nema-sm-24-1991-r2002

NEMA Standards Publication No. SM 24-1991 (R1997, R2002)

Land-Based Steam Turbine Generator Sets 0-33,000 kW

Published by:

National Electrical Manufacturers Association 1300 North 17th Street, Suite 1847 Rosslyn, VA 22209

O Copyright 2002 by the National Electrical Manufacturers Association. All rights including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions.

Copyright National Electrical Manufacturers Association Provided by IHS under license with NEMANo reproduction or networking permitted without license from IHS

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NOTICE AND DISCLAIMER

The information in this publication was considered technically sound by the consensus of persons engaged in the development and approval of the document at the time it was developed. Consensus does not necessarily mean that there is unanimous agreement among every person participating in the development of this document.

The National Electrical Manufacturers Association (NEMA) standards and guideline publications, of which the document contained herein is one, are developed through a voluntary consensus standards development process. This process brings together volunteers andlor seeks out the views of persons who have an interest in the topic covered by this publication. While NEMA administers the process and establishes rules to promote fairness in the development of consensus, it does not write the document and it does not independently test, evaluate, or verify the accuracy or completeness of any information or the soundness of any judgments contained in its standards and guideline publications.

NEMA disclaims liability for any personal injury, property, or other damages of any nature whatsoever, whether special, indirect, consequential, or compensatory, directly or indirectly resulting from the publication, use of, application, or reliance on this document. NEMA disclaims and makes no guaranty or warranty, express or implied, as to the accuracy or completeness of any information published herein, and disclaims and makes no warranty that the information in this document will fulfill any of your particular purposes or needs. NEMA does not undertake to guarantee the performance of any individual manufacturer or sellers products or services by virtue of this standard or guide.

In publishing and making this document available, NEMA is not undertaking to render professional or other services for or on behalf of any person or entity, nor is NEMA undertaking to perform any duty owed by any person or entity to someone else. Anyone using this document should rely on his or her own independent judgment or, as appropriate, seek the advice of a competent professional in determining the exercise of reasonable care in any given circumstances. Information and other standards on the topic covered by this publication may be available from other sources, which the user may wish to consult for additional views or information not covered by this publication.

NEMA has no power, nor does it undertake to police or enforce compliance with the contents of this document. NEMA does not certify, test, or inspect products, designs, or installations for safety or health purposes. Any certification or other statement of compliance with any health or safety-related information in this document shall not be attributable to NEMA and is solely the responsibility of the certifier or maker of the statement.


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STD-NEMA SM 24-ENGL 199L b470247 0527195 732 m

-

NATIONAL ELECTRICAL MANUFACT


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NEMA Standards Publication No. SM 24-1991 (R1997)

Land Based Steam Turbine Generator Sets O - 33,000 kW

Published by:

National Electrical Manufacturers Association 1300 North 17th Street, Suite 1847 Rosslyn, VA 22209

O Copyright 1997 by the National Electrical Manufacturers Association. All rights including translation into other languages, reserved under the Universal Copyright Convention, the Berne Convention for the Protection of Literary and Artistic Works, and the International and Pan American Copyright Conventions.


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STDmNEMA SM 24-ENGL 1991 b470247 0521397 505

TABLE OF CONTENTS

p y c POREWORD . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . i SCOPE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . U

W i o n 1 REFERENCED STANDARDS & DEFINITIONS . . . . . . . . . . . . . . . . . . . . . . 1 keferenced standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1 Defitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 2

W l o n 2 CONSTRUCiON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types of Steam Turbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classified by Exhaust conditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classified by Number of Stages and Conml Valves .................... ClassXedbyProcessNeeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Steam Turbine Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Minecasing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steam Chest (Governor Valve Body) . . . . . . . . . . . . . . . . . . . . . . . . . . . . SteamRing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nozzles . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stationary Reversing Blades . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stationary Reversing Chambers . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Diaphragm . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stage. Twihe . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . shaftseals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BearingHousing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Bearings . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . RotorAssembly . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . wheels pisCs) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Blades (Buckets) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shroud . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hand Valve(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Protective Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Controlling Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Extemal Conml Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . WarningDeVice . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sentinel Warning Valve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Soleplate(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Baseplate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

FeaturesandAccessOnes . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Basic Features and Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Optional Features and Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Controlled Exuaction and Controlled Induction Turbines Noncontrolled Extraction Turbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Nonconuolled induction Turbines . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Turbine Generator Rating . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Power . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . FrequencyandSpxd . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Voltage . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SteamConditions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Units of Measurement for Absolute Pressure and Gauge Pressure . . . . . . . . . . . .

ThermodynamicTerms . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . .

7 7 7 7 7 7 7 7 7 8 8 8 8 8 8 8 8 9 9 9 9 9 9 9 9 9 9 9 9 10 10 10 10 10 11 12 12 12 12 12 12 13 15 15


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Section 2 SteamandHeat Rates . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

TurbineConnectio ns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Output shaft Extensions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SteamConnections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Auxiliary Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NonpressureTypeLubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. Pressure-?Lpe Lubrication . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Combination of Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Provisions for the Envhnment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Enclosure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exposure to Natural Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Exposure to Abnormal Atmospheric Conditions

General Mechanical Requkments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure and Tempemme Ranges . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Vibration . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . criticalspeeds . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . NameplateData . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shortcircuit . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

GearConstniction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Types . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ServiceFactor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Types of Generators . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classified by Rotor Construction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classified By Exciration Means . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Classified by Enclosure and Cooling Means

Generator Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . insulation System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PowerTerminals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

General Electrical Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Motor Starting Capabilities . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Maximum Momentary Overload . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Telephone influence Factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Efficiency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generator Constants . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Phasesequence . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . .

pqr

15 16 16 18 18 18 18 18 19 19 19 19 20 20 20 20 u) 20 23 23 23 23 23 23 23 24 25 25 27 27 27 28 28 28 28 28

Section 3 CONTROLS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Governing System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SpeedGovemor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Multivariable Governor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Conml Mechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Governor Controlled Vaive(s) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Servomotor System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . External Control Devices . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Speed Changer Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Valve Actuating Type . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Speed Changer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Speed Governing System Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SpeedRange . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . MaximumS peedRise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Speedvariation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

31 31 31 31 31 31 31 31 31 31 31 31 32 32 32


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Section 3 Speed Regdation. Steady State . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

SteamPmsureControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure Regulating System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . PressureRegulator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ControlMechanism . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure controlled valves . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressurechanger . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steady-Staie Pressure Regulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Stability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Pressure Control hrformance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Compensated Control System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Electronic Governing System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BasicFeatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Automatic Start Controls . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turbine Generator Controis . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Synchronous Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Frequency Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Voltage Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . LoadControl . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

induction Generator . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generation System Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generator Voltage Control . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

BasicFeatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Generator Conml Panel and Switchgear . . . . . . . . . . . . . . . . . . . . . . . . . . . Low Voltage Switchgear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . High Voltage Switchgear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generator and Switchgear Accessories . . . . . . . . . . . . . . . . . . . . . . . . . . .

