite) power supply is increased. The load-carrying capability, equivalent to 90- intent of this test is to confirm that upon an 100%, for not less than 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />. It may be SIAS signal the EDG will start to a running run by synchronizing the unit with the grid in standby mode, ready to accept ESF bus order to achieve the required load and PF. loads in the event a LOOP event occurs.

Again, loading and unloading are gradual, to That places the EDG in the best possible minimize stress and wear. status to immediately accept loads upon breaker closure and thereby minimize the Fast-Start Test: Each EDG unit will be disruption of SI reactor cooling.

started from standby conditions to verify that it reaches the required voltage and Combined SIAS and LOOP Test: This frequency within acceptable limits and time. combines the two tests immediately above, There is no loading with this test. and applies the same pass/fail criteria.

Rev 3/16 11-8 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing Largest-Load Rejection Test: When the Hot Restart Test: Demonstrates capability largest single load is shed the EDG must to restart immediately after a run at full load stay within acceptable voltage-frequency has stabilized engine temperatures at their limits and also not trip out on over-speed. full load values. (This can reveal one potential failure mode: Badly leaking fuel Design Load Rejection Test: The EDG injectors in a hot engine can create a vapor must not trip out on over-speed when it lock that is sufficient to prevent a restart.)

sheds a load equal to 90-100% of design loads. (There are no limits on voltage/ NOTE: As with previously described Slow frequency excursions, as this scenario Start and Fast Start tests, the Hot Restart presumes that all loads have been shed.) test does not involve applying load to the EDG. These tests just confirm that it can NOTE: Preventing over-speed trip of the achieve the running standby mode, ready to EDG is critical when all loads have been accept loads. In the running standby mode, lost. This minimizes EDG recovery time for control is as follows:

restoration of service to the related ESF bus electrical loads. Once the cause for full load

• EDG is at rated speed and frequency, rejection is isolated and corrected, the EDG with frequency control on the governor.

output breaker can quickly be re-closed to

• Generator is at rated voltage, controlled restore electrical service to the ESF bus. by the Automatic Voltage Regulator.

Although over-speed is an unacceptable Synchronizing Test: This demonstrates outcome of the load rejection test, it may ability to transfer emergency loads from the occur, in which case manual reset of the EDG to normal (offsite) power. It involves over-speed trip latch is required. Several synchronizing the EDG with the grid, then events have occurred as a consequence of transferring its load back to offsite power, failure to reset the over-speed trip latch. isolating the diesel-generator unit from the Immediate trips have occurred on startup. grid, and restoring it to standby status.

Delayed trips have occurred when the latch was not fully reset and vibrated loose during Protective Trip Bypass Test: This is to a run. (See IN 93-96 for details.) verify that protective trips are bypassed in emergency operation as designed. In most Endurance and Load Test: Demonstrates facilities, engine over-speed and generator capability to carry heavy loads for at least 24 differential current trip are not bypassed.

hours, of which 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> should be the short-time rating, and 22 hours2.546296e-4 days <br />0.00611 hours <br />3.637566e-5 weeks <br />8.371e-6 months <br /> is 90-100% of the Test Mode Override Test: Demonstrates continuous load rating. Voltage and that with the EDG operating in automatic frequency criteria must be met throughout. test mode while connected to its bus, a Presumably the loads may be applied in simulated SIAS overrides test mode by:

either order, as is explicitly permitted for basically the same EDG qualification test,

• Returning EDG to standby operation Load Capability, part (2). See 11.1.1 of this

• Automatically energizing emergency Chapter. loads from offsite power Rev 3/16 11-9 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing Independence Test: This demonstrates

• Safety Injection Actuation (SIAS) that simultaneously starting and running

• Combined SIAS and LOOP redundant EDG units does not result in any

• Largest-Load Rejection potential common failure modes that may be

• Design-Load Rejection undetectable in single-unit tests.

• Endurance and Load

• Hot Restart 11.6 Periodic Testing (Surveillance)

• Synchronizing

• Protective-Trip Bypass Periodic tests demonstrate the continued

• Test Mode Override capability of the EDGs to start and accept

• Independence (Verification) loads. They consist of availability, system operation, and independence verification Independence Verification Test: Following tests. See Table 3 from IEEE 387-1995, any modifications where the independence reproduced in this Chapter as Figure 11-1. of EDG units may have been affected, or at least every 10 years during plant shutdown 11.6.1 Availability Test: Each EDG unit or refueling outage, an independence shall be started and loaded at least once in verification test shall be performed. (This 31 days (slow start and load-run test, to subject will be included in the case history minimize engine stress and wear). Every discussions of Chapter 13.)

