Regulatory Guide 1.9

Selection, Design, and Qualification of Diesel-Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants

ML13350A381
Person / Time
Issue date:	11/30/1978
From:	NRC/OSD
To:
References
RG-1.009, Rev. 1
Download: ML13350A381 (3)

Revision 1 November 1978 U.S. NUCLEAR REGULATORY

COMMISSION

k REGULATORY

GUIDE OFFICE OF STANDARDS

DEVELOPMENT

REGULATORY

GUIDE 1.9 SELECTION, DESIGN, AND QUALIFICATION

OF DIESEL-GENERATOR

UNITS USED AS ONSITE ELECTRIC POWER SYSTEMS AT NUCLEAR POWER PLANTS

B. DISCUSSION

General Design Criterion 17, "Electric Power A diesel-generator unit selected for use in an Systems," of Appendix A, "General Design onsite electric power system should have the Criteria for Nuclear Power Plants," to 10 CFR capability to (1) start and acceate a number Part 50, "Domestic Licensing of Production and of large motor loads in rapid ar sion and be Utilization Facilities," includes a requirement able to sustain the loss ok an o%1._y part of that the onsite electric power system have such loads and maintain an, Irequency sufficient capacity and capability to ensure within acceptable limit " supply power that (1) specified acceptable fuel design limits continuously to the i V~eded to main-and design conditions of the reactor coolant tain the plant in a .*2e c 4itioA if an extended pressure boundary are not exceeded as a loss of offsite po A~r o urý b'result of anticipated operational occurrences A*and (2) the core is cooled and containment in- IEEE Std -197 ;,,; E Standard Criteria tegrity and other vital functions are maintained for Diesel-G k*tor mits Applied as Standby in the event of postulated accidents.

Power " K Nuclear Power Generating Stations 4ceea'kes principal design criteria Criterion III, "Design Control," of Appen- an a testing requirements that, if dix B, "Quality Assurance Criteria for Nuclear foI , help ensure that selected diesel-Power Plants and Fuel Reprocessing Plants," to .genrhrat" Units meet their performance and 10 CFR Part 50 includes a requirement that ' a IEEE Std 387-1977 was measures be provided for verifying or checking 'f; ed by Working Group 4.2C of the the adequacy of design by design reviews, J%$. cl r Power Engineering Committee (NPEC)the use of alternative or simplified calculati al 0 ot .he Institute of Electrical and Electronics methods, or by the performance of a suit".e Engineers, Inc. (IEEE), approved by NPEC, testing program. , and subsequently approved by the -IEEE Stan--" dards Board on September

9, 1976. IEEE Std Diesel-generator units have been wiely ud 387-1977 is supplementary to IEEE Std 308-as the power source for the onsi V le ic 1974, "IEEE Standard.

Criteria for Class IE power systems. This regulatory gfiae -Power Systems and Nuclear Power Generating scribes a method acceptable to the NRC staff Stations,"'

and specifically amplifies paragraph for complying with the a mission's require- 5.2.4, "Standby Power Supplies," of that doc-ments that diesel-gene units intended for ument with respect to'the application of diesel-use as onsite power r j nuclear power generator units. IEEE Std 308-1974 is en-plants be selected with ic capacity and dorsed, with certain exceptions, by Regulatory be qualified for v Guide 1.32, "Criteria for Safety-Related Electric Power Systems for Nuclear Power wThe substantial her of ges in this revision has made Plants. " it impractical to the c ges es in the margin.'Copies e the Institute of Electrical and Electronics In .. n ited Engineering Center, 345 East 47th Street, ork, New York 10017.A knowledge of the characteristics of each load is essential in establishing the bases for USNRC REGULATORY

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the selection of a diesel-generator unit that is able to accept large loads in rapid succession.

The majority of the emergency loads are large induction motors. This type of motor draws, at full voltage, a starting current five to ten times its rated load current. The sudden large increases in current drawn from the diesel generator resulting from the startup of induc-tion motors can result in substantial voltage reductions.