General Requirements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Section 4 PROTECTION . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . BasicFeatures . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

ManuaiTnp . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overspeed Trip System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Overspeed Sensing Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tripspeed . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Tripvalve . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Combined Trip and Throule Valve Overspeed Trip System Seing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Overcurrent . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Section 5 FACTORY TESTING . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Turbine . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

HydroTest . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . No Load Running Test . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Gear . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Gener;itor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Combined Test (Optional) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

32 34 34 34 34 34 35 35 35 35 36 36 36 36 37 37 37 37 37 37 37 37 39 39 39 39 39 40 40 40 45

47 47 47 47 47 47 47 47 47 47

49 49 49 49 49 49 50


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STD-NEMA SM 24-ENGL L991 b1)30247 0527200 2 T m

Section 6 SOUND PRESSURE LEVELS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . General . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SoundPressureLevels . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sound Pressure Levei Measurement Rocedure Correction for Background Noise . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . SoundResolution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Instruments . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Sound Attentuation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Section 7 PREPARATION FOR SHIPMENT AND STORAGE . . . . . . . . . . . . . . . . . . . . Shipping Reparation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Shipment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Receipt and Storage of Equipment

. . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section 8 INSTALLATiON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Supervision of Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Installation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Foundation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steam Inlet and Exhaust Piping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Cleaning of Turbine Steam Piping

Steam Piping Systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . The Piping Problem as Applied to Turbines Farces Due to Steam Pressure . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Forces Due to Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Forces Due to Dead Weight . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Allowable Forces and Moments on Steam Tuhines

DrainPiping . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Leak-offs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Full-Flow Relief Device . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Coupling Alignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Grouting . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Hushing Oil System . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Generatorieads . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . . . . . .

. . . . . . . . . . . . . . . . . . . .

Sample Problems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Section 9 OPERATION AND MAINTENANCE . . . . . . . . . . . . . . . . . . . . . . . . . . . .

introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Operation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Noncondensing Turbine Operation of a Multistage Condensing Turbine . . . . . . . . . . Typical Starting Sequence for a Steam Turbine Generator Set . . . . . . . . . . . . . . . . Maintenance . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . IntemaiWaterWashing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Steamhuity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

Section 10 INQUIRY GUIDE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Appendix . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

piec 51 51 51 51 51 52 52 52

55 55 55 55

57 57 57 57 57 57 57 61 61 61 61 64 64 64 65 65 65 68 68 68 71 74

79 79 79 79 79 79 79 80 80

83

86


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~

S T D - N E M A SM 24-ENGL L993 M 6470247 0527203 Bbb

Foreword This standard has been developed by the Steam Turbine Section of NEMA. in its preparation

and revision, consideration has been given to the work of other organizations, such as the American Naionai Standards Institute, the American Society of Mechanicai Engineers, and the American Gear Manufacturers Association, striving toward the development of standards, and credit is hereby given to a l i whose standards may have been helpful in the preparation of this publication.

The purpose of this standard is to facilitate the application of these turbine generator sets by engineers, users, and contractors, to promote economies of steam power generation equipment, and to assist in the pm+r selection and application of the differing designs of steam turbine generator sets.

NEMA Standards Publication SM 24-1991 revises and supersedes the NEMA Standards Publi- cation Land Based Steam Turbine Generator Sets O to 33,000 kw, SM 24-1985.

User needs have been considered throughout the development of this standard, Proposed or recommended revisions should be submitted to:

Vice President, Engineering Department National Electrical Manufacturers Association 2101 L Street N.W., Suite 300 Washington, D.C. 20037

i


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~ ' scope nieSe smndards covet singie stage and muitistage steam Mbines, redPCtion gears, air cooled

elemic generators, switchgear and auxiihy systems. niis staadard is also appkable to turbines expanding various gases or wrnprese air.

In addition, this standard applies to auxiliary equipment 8ssociBtcd with the turbine gememor such as govmors, basephtes, excitation controls, steam piping. and 50 fath. Iht standard dots not apply to other equipment in the steam cycle or electrica distribution systems.

ii


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SM 24-1991 Page 1

Section 1 REFERENCED STANDARDS AND DEFINITIONS

1.1 REFERENCED STANDARDS In this publication, reference is made to the standards listed belw . Copies are available from the indicated sources

American Boiler Manufacturers Association 1500 W&on Boulevard

Arlington, VA 22209

Boiler Water Quality and Steam Pwity Ratesfor Water Tube Boilers (1982)

Amencan Gear Manufacturers Association 1901 North Fort Myer Drive

Arlington, VA 22209

42 1 .O6

C37.W 1989

ANS- 100-1988 S 1.4- 1983 S 1.11- 1986

ANSVASME B 1.20.1-1983 B 16.1-1989 B16.5-1988 B3 1.1-1989

IEEE Standard 1-1986

IEEE Standard 112-1984 IEEE Standard 115-1983 IEEE Standard 200-1975

Practices for High-speed Helical and Herringbone Generator Units

American National Standards Institute 1430 Broadway

New York, NY 10018

Standard for High Voltage Circuit Breakers Rated on a Symmetrical Current Basis-Preferred Ratings and Related Required Capabilities Dictionary of Electrical and Electronic Term Specification for Sound Level Meters Specifications for Octave-Band, Fractional Octave-Band Analog and Digital Filters

General Purpose Pipe Threads (inch) Cast Iron Pipe Flanges and Flanged Fittings, Class25,125,250 and800 Pipe Flange and Flanged Fittings Power Piping

Expansion Joint Manufacturers Association 25 North Broadway

Tarrytown, NY 10591

The Standard of the Expansion Joint Manufacturers Association (1980) (1985 Addendum)

institute of Electrical & Electronic Engineers 345 East 47 street

New York, NY 10017

General Principles for Temperature Limits in the Rating of Electrical Equipment Test Procedures for Polyphase induction Motors ana' Generators Test Procedures for Synchronous Machines Design Electrical & Elecwonic Parts & Equipment (Device Numbers Md Functions)


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STD-NEMA SM 24-ENGL 1991 6470247 0527204 575 II , .. . .. - . .

... .. SM 24-1 991 Page 2

MG1-1987 SM 23-1985 AB 1-1986 250-1985

National Eiectricai Manufacturers Association 2101 L Street, N.W.

Washington, D.C. 2337

Motors and Generators Steam Turbines for Mechanical Drive Service Molded Case Circuir Breakers EnclosUras for Electrical Equipment (loo0 Volts Maximum)

1.2 DEFINITIONS The terms in Section 1.2 are defmedas they apply to land

based steam turbine generator sets covered in this standards publication.

AC Power-Power used in an altemating curtent electricai circuit. (See Appendix.)

Alternating Current (ac)-Cunrent which varies from zebotoapositivemaximumtozerotoanegativemaximum to zero, a number of times per second, the number being expressed in cycles per second or Hertz (Hz).

Atemator-A generator which produces alternating CUrrenL

Ambient Temperature-The temperatwe of the sur- rounding ah in which the generating system operates.

Ammeter-An instrument for measming the magnitude of an electric currenL

Amortisseur-A short-circuited winding consisting of conductors embedded in the pole faces of the rotor of a synchronous generator.

Ampere-The unit of electric current flow. One ampere will flow when one volt is applied across a resistance of one ohm.

Apparent Power-The vectoriai sum of real power and reactive power. (See Appendix.)

Automatic "kansfer Switch-An automatic device for txansfemng an electrical load from one power source to another.

Brushless Exciter-An ac (rotating armatwe type) exciter whose output is rectified by a semiconductor device to provide excitation to an electric machine. The semiconductor device would be mounted on and rotate with the ac exciter mature.

Capacitance-The property of a system of conductors and dielectrics that permits the storage of electrically separated charges when potentiai differences exist between the conductors.

Capacitor-A device, the primary purpose of which is to introduce capacitance into an electric circuit.

Circuit Breaker-A mechanical switching device capable of making, carrying, and breaking circuit conditions and also, making, carrying for a specified time, and breaking cunents under specified abnormal circuit conditions, such as short circuit

Continuous Rating-The load rating of an electrical generating system which it is capable of supplying without

exceeding its specifed maximum tempeaature rise limits for continuous operation.

Cooling Steam-A minimum steam flow which must be passed through a turbine stage to absorb the frictionai heat input resuiting when the airbine rotor is rotated by means other than the n o d expansion of steam through that stage.