6th month, a combined Fast-Start, Load-Run test shall be done, simultaneously 11.7 Records for Each EDG Unit satisfying the Availability Test and that one semi-annual test requirement.

Extensive records shall be maintained and retrievable for each EDG unit to provide a NOTE: IEEE 387-1995, Clause 7.4.2.1, can be interpreted differently. However, RG 1.9 basis for analysis of its performance, to verify assumptions made, and to extend or (2.3.2.2) makes the intent clear, as above.

shorten equipment maintenance intervals and replacement schedules. The records 11.6.2 System Operation Tests: This is must include the following, as a minimum:

a series of tests to verify the ability of the EDG to perform its intended function under a) All start attempt, maintenance, repair, simulated accident conditions. These tests and out-of-service histories, cumulative shall be performed at shutdown/refueling operating and maintenance data, statistical outages (typically once every two years). analysis of EDG test results as well as actual demand runs.

The System Operation Tests listed in Table b) Critical failure mechanisms, human 3 have all been described previously in this errors, and common mode failures, with Chapter. They include the following: causes and corrective actions included.

• Slow-Start c) Test parameter data in accordance

• Load-Run with IEEE 387-1995, Table 4, which lists

• Fast-Start minimum engine operating data that must

• Loss-of-Offsite Power (LOOP) be maintained. (See Figure 11-2, herein.)

Rev 3/16 11-10 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing NOTE: All nuclear plants are required to these events can also impact the resulting have a program or measures in place to load, depending on which one occurs first address corrective actions, in accordance and the time between them. Furthermore, with 10 CFR 50, Appendix B, Criterion XVI. the definition of "short-time rating" is subject An effective corrective action provides the to interpretation, as engine manufacturers means for analyzing problems, finding root typically have several ratings higher than causes, developing corrective actions, and "continuous" (e.g., for running intervals of implementing solutions. 2000, 4, 2, and 0.5 hours5.787037e-5 days <br />0.00139 hours <br />8.267196e-6 weeks <br />1.9025e-6 months <br />). TI 2515 /176 requested extensive collection of data for 11.8 Concerns about the Adequacy of every EDG used for onsite standby power.

Licensee Periodic (Surveillance)

Testing Follow-up Report ML093370252 (Dec 2009) revealed NRC staff found that a DBE could The NRC issued Temporary Instruction (TI) load 46% (110 of the 239 EDGs evaluated) 2515 /176 in May 2008 to address concerns above their continuous or 2000 hour0.0231 days <br />0.556 hours <br />0.00331 weeks <br />7.61e-4 months <br /> rating!

about the adequacy of EDG surveillance Concerns were expressed about the impact testing. The catalyst was a finding that of extended operation after extreme weather endurance tests at Dresden NPS did not or natural disaster. (Parallel concerns were adequately verify EDG operability because subsequently raised by Fukushima.) See test loading did not bound predicted design- ML093370252 for additional information.

basis event (DBE) loads. The inconsistency was subsequently identified at other sites. 11.9 NRC Position on the Use of EDGs Further, NRR staff identified issues related for Peaking to test loading requirements, peak design-basis loading values / durations, and EDG Branch Technical Position ICSB-8 (PSB),

ratings, when reviewing license amendment "Use of Diesel Generator Sets for Peaking."

requests to correct endurance and margin testing acceptance criteria. Therefore, NRR The Instrument and Controls Systems staff issued the TI to assess the extent of Branch issued this technical position in 1981 these issues and to evaluate the adequacy concluding that "... the potential for common of EDG testing as prescribed in plant- mode failure modes should preclude specific TS and design bases. interconnection of the onsite and offsite power sources except for short periods for EDG loading is generally designed for a the purpose of load testing."

concurrent loss-of-offsite power and a loss of cooling accident (LOOP+LOCA). The Clearly, the use of EDGs for peaking is loading profile for a concurrent LOOP and strongly discouraged, if not prohibited. Both large-break (LB) LOCA is typically high. EDG systems should never be run in parallel However, at some sites the calculated load with the grid at the same time, as a power values were greater for a LOOP coincident line drop, plant substation fault, or transient with a small-break (SB) LOCA or a main could take out both standby power systems steam line break (MSLB) than they were for at the same time, leaving the station very the presumptive LOOP-LBLOCA. Timing of vulnerable to a subsequent LOOP.