The lower voltage could prevent a motor from starting, i.e. , accelerating its load to rated speed in the required time, or cause a running motor to coast down or stall. Other loads might be lost if their contactors drop out. Recovery from the transient caused by starting large motors or from the loss of a large load could cause diesel engine overspeed which, if excessive, might result in a trip of the engine. These same consequences can also result from the cumulative effect of a sequence of more moderate transients if the system is not permitted to recover sufficiently between suc-cessive steps in a loading sequence.Generally it has been industry practice to specify a maximum voltage reduction of 10 to 15 percent when starting large motors from large-capacity power systems and a voltage reduction of 20 to 30 percent when starting these motors from limited-capacity power sources such as diesel-generator units. Large induction motors can achieve rated speed in less than 5 seconds when powered from adequately sized diesel-generator units that are capable of restoring the voltage to 90 percent of nominal in about 1 second.Protection of the diesel-generator unit from excessive overspeed, which can result from a loss of load, is afforded by the immediate oper-ation of a diesel-generator unit trip, usually set at 115 percent of nominal speed. In addi-tion, the generator differential trip must oper-ate immediately in order to prevent substantial damage to the generator.

There are other pro-tective trips provided to protect the diesel-generator units from possible damage or degra-dation. However, these trips could interfere with the successful functioning of the unit when it is most needed, i.e. , during accident conditions.

Experience has shown that there have been numerous occasions when these trips have needlessly shut down diesel-generator units because of spurious operation of a trip circuit. Consequently, it is important that measures be taken to ensure that spurious ac-tuation of these other protective trips does not prevent the diesel-generator unit from performing its function.The uncertainties inherent in estimates of safety loads at the construction permit stage of design are sometimes of such magnitude that it is prudent to provide a substantial margin in selecting the load capabilities of the diesel-generator unit. This margin can be provided by estimating the loads conservatively and selecting the continuous rating of the diesel-generator unit so that it exceeds the sum of the loads needed at any one time. A more accu-rate estimate of safety loads is possihle duringl the operating license stage of review because detailed designs have been completed and preoperational test data are available.

This permits the consideration of a somewhat less conservative approach, such as operation with safety loads within the short-time rating of the diesel-generator unit.C. REGULATORY

POSITION Conformance with the requirements of IEEE Std 387-1977, "IEEE Standard Criteria for Diesel-Generator Units Applied as Standby Power Supplies for Nuclear Power Generating Stations," dated June 17, 1977, is acceptable for meeting the requirements of the principal design criteria and qualification testing of diesel-generator units used as onsite electric.power systems for nuclear power plants subject to the following:

1. When the characteristics of loads are not accurately known, such as during the con-struction permit stage of design, each diesel-generator unit of an onsite power supply system should be selected to have a continuous load rating (as defined in Section 3.7.1 of IEEE Std 387-1977)

equal to or greater than the sum of the conservatively estimated loads needed to be powered by that unit at any one time. In the absence of fully substantiated performance characteristics for mechanical equipment such as pumps, the electric motor drive ratings should be calculated using conservative esti-mates of these characteristics, e.g., pump runout conditions and motor efficiencies of 90%or less.2. At the operating license stage of review, the predicted loads should not exceed the short-time rating (as defined in Section 3.7.2 of IEEE Std 387-1977)

of the diesel-generator unit.3. During preoperational testing, the pre-dicted loads should be verified by tests.4. In Section 5.1.1, "General," of IEEE Std 387-1977, the requirements of IEEE Std 308-1974 should be used subject to the regulatory position of Regulatory Guide 1.32.5. Section 5.1.2, "Mechanical and Electrical Capabilities," of IEEE Std 387-1977 should be supplemented with the following: "Each diesel-generator unit should be capa-ble of starting and 'accelerating to rated speed, in the required sequence, all the needed engineered safety feature and emer-gency shutdown loads. At no time during the loading sequence should the frequency and voltage decrease to less than 95 percent of nominal and 75 percent of nominal, respec-tively"b Frequency should be restored to 1.9-2

• within 2 percent of nominal, and voltage should be restored to within 10 percent of nominal within 60 percent of each load-sequence time interval. (A greater percent-age of the time interval may be used if it can be justified by analysis.