Core -An element made of magnetic material, serving as a part of a path for magnetic flux.

Criticai Speed-A speed at which the amplitude of the vibration of a rotor due to shafi transverse vibration reaches a maximum value.

Crass-current Compensation-ne of two systems which permits generators in parallel, to share the reactive component of the power in proportion to their rating while maintaining constant output voltage. See Droop Cornpen- sation.

Cross-current Compensation Transformer (CCCT)- A current transformer which conmls the divi- sion of reactive KVA in Proportion to the rating of generators operating in paraiiel.

Current "kansformer ( C T t A n insrnent transformer used in conjunction with ammeters and control

current. Cycle-One complete reversal of an alternating c m n t

or voltage, from zero to a positive maximum to zero to a negative maximum back to zero. The number of cycles pet second is the frequency, expressed in Hz.

DC Field-The field poles and their winding which, when energized, produce the magnetic flux in a generator.

Delta Connection-A three phase connection m which the staR of each phase is connected to the end of the next phase, forming the Greek letter Delta (A).

Deviation Factor-The deviation h tu r of a voltage wave is the ratio of the maximum diffmce between corresponding orduiates of the wave and of a sine wave of the sameroot-mean-squarevalueandtimebasetothepeaL value of this sine wave when this sine wave is superim- posed in such a way as to make this difemceas smaiias possible.

Diode-Solid state semiconductor which allows c m a t to pass in one direction only.

circuits that produces an output proportianal to primary


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S T D O N E M A SM 24-ENGL 1941 b470247 0527205 401

Direct Current (dc)-Aunidirectionalcurrent in which the changes in value are either zero or so small thai they may be neglected.

Droop-"he change in speed when the power output is graduaily changed from zero power to rated power output and the turbine generator is not paralleled with othe? generating units.

Droop CompensatiowA system which pennits gen- e r a m in parailel to share the reactive component of the power in proportion to their rating..See also Cross Current Compensation.

EXkkncy-The efficiency of a turbine is the ratio (expressed as a percentage) of its useful power output to its net available energy input

Electricai Runout-An apparent deviation in shaft concentricity indicated by the output of a proximity p b e which is due to variations in the electrical conductivity or magnetic properties of the observed shaft surface.

Entrapped Energy-The energy which remains in the volume of steam trapped between the turbine and a trip valve or nonretum valve.

Excitation-The input of dc power into the roiating field coils of a synchronous generator or the input of ac power into the stator coils of an induction generator.

Exciter-" rotating or static device for supplying excitation to the field of a synchronous generator.

Field-A region of space under magnetic influence resulting in a distribution of magnetic lines of flux in that space.

Field Coii-A suitably insulated winding to be mounted on a field pole to magnetize i t

Field Pole-A structure of magnetic material on which a field coil may be mounted.

Flexible Shaft-A shaft which is intended for operation at speeds greater than the first lateral critical speed.

Frequency-The number of complete cycles of an alternating voltage or current per unit of time, usually per second, expressed in Hz.

Frequency Droop-The change in frequency expressed in Hz between steady state no load and steady state full load.

Frequency Reguiation-The percentage change in fre quency from steady state fuil load to steady state no load.

Frequency Recovery Time-The interval of time re- qwred for the frequency to return to and remain within a prescribed frequency band following an instantaneous load change.

Frequency Transient-The maximum frequency deviation as a result of a sudden change in load.

Fuli Load Current-The fuil load current of a generator is the value of current in root mean square (m) or dc amperes which it carries when delivering rated output under rated conditions.

SM 24-1991 Page 3

Generator-A machine that converts mechanical powe? into electric power.

Ground-A conducting connection, whether inten- tionai or accidentai, by which an electric circuit or equip ment is connected to the earth, or to m e conducting body of relative huge extent that serves in place of the earth.

Cmunded Neural-A point of an electrical system which is in ten t idy connecte to ground.

Hertz (Hz)-'Ihe Unit of frequency. one cycle per second.

Hunting-"he oscillation of voltage, frequency, or other cmmiied parameter above and below the mean value. An unstable condition. Hydro Test-A test for leaks and integrity of the pres-

sure containing components of the turbine by pressurizing with water.

mpedanc+The total opposition offered by a circuit to the flow of alternating current It is composed of resistance and reactance (inductive or capacitive, or both), and its symbol ''2'' is expressed in ohms.

inductance-The property of an electric circuit by which a varying current induces an electromotive force in that circuit or in a neighboring circuit.

induction Generator-An induction machine driven above synchronous speed by an e x t e d source of mechanical power for use as a generator.

in-phase-A condition in which the ac voltage waves of two gemrating systems coincide.

Inrusb Current-le inrush current of a machine or a m t u s is the maximum value of rms or dc amperes which it Cames after being suddenly and f d y energized and prior to reaching a stable Operating condition.

Insuiation-Material or a combination of suitable non- conducting materials that provide electric isolation of two parts at Werent voltages.

Internal Water Washing-Aproceure in which steam having a high percentage of moisture is injected into the turbine for the pupse of removing water soluble deposits from the turbine blades and nozzles.

Kilovolt Ampere-Qne thousand volt amperes (apparent power), equal to kilowatt divided by the power factor, also equal to (root mean square) current times (root mean square) volts in kilovolts. (See Appendix.)

Kilovolt Ampere Reactive-ne thousand volt amperes reactive-xeactance power. (See Appendix.)

Kowatt-ne thousand watts (reai power). Equal to kilovolt amperes times power factor. (See Appendix.)

Kilowatt Hour (KWH)-One thousand watts times one hour, unit of electric energy or work.

Laterai Critical Speeds-"he speeds at which the amplitude of the lateral vibration of a machine rotor due to shaft rotation reach their maximum value.


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SM 24-1991 Page 4

Line-to-Line Voltage -The voltage existing between any two conductors in polyphase circuitS. Atso, the voltage between the phase conductom.

Line-teNeutra1 Voitage-The voltage existing between any phase conductor and the neutral conductor.

Manual Transfer Switch-Amanually operated device for ansfemng an electrical load from one power source to another.

Maximum Power-Maximum power is the output power at the generator terminals in kilowatts when Oper- ating with maximum inlet conditions, minimum exhaust conditions, specified power factor, minimum extraction, and maximum induction steam flow, when applicable.

NeutrabThe point common to all phases of a polyphase circuit-it is the point along an insulated winding where the voltage is the instantaneous average of the line tefininal voltage during normal operation.

Non-Salient Pole-A pole structm with its electrical coils wedged in axial slots in a cylindrica body.

Normal Power-Normal power is the power which the turbine generator set wiil produce when operating at specified normal conditions.

OHM-Unit of electrical resistance. One volt wiil cause a current of one amp= to flow through a resistance of one ohm.

Overload Power4verl?d power is that l?d in ex- cess of rated load which the turbine generator unit is capable of delivering for a specified period of time. The voltage, fiequency, and operating temperature may differ from normal rated values.

Out-of-Phase-A condition in which the ac voltage waves of two generating systems do not coincide.

Parallel Operation-Two or more generators of the same phase, voltage, and frequency characteristics supplying power to the same load.

Paralleling-The procedure used to connect two or more generators to a common load.

Permanent Magnet Generator (Pilot Exciter)-A generator in which the open-circuit magnetic flux field is provided by one or more permanent magnets.

Phase-The number of complete voitage or current sine waves, or both, generated per 360 elecmcal degrees.

Phase Angle-The amount by which the zero point of the voltage wave differs from the zero point of the current wave in an ac circuit (See Appendix.) Phase Rotation-The sequence in which the phases of

a generator or network pass through the positive maximum points of their waves. The same sequence must exist when units are paralleled.