Rev 3/16 11-11 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing 11.10 Observations on EDG Control Slight changes in the EDG governor circuit When in Parallel with Grid can result in EDG speed reference signal anomalies. These are typically due to things Monthly EDG Load-Run tests are usually causing changes in governor speed accomplished by synchronizing with the grid reference circuit resistance, such as circuit in order to facilitate achieving the required relay contacts and motor operating load. Achieving the proper load (90-100% potentiometers (MOPs).

of continuous), while avoiding potential problems related to running in parallel with

• If the EDG speed reference signal drops the grid can sometimes pose a challenge to in relation to grid frequency, the grid the EDG operator. takes KW load off the EDG.

11.10.1 Frequency-Load Control Issues

• If the EDG speed reference signal When Connected to the Grid increases in relation to grid frequency, the EDG picks up more KW load from the There can be several causes for EDG grid. Overload trip may occur.

frequency-load changes or swings while connected with the grid. The EDG cannot 11.10.2 Voltage-KVAR Control Issues have significant impact on the grid but can When Connected to the Grid certainly be affected by grid changes.

There can be several causes for EDG Slight grid frequency changes show up as voltage-KVAR changes or swings while KW load swings on the EDG. Therefore, connected with the grid. The primary one of the causes for EDG load swings while causes for EDG KVAR swings are:

connected to the grid are slight variations in grid frequency. Obviously, since the plant Slight grid voltage changes show up as KVA EDG operator has no direct ability to control (and therefore KVAR) load changes on the grid frequency, slight adjustments in EDG EDG. Since the plant EDG operator has no speed governor reference frequency are direct ability to control grid voltage, slight often required over the duration of the adjustments in EDG AVR reference voltage loaded run test. are often required over the duration of the loaded run test, in order to maintain the

• If grid frequency drops in relation to EDG required KVAR and the directly-related reference frequency, the EDG picks up power factor (pf).

more grid KW load. It could trip from overload when conducting rated load

• If grid voltage drops in relation to EDG and overload testing. reference voltage, the generator will take on more KVAR load from the grid. This

• If grid frequency increases in relation to will result in a decrease in the EDG EDG reference frequency, the grid takes power factor and an increase in KW load off the EDG. It could trip from generator output current. The generator reverse power if synchronized and overload trip relay is sensitive to current operating at low loads. whether from KW or KVAR.

Rev 3/16 11-12 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing

• If the grid voltage increases in relation to more KW load. The opposite is also true, EDG reference voltage, the grid relieves such that steadily reducing engine some of the KVAR load from the EDG. power, as if attempting to slow down, This will result in an increase or takes off KW load, eventually to where improvement in the EDG power factor. power flow reverses and the generator When operating near unity power factor, becomes a motor driven by the grid.

this may cause a generator loss of field trip (LOFT). 2. The generator "feels" KVA and, as a result, KVAR load. The KVAR load is Slight changes in the EDG AVR circuit increased by the voltage regulator resulting in EDG voltage reference signal attempting to increase the generator anomalies. These anomalies are typical output voltage (via the field). Of course, due to changes in the AVR voltage it can't raise grid voltage so that simply reference circuit resistance such as circuit results in the generator picking up more relay contacts and potentiometers (PDPs). KVAR load. The reverse is also true, such that if the voltage regulator tries to

• If the EDG voltage reference signal lower generator output voltage below drops in relation to grid voltage, the grid line voltage it will eventually get the field takes KVA (and, therefore, KVAR) load so low a loss-of-field trip occurs.

off the EDG. This will result in an increase or improvement in the EDG 3. To prevent problems, the EDG operator power factor, which may cause LOFT. will always connect to the grid with the generator synchronized (but rotating at a

• If the EDG voltage reference signal slightly higher frequency than the grid) increases in relation to grid voltage, the and with the generator output voltage EDG picks up more KVAR load from the slightly higher than grid voltage. The grid. This will result in an increase in subsequent disconnect will be made generator output current and could before getting too close to zero load. Of cause generator overload trips. course the EDG must be in "droop" mode whenever connected to the grid, to The operational impact of the above can be prevent inadvertent overload.

summarized by these three statements:

NOTE: Clause 4.5.2.2 of IEEE 387-1995

1. The engine "feels" KW load and is not requires that upon receipt of an emergency affected by KVAR load except to the start-diesel signal, the EDG's automatic extent that power factor impacts the control system shall provide automatic start-generator's efficiency. The KW load is up and adjustment of the speed (frequency) increased by the governor attempting to and voltage to a ready-to-load condition in increase RPM (generator frequency) by the isochronous mode. This is to prevent adding more fuel. Of course it can't, as reduced EDG performance in an emergency the engine-driven generator is locked in from being left in "droop" mode at the sync with the grid as long as connected conclusion of licensee's monthly to it, so the result is the EDG picks up surveillance testing.