However, the load-sequence time interval should include suffi-cient margin to account for the accuracy and repeatability of the load-sequence timer.)During recovery from transients caused by step load increases or resulting from the disconnection of the largest single load, the speed of the diesel-generator unit should not exceed the nominal speed plus 75 percent of the difference between nominal speed and the overspeed trip setpoint or 115 *percent of nominal, whichever is lowei. Further, the transient following the complete loss of load should not cause the speed of the unit to attain the overspeed trip setpoint." 6. In Section 5.4, "Qualification," of IEEE Std 387-1977, the qualification testing require-ments of IEEE Std 323-1974, "IEEE Standard for Qualifying Class IE Equipment for Nuclear Power Generating Stations,"'

should be used subject to the regulatory of Regulatory Guide 1.89, "Qualification of C!ass IE Equip-ment for Nuclear Power Plants." 7. Section 5.5, "Design and Application Con-siderations," of IEEE Std 387-1977 should be supplemented with the following: "Diesel-generator units should be designed to be testable during operation of the nuclear power plant as well as while the plant is shut down. The design should include provisions so that the testing of the units will simulate the parameters of operation (outlined in Regulatory Guide 1.108, "Periodic Testing of Diesel-Generator Units Used as Onsite Electric Power Systems at Nuclear Power Plants") that would be expected if actual demand were to be placed on the system."Testability should be considered in the selection and location of instrumentation sen-sors and critical components (e.g., gover-nor, starting system components), and the overall design should include status indica-tion and alarm features.

Instrumentation sensors should be readily accessible and designed so that their inspection and calibra-tion can be verified in place." 8. Section 5.6.2.2, "Automatic Control," of IEEE Std 387-1977 should be supplemented with ,the following:

(3) "With the exception of the engine over-speed trip and the generator differential trip, all diesel-generator protective trips should be either (1) implemented with two or more independent measurements for each trip parameter with coincident logic provisions for trip actuation or (2)automatically bypassed during accident conditions.

The design of the bypass circuitry should satisfy the requirements of IEEE Std 279-1971 at the diesel-generator system level and should include the capability for (I) testing the status and operability of the bypass circuits, (2) alarming in the control room abnormal values of all bypass param-eters, and (3) manually resetting of the trip bypass function. (Capability for automatic reset is not acceptable.)" 9. Section 5.6.3. 1, "Surveillance Systems," or IEEE Std 387-1977 should be supplemented with the following: "In order to facilitate trouble diagnosis, the surveillance system should indicate which of the diesel-generator protective trips is acti-vated first." 10. In Section 6.3, "Type Qualification Test-ing Procedures and Methods," of IEEE Std 387-1977, the requirements of IEEE Std 344-1975,"Recommended Practices for Seismic Qualifica- tion of Class 1E Equipment for Nuclear Power Generating Stations," for seismic analysis or seismic testing by equipment manufacturers should be used subject to the regulatory posi-tion of Regulatory Guide 1.100, "Seismic Quali-fication of Electric Equipment for Nuclear Power Plants." 11. The option indicated by "may" in Sec-tion 6.3.2(5)(c)

of IEEE Std 387-1977 should be treated as a requirement.

12. Section 6.5, "Site Acceptance Testing," and Section 6.6, "Periodic Testing," of IEEE Std 387-1977 should be supplemented by Regu-latory Guide 1.108.13. Section 4, "Reference Standards," of IEEE Std 387-1977 lists additional applicable IEEE standards.

The specific applicability or acceptability of these referenced standards has been or will be covered separately in other regulatory guides, where appropriate.

D. IMPLEMENTATION

This proposed guide has been released to encourage public participation in its develop-ment. Except in those cases in which an appli-cant proposes an acceptable alternative method for complying with specified portions of the Commission's regulations, the method to be described in the active guide reflecting public comments will be used in the evaluation of applications for construction permits docketed after the implementation date to be specified in the active guide. This implementation date will in no case be earlier than July 1979.If an .applicant wishes to use this draft guide in an application docketed prior to the imple-mentation date, the pertinent portions of the application will be evaluated on the basis of this draft guide.1.9-3