Phase Sequence-The order in which the voltages suc- cessively reach their positive maximum values between temiinalS.

Pole-A machine structure which generates and directs lines of magnetic energy.

Potential 'hamformer (Voltage 'Itansformer)-An instrument transformer that is intended to have its primary winding ~ o n n e ~ t e d in shunt with a power supply cinuit, the voltage of which is u) be measured or controe.

Power Factor-The ratio of real power divided by a p n t power. (See Appendix.)

Proximity Probe-A non-contacting device which elecmnically measures the position or disphcernait mo- tion of an observed surface relative to the probe position.

Purge Air-A method of sealing in which air (or inert gas) is bled into the seal or housing to maintain a slight positive pressure and thus prevent the entrance of contam- inants.

Rated Current-The rated current of a generator is the value of current in rms or dc amperes which is obtainable from a aubine generator set when it is functioning at rated conditions. See Full Load Current.

Reactance -?he out-of-phase component of impe- ance that occurs in circuits containing inductance or capacitance, or both.

Reactive KVA (KVAR)-The reactive component of ac power. (See Appendix.)

Real Power-?lie real component of ac power. (See Appendix.)

Reduction Gear-A mechanical device used to reduce the turbine speed to the generator speed.

Reiay-A device which initiates an output change as a response to a specified input change.

Resistance Temperature Detector (RTDbA device for measuring temperature in which the elecaical mis- tance of the device changes with temperahire.

Response Time-The time required to recover to the steady state operating value after a sudden change in load.

Root Mean Square (rms)-A measurement of altem- ing current and voltage and representing a proportional value of the true sine wave.

Salient P d e - A pole structure and its elecaical coils which pmject from a hub or yoke.

Service Factor-The factor by which the maximum power capability of a device exceeds its rated power.

Short Circuit Ratio-The ratio of the field current for rated open-circuit armature voltage and rated frequency to the field current for rated armature current on sustaincd symmetrical short-circuit at rated equency.

Short Term Rating-The load rating of an electrical generating system which it is capable of Carrying for a short specified period of time.

Silicon Controlled Rectifier (SCRtSolid state ds vice which permits current to flow in one direction oniy when higged by a suitable potential applied to the con- rnl lead or tenninal.

Spedfied ConditionsSpecified conditions are all customer defined power, voltage, frequency, power h u x


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STD-NEMA SM 2'4-ENGL 1771 64702'47 O527207 284

SM 24-1991 Page 5

and steam conditions at which the nirbine generam must openite-

Static Exciter-A non-mtating device which fmishes direct current to the generator field.

Stator-The portion of a generator which includes and supports the stationary active parts.

Stator Winding -A winding on the stator of a machine.

Steady State -The operating pokt under constant load when no transients are present,

Steam 'Iiirbine-A prime mover which converts the themud energy of steam directly into mechanical energy of rotation.

normalcircumstancesatspeedsgreaterthanthefirst~

Switchgear-A general term covering switching and intempting devices and their combination with associated control, instrumentation, metering, protective and regulating devices. It ais0 includes assemblies of these devices, associated interconnections, accessories, and supporting smctures used in connection with the generation, transmission, distribution, and conversion of electric power.

Synchnous Generator-A synchronous ac machine which transforms mechanical power into electrical power and operates at synchronous speed at any load. Excitation is supplied by a generator exciter.

Synchronous Speed-The generatar speed which is directly proportional to the frequency of the system to which the generator is connected. (See 2.4.2 1.)

Synchronizing-The process whereby a synchronous machine, with its voltage and phase suitably adjusted, is paraiieled with another synchronous machine or system.

Telephone Influence Factor (TIF)-The telephone influence factor of a synchronous generator is a measure of

Stiff Shaft-A shaft which will not be operated during

critical speed.

the possible effect of harmonics in the generator voltage wave on telephone circuits.

Thermocouple-A device for sensing temperaaats in which a pair of dissimilar conductors are joined at two points so that an electromotive force is developed by thermoeiectric effects when the jwictions are a Mennt temperatInes.

Torsional Criticai Speed-The speed at which the am- plitudes of the anguiar vibrations of a machine rom due to shaft torsional vibration reach a maximum.

'ikanslormer-A static electric device that inaoduces mutual coupihg between electric circuits.

Voit-The unit of electromotive fm. One volt wiii cam a current of one ampenz to flow through a resistance on one ohm.

Vdtage Dip-he maximum reduction in voltage IG suiting from an increase in load.

Vdtage Range-The voltage range of a generatur is the band widh of voltage through which the generator is capable of adjustment and operation from no load through full load at specifed conditions.

Vdtage Regdation-The voltage reguiation of a generator is the difference between the regulated no load and the reguiated full load output voltage expressed as a percentage of the regulated fuil load voltage.

Vdtage Regulator -A device which maintains the voltage output of a generator.

Vdtmeter-An instrument for measuring the voltage magnitude.

Wye Connection-A method of interconnecting the phases of a three phase system to form a conguration resembling the letter "Y". A fourth ar neutral wire can be connected to the center point.

NEMAStandard 6-12-1985.


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STD.NEMA SM 24-ENGL LL 61i70247 0527208 IL0 m

SM 24-1991 Page 7

Section 2 CONSTRUCTION

2.0 GENERAL

2.0.1 Introductbn A steam turbine generator set includes a steam turbine,

reduction gear (when applicable), and a generator. The steam turbine converts energy from the available

heat drop between two or more steam pressure levels into shaft power. The reduction gear, when applicable, allows the turbine to operate at an efficient speed and matches the output speed to the generator speed

The generator converts the shaft power into electrical output at the generator terminals. The turbine generator controls reguiate the steam flow

and generator excitation to produce stable operation. Authorized Engineering Inhation 130-91.

2.1 TYPES OF STEAM TURBINES 2.1.1 Ciassified by Exhaust Condltbns

2.1.1.1 NONCONDENSING TURBINE A noncondensing turbine is a steam turbine designed to

operate with an exhaust steam pressure equal to or greater than atmospheric pressure.


2.1.1.2 CONDENSING TURBINE A condensing turbine is a steam turbine designed to

operate with an exhaust steam pressure below atmospheric pressure.

2.1.2 Cbsslfled by Number of Stages and Control Valves

2.1.2.1 SINGLE VALVE SINGLE STAGE TURBINE A single valve single stage turbine is a steam turbine

which has one governor controlled valve and one stage. NEMAStandard 6-21-1979.

2.1.2.2 SINGLE VALVE MULTISTAGE TURBINE A single valve multistage turbine is a steam turbine

which has one governor controlled valve and two or more StageS.

2.1.2.3 MULTIVALVE SINGLE STAGE TURBINE A multivalve single stage turbine is a steam turbine

which has two or more governor controlled valves and one stage.


NEMAStandad 6-21-1979.

2.1.2.4 MULTIVALVE MULTISTAGE TURBINE A muitivaive multistage Wine is a steam turbine which

has two or more govemor controlled valves and two cr more stages.

2.1.3 CiassJfled by Proce99 Nees 2.1.3.1 -0 (AurouLITic) EXTRACTKM


TURBINE A controlled (automatic) extraction turbine is a steam

m i n e which has an opening(s) in the turbine casing far the extraction of steam and which is provided with means for directly regulating the flow of steam to the turbine stages following the extraction opening for the purpose of conmiiing extraction pressure.

NEMA standad 6-21-1919.

2.1.3.2 NO"TROUED EXTRACTION TURBINE A noncontrolled extraction turbine is a steam turbine

which has an openin&) in the airbine casing for the extraction of steam but which does not have means far controlling the pressure of the extracted steam.