Rev 3/16 11-13 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing 11.11 Typical EDG Surveillance Run KW load is gradually increased to 90-100%

of continuous for a period of not less than Following completion of pre-operational one (1) hour. The increase in load on the testing and licensing, EDG surveillance EDG is accomplished by adjusting the testing is conducted in accordance with governor speed reference potentiometer applicable regulatory documents and Plant (MOP) that will attempt to increase engine Technical Specifications, to assure system speed. However, since EDG speed is performance continues to be acceptable. limited and locked by grid frequency while operating in parallel, the increase in fuel EDG Starting: demand to the cylinders simply results in the EDG accepting more load from the grid.

The EDG is started, briefly warmed up, and Therefore, as the governor speed reference gradually raised to rated speed. MOP is adjusted:

EDG Loaded Run:

• The governor repositions fuel racks to uniformly increase fuel to all the NOTE: To protect the EDG while paralleled cylinders.

to the grid, the governor control is placed in

• However, EDG speed cannot increase the droop mode. In droop mode, with the as it is synchronized with the grid.

governor at a given speed reference point,

• Therefore, instead of an EDG speed an increase in load application to the EDG increase, load is uniformly increased on tends to allow a decrease in EDG speed, all EDG cylinders. In this manner, load thereby limiting new load acceptance. is gradually increased, often in steps, Therefore, with the governor in the droop until reaching nominal rated EDG load.

mode, a deliberate change in the governor

• Engine temperatures are monitored and speed reference point is required to the test continued for 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br /> min., or until increase or decrease EDG load. temperatures stabilize at full load.

• The EDG is loaded and unloaded in The EDG is synchronized and paralleled steps to minimize the stress and wear on with its associated ESF emergency bus, the unit.

which is already powered from the preferred

• Engine, generator, and support system offsite power supply (i.e. grid). To do this, parameters are closely monitored as the diesel speed is increased to the point where test progresses.

frequency is just slightly higher than the grid

• The generator load is monitored and (synchroscope rotating "slowly in the fast adjusted as necessary throughout the direction"). Typically, the generator output loaded run, while engine and generator breaker is closed while the synchroscope is operating parameters continue to be between 10 to 12 o'clock in one of its recorded as required by IEEE 387-1995 revolutions (unit paralleled). At this point the Clause 7.6 ("Records") and Table 4 diesel will be carrying some minimal load ("Test Parameters"), reproduced here as (part of it from the interconnecting 4KV bus, Figure 11-2. All such data are required plus some from the grid). to be "retrievable" for review.

Rev 3/16 11-14 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing EDG Unloading: Securing EDG Operation:

• The engine is allowed to operate for a Once EDG temperatures have stabilized, "cool down" interval, then shut down.

and the EDG has been at rated load at least 1 hour1.157407e-5 days <br />2.777778e-4 hours <br />1.653439e-6 weeks <br />3.805e-7 months <br />, the generator can be unloaded. The

• The EDG engine, generator, and support EDG is unloaded by adjusting the same systems are verified properly aligned for governor potentiometer in a manner that will emergency standby operation.

tend to decrease the engine reference speed. Generator load is thereby reduced Alert students will note no mention has been gradually to the minimum allowed in the made of KVAR load being ramped up and following manner: down with KW load. It is not necessary to do so. KVAR can be ignored until test KW KW load is then gradually reduced from 90 load is reached. Then the voltage regulator to 100 percent to no less than10 percent of is used to adjust KVAR load to the value its rated load. (This compensates for meter desired. When the load run is completed and meter reading errors and minor KVAR load is brought down first, to keep the fluctuations in frequency in order to avoid Power Factor within normal bounds. Then reverse power trips.) The decrease in load KW load is ramped down before disconnect.