2.1 3.3 NO"TROUED INDUCTION TURBINE A noncontroiied induction turbine is a steam turbine

which has an opening(s) in the turbine casing for induction of steam but which does not have means for controiiing the pressure of the inducted steam.

NEMA Standard 1 1 -1 4-1 085.

2.1 3.4 CONTROLLED INDUCWON (MIXED PRESSURE) TURBINE

A controlled induction (mixed pressure) turbine is a steam turbine which is provided with separate iniets for steam at two pressures and has an automatic &vice for controlling the flow of steam to the turbine stages folow- ing the induction opening.


2.1 3.5 INDUCTION EXTRACTION TURBINE An induction extraction turbine is one which combines

the f e a m of extraction (controlled or noncontrolle) with the feaaires of induction.

2.2 STEAM TURBINE COMPONENTS

NEMA Standard 6-21-1819.

2.2.1 nirblne caslng A turbine casing is the enclosure which s m u n d s the

rotating element of the turbine and supports the stationary


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SM 24-1991 Page 8

steam parts casings shall be axially split, radially split, Oc a combination themf.

sections as follows: zhe turbine casing shaii be divided into two oc more


22.1.1 SIEAM INLET END SECTION

which contains the higher prekure steam.

22.1.2 EXHAUST END SECTION The exhaust end section is that portion of the casing

which contains the exhaust connection and the steam at exhaust conditions. It shall also contain the low pressure stage@) of a multistage turbine.

The steam inlet end section is that portion of the casing

NEM4 Standard 6-21 -1979.


22.1 3 ~NTEFtMEDinTE SECTION The intermediate section (multistage turbines only) is

that portion of the casing which is between the steam inlet end and the exhaust end sections and which contains the intennediate stage(s).

N E W Standard 6-21-1979.

2 2 2 Steam Chest (Governor Value Body) A steam chest (governor valve body) incorporates the

inlet connection. hoYses the governor controlled vaive(s), and is bolted to or integral with the steam ring inlet section.

2.2.3 SteamRing A steam ring incorporates the passage(@ through which

the steam flows from the governor valve(s) and steam chest to the first stage nozzles.

2 2 4 Nonles Nozzles are stationary machid or formed openings

which expand the steam and direct it against the turbine blades or buckets.

225 Stationary Reversing Blades Stationary reversing blades in a velocity-compounded

stage redirect the steam flow Com one row of rotating blades or buckets to the foilowing rotating blades or buckets.


NEWStandard 6-21-1979.

NEMASEandard 11-13-1969.

NEMA S W r d 11-13-1969.

226 Stationary Reversing Chambers Stationary reversing chambers in a reentry velocity-

compounded stage redirect and return the steam flow to the preceding rotating row of blades or buckets.

227 Diaphragm Adiaphragm is the stationary element of a stage contain-

ing nozzles which expand the steam and direct it against the rotating blades. It is normally used in a multistage turbine.

228 Stage, Tuaine A steam turbine stage consists of a matched set of

stationary nodes and rotating biades. A pressure drop occm in a steam turbine stage generating kinetic energy which is converted to mechanical work.

2.2.8.1 IMPULSE STAGE An impuise stage consists of stationary expansion noz-

zie(s) discharging the high velocity steam jets on the rotating blades. Apressure drop occurs only in the stationary nozzie(s). impulse stages consist of three types:

2.2.8.1.1 A pressure impulse or Rateau stage consists of stationary expansion node(s) and one row of rotating blades.


2.2.8.1.2 A velocity-compounded impulse or Curtis stage consists of stationary expansion noule(s) and two ar more rows of rotating blades.

2.2.8.1.3 A velocity-compounded impulse reentry stage consists of stationary expansion nozzie(s), one row of rotating blades and one or m m reversing chambers.

The pressure drop across a Rateau stage is datively low in comparison to the pressure drop across a Curtis stage.

Authorized Engineering Information 6-21-1979.

2.2.8.2 REACT~ON STAGE A reaction stage consists of stationary expansion noz-

zie(s) discharging high velocity steam jets on the rotating blades A pressure drop occurs in both the stationary and rotating elements.

2 2 9 ShatSeals


2.2.9.1 CASING S u n SEALS Casing shaft seais minimize the leakage of steam Out of

the casing along the shaft. For condensing turbines, seals are arranged IO prevent

the entrance of air into the casing along the shaft hey arc ananged for the admission of steam at a constant low pressure and low temperature.

2.2.9.2 INTERSTAGE S H A ~ SEALS

along the shaft between stages in a multistage turbine.


interstage shaft seals minimize the leakage of steam



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STD-NEMA SM 24-ENGL 3993 6 4 7 0 2 4 7 0 5 2 7 2 3 0 879 M

2.2.10 Bearing Housing A bearing housing contains and supports a bearing@

and is equipped with seals to pvent leakage of oil and the entrance of moisture, dust, and fmign materials.


2.2.1 1 Bearings

2.2.11 .l RADIAL BEARINGS Radial bearings are bearings which support the rotating

element in horizontal shaft turbines. They are of the sleeve, tiiting pad, or antifriction type. in vertical turbines, these bearings radially position the TOM assembly.


2.2.11.2 THRUST BEARINGS Thrust bearings are bearings which lransmit the axial

thrust of the rotating element to the bearing housing and maintain the axial position of the rotor assembly in the casing. They are of the antifriction, land, or segmental tilting pad type.


2.2.11.3 ANTIFRICTION BEARINGS Antifiction bearings should have a minimum mthg life

of 3 years or 25,000 hours when operated continuously at maximum thrust and radial loads and at rated speed.

Authorized Engineering Information 6-21-197Q. The rating life is the number of burs at constant speed

that 90 percent of a group of identical bearings will operate before the first evidence of fatigue develops.

Authorized Engineering Infomiation 6-21 -1979.

2.2.1 2 Rotor Assembly The rotor assembly is the rotating element of the turbine

which includes dl parts attached to the shaft, excluding the coupling(s) unless coupling is integral with the shaft.

NEMA Standard 6-21 -1979.

2.2.13 Wheels (Discs) Wheels are discs which are integral with, or fmed to. the

turbine shaft and on which blades are mounted, or in which blades or buckets are machined.

NEMAStandard 6-21-1979,

2.2.14 Blades (Buckets) Blades (buckets) are curved vane elements proportioned

to convert kinetic energy of the steam to mechanical energy.

2.2.15 Shroud


A shroud is an integrai or separately attached rim located at the blade tip. The shroud prevents radiai leakage of the steam jet and increases the blade rigidity,

NEMA Standard 6-21-1979,

SM 24-1991 Page 9

2.2.16 Hand Vhr(S) A hand valve@) is the Valve which isolates steam flow

to a nozzle or a group of nozzles to pennit efficient operation at reduced power or with dual steam conditions. Hand valves can be either manually conolled or auto- mated, and are used on single valve turbines only.


2.2.17 Protecthre Device A protective device is one which, alone or as part of a

system, responds in some predetermined manner to abnormai conditions amding the operation of the unit or system to which it is c o ~ e ~ t e d .

2.2.18 COMrolling Devlce A controlling device is one which manually or automat-

ically initiates action of a system which conmls normai opemion of the turbine.

2.2.19 Extemai control pavke An extenial control device is an element which is re-

sponsive to signais other than turbine speed, i.e., flow, pressure, temperature, and so forth, and acts to control the flow of steam to the turbine. It shall be pneumaticay, mechanically, hydraulically, or eleciricaliy actuated h m the signai source to position the governor valve(s). (Ref- erence Section 3.1.6.)

2.2.20 warning A warning device is one which, by visible or audible

means, or both, indicates that an abnormal operating condition exists.



NEMA Standard 6-21-1979,


2.2.21 Sentlnel Warnlng Valve A sentinel warning valve is a pressure warning device

which opens when the steam pressure rises to a predetermined level. The device shail discharge to the atmosphere and shall be so located as to be plainly visible.

For condensing turbines. it shall be set at 5 psig [35 kPa (gauge)]. For noncondensing turbines the minimum set- ting shail be either 10 percent or 10 psi (70 kPa) above maximum exhaust steam pressure, whichever is greater,

A sentinel warning valve is not recommended for the following applications:

turbines which expand volatile gases locations where the discharge of steam to the atmosphere is objectionable, hazardous, or prohibited by h W turbines which are arranged for automatic and/or unat- tended start-up

NEMASiandard 6-21-1979.


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, . . . ,

SM 24-1 991 Page 10

For these applications, an alteniate wamhg device or

Authorized Enginsering Information optionai hip device is recommended.

2.2.22 Soleplate(8) A soleplate@) is a machined flat steel plaie(s) or cast-

ing(s) for mounting of the equipment supports and far bolting and grouting to the foundation.


2.2.23 Baseplate A basepiate is a fabricated or cast continuous stnicture

having machined pads for mounting of the equipment and for bolting and grouting to the foundation.

The turbine generator set shall be mounted on a baseplate, soleplates. or a combination of both.

2 3 FEATURES AND ACCESSORIES


2.3.1 Basic Features and Accessories

2.3.1.1 STEAM TURBINE ITEMS Steam turbines shall include at least the following basic

features which are deemed necessary for proper functioning and safety of operation.

i. Steam strainer with removable corrosion-resistant element.

2. Control system. 3. Overspeedtripsystem. , 4. Provisions for lubrication. 5. Exhaust casing gland sealing connection (for con-

densing turbines only). 6. Eyebolts or other provisions for lifting the upper half

of the casing on an axiaiiy split turbine.

2.3.1.2 GEAR ITEMS Parallel shaft gears shail include at least the following

basic features which are necessary for proper functioning and safety of operation.

1. Casing to enclose the rotating elements of the gear. 2. Rotating elements having gear teeth with surface

quality, hardness, and strength to provide long service life.

3. Bearings to support rotating elements. 4. Covered opening to aliow for internal inspection. 5. Provisions for lifting the upper haif of the gear

casing. 6. Provisions for lubrication. 7. Couplings and coupling guards.


2.3.1.3 GENERATOR ITEMS The generator shall include at least the following basic

feam which are deemed necessary for proper functioning and safety of aperation: 1.

2.

3.

4.

5. 6. 7. 8.

Enclosure to guard against the entrance of moisture, dustandfateignobjectSintothegenerator.~oopen dnpproof enclosure shaii be the basic enclosure far a generator driven by a steam turbine. Frame which rigidly supports the machine to p vide low vibration and long life. Stator composed of a support structure and a core made up of electrical steel lamination and insulated windings (coiis). The stator shall be set into the frame in a way which will pennit the circulation of cooling air mund the core. The insulation system shaii maintain its insdating properties at the maximum operating rated temperam as specified in 2.12.12 (Temperam Rise). Rotor consisting of the shaft, field poles, field windings, and me or more fans to circulate cooling air. The rotating element of the exciter shaii be mounte on the rotor shat The coupling, if integral with the shaft, is also part of the rotor. The insulation sysEm shall maintain its insulating properties at themaxi- mum operating rated temperam as specifed in 2.12.1.2 (Temperature Rise). Bearings to support the mtor. provisions for lubrication. Power terminals. Excitation system far synchronous generators oniy. The basic excitation system shail be the brushless type with a rotating armatme generating a 3 phase ac voltage with fuli wave rectification to dc for field excitation.

2.3.2 Optlonai Features and Accessories

2.3.2.1 STEAM TURBINE OPnoilss in addition to the feanires listed in par. 2.3.1.1, the

following are optional features and accessories which may be selected &pending on the application.

1.

2. 3.

4.

conmi systenis with option for pressure conmi ar load sharing. Hand vaivds) for single Valve turbines. Combinedhipandthrottlevalvewhichincorporates into one assembly a means for gradual opening and adjustment of inlet steam flow as well as a means for rapid and complete shutoff of that flow. Solenoid hip which allows an electrical protective device(s) to act through a hydrauiic, pneumatic, ar mechanid hipping system to shut off steam flow into the turbine.


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STD*NEMA SM 24-ENGL 1991 6470247 0527232 641

5. Trip system which can be tested during operation. 6. Trip or alarm initiating devices which respond to

abnormai conditions such as: a. low oil pressure b. high bearing temperature c. high vibration d. high axial shaft movement e. highsteampressure f. high steam temperature g. high oil temperature h. high or low oil reservoir level i. speed pickup failure j. governor failure k. loss of exhaust vacuum 1. high exhaust temperature

7. Oil sight flow indicator@) in drain piping of pressure lubricated systems.

8. Constant level oilers for non-pressure oil lubricated systems.

9. Insulation for the high temperature section of the turbine to limit exposed surface temperature to 165% (74OC) or other temperature specified by the purchaser.

10. Steampressuregaugestoindicate inietsteam,steam ring, rst stage, and exhaust steam pressure.

11. Gland leakage evacuating apparatus when the gland casing design requires its use.

12. Tachometer of the vibrating reed, mechanical, or electrical type; indicating speeds from above the trip speed to below the minimum operating speed. Ta- chometers shaii be suitable for the specified envi- ronment.

13. Supervisory instruments to monitor such as vibration, axial shaft movement, temperam, etc.

14. Shaft grounding device to wry to ground any static charge which might be developed on the nubine rotor and which may otherwise build to levels which could damage turbine bearings.

15. Rotor turning gear together with driving means, engagement and disengagement featues, and lube oil pressure interlocks M permit slow w i n g of the rotor system on start-up and shutdown.

16. Admission trip valve which provides a means for quick and positive shutoff of admission steam for emergency tripping.

17. Nonretum vaive($ for blocking the reverse flow of steam from process into the turbine through exhaust or extraction openings.

18. Redundant overspeed trip. 19. Exhaust relief valve or rupture disc to prevent over-

pressuring of the exhaust end section (see Section 8.7).

SM 24-1991 Page 11

Z. Vacuum breakei to admit air into the exhaust of a to reduce coastdown condensing turbine in

. time. Additional items may be available.

Authorized E n g M n g Information 130-1991.

2.3.2.2 GEAR The following are accessories which may be selected,

depending on rating and applidon: 1. Beaxing temperahire indicators. 2. Vibmtion monitoring devices. Additional items may be available.

Authorized Enginwing Infomiation 1-30-1991.

2.3.2.3 GENERATOR O m The foiiowing are accessories which may be selected,

depending on ratings, voltage, and applications: 1. Enclosure other than d r i p - p f type where necessi-

tated by environmental conditions. 2. stator temperam indicatars. 3. Bearing temperature indicators. 4. Vibration monitoring devices. 5. Spaceheaters 6. Terminaibox. 7. Surge suppressors/capacitors. 8. Lighiningarresters. 9. Current transformer(s) 10. Potential transformer(s) 11. Circuit breaker trip or alarm in response to any of

the following functions: a. highstatortemperatm b. overhnder voltage c. overhinder frequency d. reversepower e. differential protection f. high coolant temperam (air or water) g. groundfault h. open phase/phase balance i. loss of excitation j. turbine trips

12. Other accessoneS are available.

2.3.3 Controlled Extraction and Controlled induction Tubines

Controlled extraction, controlled induction, and controlled induction extraction turbines shall include basic features listed in items 1 through 6 of par. 2.3.1.1, together with those listed in 2.3.3.1 through 2.3.3.4.