on the EDG is accomplished by adjustment of the governor speed reference 11.12 Observations Pertaining to EDG potentiometer (MOP) such that it will attempt Selection and Operation to decrease engine speed. However, since EDG speed is limited and locked by grid The general EDG criteria applied include:

frequency while continuing to operate in parallel the decrease in fuel demand to the "continuous load rating (the 8760 hour0.101 days <br />2.433 hours <br />0.0145 weeks <br />0.00333 months <br /> cylinders allows the EDG to reject most of its rating, per IEEE-387) equal to the sum of the load back to the grid. Therefore, as the conservatively estimated loads (nameplate) governor speed reference MOP is adjusted: needed to be powered by that unit at any one time plus a 10 to 15 percent margin."

• The governor repositions fuel racks to "at no time during the loading sequence uniformly decrease fuel to all the should the frequency decrease to less than cylinders; 95% of the nominal nor voltage decrease to

• However, the EDG speed cannot less than 75% of nominal."

decrease, as the grid will keep the generator in lock step with it, whether "frequency should be restored to within generating or being driven as a motor. 2% of the nominal (60 Hz) in less than 60%

• Therefore, EDG RPM cannot decrease, of each load-sequence interval for stepload and load is uniformly decreased on all increase and less than 80% of each load-cylinders, often in steps, until the EDG sequence interval for disconnection of single has been unloaded to the desired KW largest load. Voltage should be restored to and KVAR values for disconnection from within 10% of nominal within 60% of each the grid (typically to about 10% of test). load-sequence (reduction) time interval."

Rev 3/16 11-15 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing "during recovery from transients caused performance of other equipment already by the disconnection of the largest single operating. The following scenario may load, the speed of the diesel generator unit demonstrate what could happen during such should not exceed the nominal speed plus conditions at a plant utilizing a pressurized 75% of the difference between nominal water reactor.

speed and the over-speed trip setpoint, or 115% of nominal, whichever is lower. An EDG is started in response to a Safety Further, the transient following the complete Injection (SI) with Loss of Offsite Power loss of load should not cause the speed of (LOOP) signal and the output breaker the unit to attain the speed of the overspeed closes within 10 seconds. The EDG accepts trip setpoint." primary motor loads in the following sequence:

Following are several simplified examples that may help demonstrate the relationship

• Charging Pump rated @ 450 KW.

between load application and the EDG

• High Head Safety Injection Pump rated voltage and frequency. @ 300 KW.

Continuous Load Example: If a plant

• Low Head Safety Injection (RHR) Pump identifies in the design stage that the rated @ 300 KW.

required loads on the emergency onsite

• Component Cooling Water Pump rated alternating current (AC) power supply will be @ 400 KW.

4500 KW, the minimum specified diesel

• Essential Cooling Water Pump rated @

generator continuous load rating should be 350 KW.

5000 KW (or 4950 KW, rounded up for

• Motor Driven Auxiliary Feedwater Pump conservatism). This will accommodate for rated @ 450 KW.

slight design calculation errors without exceeding diesel generator continuous

• Containment Spray Pump, @ 450 KW.

rated capacity. The NPP's approaching or perhaps even exceeding their initial EDG At the point when it becomes necessary to electrical load ratings are typically earlier bring the Containment Spray (CS) Pump on design and construction plants that were line, a substantial portion of the EDGs rated adversely impacted by TMI backfits that load is already applied. This is also a increased the required loads. significant load in itself. If the diesel generator is undersized, this can cause an Load Sequencing Example: Safety system undesirable transient response as the pump motor loads at nuclear power plants are motor breaker (motor contactor) is closed, primarily large induction motors. This type connecting the pump motor to the bus being of motor, with full voltage applied, draws a supplied by the EDG. A nominal load starting current five to eight times its rated sequence interval (point of load application operating current. The generator and diesel to point of meeting acceptance criteria) is engine selected must have sufficient about 3 seconds. The following is a basic capacity to support the startup of such overview of what physically occurs in equipment without adversely affecting the response to this transient.