2.3.3.1 Controlled extraction turbines shall have a pressure regulating system for controlling the pressure of the extracted steam by regulating the flow of steam to the turbine stages following the extraction opening(s). Anon- retum valve for the extraction opening@), which is also


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SM 24-1991 Page 12

actuated by the overspeed trip system, is required for instaliation in the exmtion steam line(s).

2.3.3.2 Conmlled induction turbines shail have a pressure regulating system for controlling the pressure of the induction steam to regulate the flow of steam to the turbine stages following the induction opening. A trip valve which is also a c d by the overspeed trip system is required for installation in the induction steam line.

NEMAStandard 1-91.

2.3.3.3 Depending on the source of induction steam, the user should consider the need for a steam strainer in this line to protect the lower pressure stages of the turbine.

Authorized Engineering Infomation 11-14-1985.

2.3.3.4 Controlled extraction turbines and controiied induction turbines shall have a multivariable conml system which provides interconnection between the pressure regulating system and the speed governing system.

2.3.3.5 Controlled induction extraction turbines shall include the combination of the foregoing items.

23.4 Noncontrolled Extraction Tutbines Noncontrolled extraction himines shall include the basic

features listed in items 1 through 6 of par. 2.3.1.1, together with nonretuni valve(s) for the extraction opening(s). The quantity and location of nonretuni valves are to be deter- mined by the turbine manufacturer based on entrapped energy and redundancy policy.

23.5 Noncontrolled Induction Turbines Noncontrolled induction airbines shall include the basic

features listed in items 1 through 6 of 2.3.1.1, together with a trip valve(s) for the induction opening(s).



NEMStandad 11-14-1985.

2 4 TURBINE GENERATOR RATING

24.1 Power The basis of rating of the turbine generator set shall be

the power output in kilowatts at the generator terminals when operating at the steam conditions, voltage, and power factor specified by the pmhaser. nie rating of the generator shall be the real output power

in kilowatts measured at the output mina i s when the generator is operating at the design power factor, voltage, and kquency under design environmental conditions. The rating shall include the excitation power requirements. The power absorbed by a separate excitation system, when supplied, shali be deducted from the real output power at the generator terminals.

NEMAStandard6-12-1985.

The rating may also be the apparent output power in kilovolt-amperes measured at the output texminals at design operating conditions.

24.2 Frequencyandspeed Frequency of power generated shall be 50 or 60 Hz.

Other frequencies are available for special appiications. Generators will employ one or more pairs of rotating field poles to produce the desired frequency of ac power output.

2.4.2.1 RATED SPEED, GENERATOR

power output fkquency by the equation:

Authorized yineerirg Informaiion 6-1 2-1 96.

Rated speed of a synchronous generator is related to

ISOF N=-- P where F = frequency in Hertz

N = synchronous speed in rpm P = numbers of poles

Rated speed of an induction generators will be 1-2 percent above synchronous speed, as a positive dip is necessary in order to convert mechanical input to electrical output.

2.4.21.1 Overspeed UmWions Generators shall be 90 constructed that, in an emergency,

they will withstand without mechanical injury ovaspeeds above synchronous speed in accordance with the following:

ovcrspecd, Percent of Synchronous Speed, RPM Synchronous speed

180 1 and over 1800 and below

20 25


2.4.2.2 RATED SPEED, TURBHE Rated turbine speed will be the same as rated generator

speed if directly coupled without a gea. On geared turbine generators the rated turbine speed will exceed the generator speed and will equal the product of rated generator speed and gear ratio.

2.4.3 Voltage The generator voltage shall be specified by the user.

Typical voltages are as shown in Table 2- 1.

2.4.3.1 VARIATIONS FROM RATED VOLTAGE, SYNCHRONOUSG~ERATORS

NEMAStandard 130-1991.

Synchronous generators shall operate successfully at rated NA, frequency and power factor at any voltage not


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SM 24-1991 Page 13

Table 2-1 TYPICAL VOLTAGES FOR TURBINE DRIVEN GENERATORS

ElzVdtage 120 240 208 480 2400 4160 415oYrt100 72011 1#)00 12470 13800 SoHzVdUge 120 240 - 100 1900 3300 33OoY/1900 6600 llOO0 u m

PEASES 1 1 3 3 3 3 3 3 3 3 3

ILW KVA Rating RaUng

100 500 1000 1sW 2Ooo wx) 3000 4OoO Soo0 m 7500 loo00 12500 15OOO 20000 3oooo 33000

125 6.25

1250 1875 2500 3 125 3750 5000 6250 7500 937s

12500 15625 18750 25m 37500 41250

X X X X X X X X

X X X X X X X X X

X X X X X X X X X X

X X X

X X X X X X X X X X X X X X X X

X X X X X

X X X X X X X X X X X X X X



NOTE: M e r voltagca such na 600 V and 6900 V may be ivlilible at tbe n h n i ahown for 480 V md 7ux) V rwDcctivcIv.

more than 5 percent above or below rated voltage but not necessarily in accordance with the standards or performance established for operation at normal rating.


2.4.3.2 VARIATIONS FOR RATED VOLTAGE AND FREQUENCY, INDUCTION GENERATORS

Induction generators shall operate successfully under running conditions at rated load with a variation in the voltage or the frequency up to the following:

1. Plus or minus 10 percent of rated voltage, with rated frequency.

2. Plus or minus 5 percent of rated frequency, with rated voltage.

3. A combined variation in voltage and frequency of plus or minus 10 percent (sum of absolute values) of the rated values, provided the frequency variation does not exceed plus or minus 5 percent of rated frequency.

Performance within these voltage and frequency variations will not necessarily be in accordance with the standards established for operation at rated voltage and frequency.

Authorized Engineering Information 130-1991.

2.4.3.3 MAXIMUM DEVIATION FACTOR

minai voltage of generators shall not exceed O. 1.


The deviation factor of the open circuit line-to-line ter-

NEMA Standard 140-1991.

- Authorized E~ineerhg Inhat ion 6-12-1985.

2.4.4 Steam Conttions 2.4.4.1 MNIMUM STEAM CONDITIONS Minimum steam conditions are the lowest iniet steam

pressure and temperature and lowest exhaust pressure to which the turbine is subjected in continuous operation.

2.4.4.2 MAXIMUM STEAM CONOmCmS Maximum steam conditions are the highest inlet steam

pressure and temperature and exhaust pressure to which the turbine is subjected in continuous operation.

2.4.4.3 MINIMUM ENERGY STEAM CONDITIONS



Minimum energy steam conditions are the lowest inlet steam pressure and temperature and the highest exhaust pressure at which the turbine is required to produce a specifed power and speed.

2.4A.4 NORMAL STEAM CONDITK)P(S N o d steam conditions are the pressures and tempex-

atures to which the turbine is subjected during specified normal operation.

The steam conditions used for rating the turbine generator set shaii be the nonnai steam conditions unless otherwise specified by the user (purchaser).


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SM 24-1991 Page 14

2.4.4.5 INLET STEAM PRESSURE Inlet steam pressure is the pressure of the steam supplied

to the turbine. It is measured at the steam inlet connection of the turbine and is expressed as a gauge pressure.


2.4.4.6 EXHAUST ST-EAM PRESSURE Exhaust steam pressure is the pressure of the steam

system to which the turbine exhausts. It is measured at the exhaust connection of the turbine and is expressed as a gauge pressure for noncondensing turbines and as an absolute pressure for condensing turbines.

2.4.4.7 EXTRACTKIN STEAM PRESSURE Extraction steam pressure is the pressure of the steam

extracted h m the turbine. It is measured at the extraction connection of the turbine, and is expressed as a gauge Pressure-

2.4.4.8 INDUCTION STEAM PRESSURE



Induction steam pressure is the pressure of the secondary steam supplied to the turbine. It is measured at the induction connection of the turbine and is expressed as a gauge pressure.

2.4.4.9 INLET STEAM TEMPERATURE Inlet steam temperature is the total temperature of the

steam supplied to the turbine. It is measured at the steam inlet connection of the turbine and is expressed in degrees Fahrenheit or in degrees Celsius.


NEMA Standard 6-21 -1 979.

2.4.4.10 EXHAUST STEAM TEMPERATURE Exhaust steam temperature is the total temperature of the

steam exhausted from the turbine. It is measured at the exhaust connection of the turbine and is expressed in degrees Fahrenheit or in degrees Celsius.


2.4.4.1 1 EXTRACTION STEAM TEMPERATURE Extraction steam temperature is the total temperature of

the steam extracted bom the turbine. It is measured at the extraction connection of the turbine and is expressed in degrees Fahrenheit or in degrees Celsius.

2.4.4.1 2 INDUCTION STEAM TEMPERATURE

NEMA Standard 6-2 1-1 979.

Induction steam temperature is the total temperature of the secondary steam supplied to the turbine. It is measured

at the induction connection of the turbine and is expressed in degrees Fahrenheit or in degrees Celsius.


2.4.4.1 3 hhXWUM ALLOWABLE WORKING PRESSURES AND TE~RPERATURES

Maximum allowable working pressures and tempera- tures are the maximum contintous conditions for which the manufacnirer has designed the equipment or any part thereof.

They are not normally to be considered as operating conditions.


2.4.4.14 DUAL STEAM CONDITIONS Dual steam conditions are two or more combinations of

inlet steam pressure, inlet steam temperature, or exhaust steam pressure.

N E M Standard 6-21-1979.

2.4.4.15 VARIATIONS IN STEAM CONDITIONS The rating, capability, steam flaw, speed regulation, and

pressure control shall be based on operation at maximum steam conditions as defined in 2.4.4.2. Steam turbines shall be capable of operating under the

following variations in inlet pressure and temperature. but performance shall not necessarily be in accordance with the standards established for operating at maximum steam conditions. Continuous operation at other than maximum steam conditions shall require review by the turbine manufacturer.

2.4.4.15.1 Variations from Maximum Inlet


steam Pressure The turbine shall be capable of operating without dam-

age at less than the guaranteed steam flow to the turbine with average inlet pressure of 105 percent of maximum inlet steam pressure. (This permissible variation m g - nizes the increase in pressure with decrease in steam flow encountered in operation.)

The inlet steam pressure shall average not more than maximum pressure over any 12 month operating period.

nie inlet steam pressure shall not exceed 110 percent of maximum pressure in maintaining these averages, except during abnormal conditions.

During abnormal conditions, the steam pressure at the turbine inlet connection shall be permitted to exceed maximum pressure briefly by as much as 20 percent, but the aggregate duration of such swings beyond 105 percent of

* The use of the word "design" in any tam (such u design pmsum or trmptniurc) should be avoided in thc pirchasers' spccifiutions. Such terminology should be uscd exclusively by the cquipent designer and/or manufacturer.


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maximum pressure shall not exceed 12 hours per 12 month

NEMA Standard 6-21-1979. operatingmod.

2.4.4.15.2 Varlatlons from Maxlmurn InM Steam Temperature

The inlet steam temperague shail average not more than maximum temperature over any 12 month operating period.

in maintaining this average, the temperature shall not c d maximum temperature by more than 1- (8'0 except during abnonnal conditions. During abnonnal conditions, the temperature shaii not exceed maximum temperam by more than 2 5 9 (14OC) for operating periods of not more than 400 hours per 12 month operating period nor by more than 50% (28OC) for swings of 15 minutes duauon or less, aggregating not more than 80 hours pet 12 month operating period.


2.4.4.15.3 Varlatlons frwn Maximum Exhaust Steam Pressure on Noncondenslng nirblneS

The exhaust steam pressure shall average not more than the maximum exhaust steam pressure over any 12 month operating period.

in maintaining this average, the exhaust steam pressure shali not exceed maximum pressure by more than 10 percent nor drop more than 20 percent below maximum exhaust pressure.

2.4.4.1 5.4 Variations in Exhaust Steam Pressure on Condenslng nirblnes

Any anticipated variations in the exhaust steam pressure should be specified by the user so that it can be taken into consideration in the design of the turbine.


2.4.4.16


FLOW LIMITS FOR AN AUTOMATIC EXTRACTION TURBINE

An automatic exuaction turbine may be designed so that, when operating with extraction flow and with only cooling steam flowing to the exhaust, it wili develop the rated power of the turbine.

Good design practice indicates that the maximum ex- m u o n flow ratio should be held to 2.5 or less. (The extraction flow ratio is the ratio of the total extraction flow to the nonextracted rated load flow.)

Authorized Enginehng Information 11-13-1969,

SM 24-1 991 Page 15

2.4.4.17 FLOW LIMITS FOR AN INDUCTtN TURBINE An induction turbine may be designed for a steam flow

h u g t i the low pressure sraga equal to the flow of low pressure steam done that is required to produce the rated power of the turbine.


2.45 Units ot ~easurement for Abaute ress su re and GaugePressure

Steam pressure values should be clearly stated as gauge pressure or absolute pressure. Gauge pressure equals a b solute pressure less amiospheric pressure. Gauge pressure is measiired in psig @ouns per square inch gauge) or in kPa (gauge) (kilopasah gauge). Absolute pressure is measured in psia (pounds per square inch absolute) or in kPa (absolute) (kilopascals absolute). Unless otherwise stated, atmosph& pressure is assumed to qual 14.6% psi or 101.325 kpa. To convert from psi to kpa, multiply by 6.894757.

2.5 THERMODYNAMIC TERMS

2.5.1 Steam and Heat Rates 2.5.1.1 THEMETICAL STEAM RATE*

"heoretical steam rate is the quantity of steam per unit of power required by an ideal Rankine cycle heat engine. It is expressed in pounds of steam per kilowatt hour or in kilograms of steam per kilowatt hour.

3413 Theoretical steam rate i n p o u n m = - hi-b

3600 Theoretical steam rate in Kg/KWH = - h i 4 2

Based on Keenan, Keyes et. ai. Steam Tables (international Edition - Metric Units) or other steam tables or Mollier charts, which are in accordance with the Intema- tiona Skeleton Tables of 1963 of the Intemational Confer- ence on the Propezties of Steam that are expressed in jouies per gram or kilojoules per kilogram, or based on Keenan and Keyes Steam bles published in 1%9 expressed in Btu per pound, where:

hi - the enthalpy of steam at inlet steam pressure and temperature.

hz -the enthalpy of steam at exhaust steam pressure and initial entropy.

with h in kilojoule per kilogram


2.5.1.2 ACTUAL STEAM RATES' Actuai steam rate is the quantity of inlet steam required

by the turbine generator per unit of power output measure

* Stum rate dou not apply to exmctim 01 inductim turbine gmentcnx.


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SM 24-1991 Page 16

at the generatap terminals. It is expressed in pounds of sttern per kilowatt hour (or in kilograms of steam per kilowaft hour).

2.5.1.3 GUARANTEED STEAM RAW The turbine generator set guaranteed steam rate is the

nitewhichwillnotbeexceededwhenthetiirbinegeneratar

tions. The steam rate shaii be stated in pounds per kilowatt hour based on kilowatt output measured at the generator taminalS. For separate exciters, the exciter losses shall be deducted h m the output kilowatt

nema-sm-24-1991-r2002

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