Rev 3/16 11-16 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing Discussion of Voltage Transient, for the generator load application). From steady described load application: As the motor state analysis, generator voltage will be contactors close, the 4KV Bus voltage restored to the same nominal 4160 volts.

decreases (dips). This primarily occurs due However, there will be a new higher current to the sudden motor starting inrush current and KVA output. Generators are rated in (as much as 5 to 8 times higher than nominal KVA, and the addition of the Containment running current) required to accelerate the Spray Pump load will increase the KVA 450KW CS Pump motor, which is likely output of the generator closer to its rated already under system load (system KVA output. This increase in generator load demand). As a result, diesel generator is directly applied to the engine. The output voltage also drops. The EDG voltage increased load on the engine tends to cause regulator senses the voltage drop and the it to slow down (decrease in RPM). The voltage regulator acts to restore the desired engine governor senses this transient generator output voltage (most often 4160 reduction in RPM and acts to move fuel volts) in respond to the transient. This racks to increase the fuel to engine cylinders transient response characteristic of the in order to restore engine RPM to what is generator and regulator is critical in the required for 60 Hz generator output. As selection process. As noted earlier, noted earlier, RG 1.9 requires that:

Regulatory Guide 1.9 requires that:

• The frequency not drop below 95% of

• Voltage should not drop below 75% of nominal (57 Hz).

nominal (3120 volts, if 4160 nominal).

• Generator output should be capable of

• Engine and governor response should restoring voltage to within 90% of be capable of restoring frequency to nominal (in this case, 3744 volts) within within 2% of nominal (58.8) within 60%

60% of each load sequence interval (i.e., of each stepload increase sequence 1.8 seconds for a nominal 3 seconds interval (1.8 seconds for a 3s interval).

interval).

If the diesel generator output, based on NOTE: For analysis of EDG frequency, generator or engine capabilities or both, is remember that the generator frequency is a selected too close to system demand dependent variable of engine speed and, requirements, the resulting transient therefore, whenever engine speed changes response characteristics will likely be the generator frequency is also changed in unacceptable. This becomes increasingly the same proportion. evident when large loads are placed on the unit already carrying a substantial portion of Frequency Transient Overview for the its rated load.

described load application: At the same time that the generator is reacting to restore Load Disconnection (reject or loss) voltage, the engine senses the transient in Example: Both voltage and frequency will the form of decreasing unit speed (RPM) tend to increase on a loss of load. The caused by direct generator feedback (i.e. following scenario may demonstrate what Rev 3/16 11-17 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing could happen during the trip of the As noted previously, Regulatory Guide 1.9 Centrifugal Charging Pump or the Motor requires that: Frequency should not exceed Driven Auxiliary Feedwater Pump at the 75% of the difference between nominal example pressurized water reactor plant. engine speed and the over-speed trip setpoint, or 115% of nominal, whichever is Voltage Transient Overview (for loss of lower. (At 115% speed the generator load): As the motor contactors open, the frequency would be 115% of 60Hz, resulting 4KV Bus voltage tends to increase due to in 69Hz output.) Engine and governor the sudden reduction in current required to response should be capable of restoring operate the 450 KW pump motor. As a frequency to within 2% of nominal (60 +/- 1.2 result, generator output terminal voltage Hz) within 80% of the single largest load also increases. The voltage regulator disconnection sequence interval (2.4 senses the voltage increase and acts to seconds when the nominal load disconnect decrease the generator voltage to the interval is 3 seconds).

desired value (nominally 4160 volts) in response to this transient. As noted earlier, EDG Governor, Speed and Frequency:

RG 1.9 requires that the Generator must be There are two modes of governor operation capable of restoring voltage to within 90% of applicable to most EDG applications at nominal (typically 4576 volts) within 60% of nuclear power plants. These are referred to each load sequence interval (1.8 seconds as "isochronous" (constant speed) and for a nominal 3 seconds interval). "droop" (speed reduction as load increase).

Frequency Transient Overview (for loss Governor Control Under Emergency of load): If a sudden loss of a large load Operation: An EDG operating in response occurs (e.g. breaker trip to one of the 450 to a design basis event will be connected to KW motor, single largest loads, applied), an isolated 4KV Bus (i.e. isolated from the this loss of load will cause EDG speed offsite grid). In this condition the desirable (RPM) to rapidly increase. This speed EDG governor speed control is referred to increase occurs since fuel racks are set to as isochronous (constant speed control). In provide more fuel (meaning a higher heat, isochronous speed control, the governor will firing pressure, and power output) than attempt to maintain engine speed constant required to maintain rated speed for the new regardless of the load applied, so the (lower) load. In this case, the engine generator will provide approximately 60Hz governor will sense the speed increase and power.

rapidly respond to move fuel racks to decrease fuel delivery to the engine Governor Control Under Normal Test cylinders and restore engine RPM to the Operation: Frequently, for purposes of desired range (equivalent to 60 Hz). Since testing and restoration of power to the grid, the EDG has no braking system, speed the EDG must be paralleled with the grid. In reduction is partly dependent on the this condition, the desirable governor speed remaining load and the unit's inertial (WR2) control characteristic is called the droop characteristics. mode of operation. The generator on the Rev 3/16 11-18 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing system grid with the highest frequency some ESF loads can have more limiting (speed) will attempt to be the lead unit (and frequency requirements, meaning they are hence, hog system load). In the case of a less tolerant of frequency changes based on diesel generator having a nominal output of their design performance criteria.

perhaps 5000 KW = 5 Mega Watts (MW),

synchronized to a grid with a load demand For example, if an accident analysis expects in the thousands of MW, trying to be the lead an ESF pump to have a minimum design unit could be catastrophic. Therefore, basis flow corresponding to a speed greater whenever running in parallel with the grid, than the minimum EDG frequency allowed the governor must be in the droop mode so (frequency and engine speed being directly that its speed is reduced slightly as the load related), that pumps safety margin is is increased. In droop mode the governor eroded. Therefore, the licensee will analyze limits the load on the EDG and how much it for adverse ESF load impacts associated can increase in response to grid transients. with EDG frequency within the allowed governor speed control band. Occasionally As an example, most governors are set for this design basis analysis of ESF loads can a speed droop between 2.5% and 5% when result in establishing more stringent going from no-load to full-load operation. frequency (EDG governor speed control)

The former results in 61.5 Hz at no load and band limits.

the latter setting results in 63Hz at no load.

For any droop setting the frequency at full System Load Power Factor In Generator load operation is a nominal 60 Hz. When in Selection Considerations: Generators are parallel with the grid, the governor's droop selected and constructed in accordance with circuit is enabled and the speed regulation National Electrical Manufacturers circuit (usually through a motor operated Association (NEMA) Standards, primarily:

potentiometer or MOP) is used to change

• MG-1 the "speed reference point" thereby

• MG-2 enabling EDG load control.

Load power factor is one of the significant Technical Specification Limits for considerations given in generator selection.

Frequency and Voltage: Typical EDG Unless otherwise specified, system power Technical Specifications require the factor is assumed to be 0.8 ("lagging") for generator regulator be capable of generator selection. Since power factor is maintaining output voltage within 10% of a actually a characteristic of the system load nominal 4160 volts (4160 +/- 420 volts) and and not the generator it is important that the the governor to maintain engine speed system load have a power factor of 0.8 (frequency) within 2% of 60 Hz (60 +/- 1.2 Hz) lagging, or better. Power factor can be at steady state. These minimum EDG viewed as the byproduct of a parasitic performance criteria are aimed at system load (KVAR, or system reactive maintaining voltage and frequency within load, sometimes called imaginary power).

limits acceptable to most Engineered Safety It must be supplied by the generator but Features (ESF) loads. However, note that does no work, unlike KW (real power).

Rev 3/16 11-19 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing As previously noted, generators are typically rated in KVA with this associated limiting load power factor (pf) applied to determine the theoretical true or real power available to operate loads. In many cases, since load power factor is better than 0.8 (lagging), available true power is higher than rated. An expected worst case load power factor is specified or assumed in order to establish the generator characteristic design point that will determine its system transient and full load response capabilities.

As discussed in an earlier chapter, power factor can be expressed several different ways and one common method of expression is true power (KW) over apparent power (KVA) or (PF = KW /KVA).

Another way to define power factor is the amount by which the generator current lags the output voltage. Regardless, most emergency diesel generators are designed to accommodate a 0.8 lagging system power factor at the rated KW output. For example, a generator required to supply 5000 KW to an isolated 4KV bus operating

@ a 0.8 power factor (PF = 0.8), requires a generator KVA rating of 5000/0.8, or 6250 KVA.

NOTE: Most plant 4KV systems actually have power factors of 0.85 or better.

Rev 3/16 11-20 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing Figure 11-1 IEEE 387-1995, Table 3, Site Testing of EDGs Rev 3/16 11-21 of 22 USNRC HRTD

Emergency Diesel Generator Qualification, Site Acceptance, and Surveillance Testing Figure 11-2 IEEE 387-1995, Table 4, Test Parameters (Required Data)

Rev 3/16 11-22 of 22 USNRC HRTD