Systems controls embedded systems energy and machines

The Electrical Engineering HandbookThird Edition Systems, Controls, Embedded Systems, Energy, and Machines... The thirdedition has a new look and comprises six volumes including: Circuit

The Electrical Engineering Handbook

Third Edition

Systems, Controls, Embedded Systems, Energy, and Machines

The Electrical Engineering Handbook Series

Series Editor

Richard C Dorf

University of California, Davis

Titles Included in the Series

The Handbook of Ad Hoc Wireless Networks, Mohammad Ilyas

The Avionics Handbook, Cary R Spitzer

The Biomedical Engineering Handbook, Third Edition, Joseph D Bronzino

The Circuits and Filters Handbook, Second Edition, Wai-Kai Chen

The Communications Handbook, Second Edition, Jerry Gibson

The Computer Engineering Handbook, Vojin G Oklobdzija

The Control Handbook, William S Levine

The CRC Handbook of Engineering Tables, Richard C Dorf

The Digital Signal Processing Handbook, Vijay K Madisetti and Douglas Williams The Electrical Engineering Handbook, Third Edition, Richard C Dorf

The Electric Power Engineering Handbook, Leo L Grigsby

The Electronics Handbook, Second Edition, Jerry C Whitaker

The Engineering Handbook, Third Edition, Richard C Dorf

The Handbook of Formulas and Tables for Signal Processing, Alexander D Poularikas The Handbook of Nanoscience, Engineering, and Technology, William A Goddard, III,

Donald W Brenner, Sergey E Lyshevski, and Gerald J Iafrate

The Handbook of Optical Communication Networks, Mohammad Ilyas and

Hussein T Mouftah

The Industrial Electronics Handbook, J David Irwin

The Measurement, Instrumentation, and Sensors Handbook, John G Webster

The Mechanical Systems Design Handbook, Osita D.I Nwokah and Yidirim Hurmuzlu The Mechatronics Handbook, Robert H Bishop

The Mobile Communications Handbook, Second Edition, Jerry D Gibson

The Ocean Engineering Handbook, Ferial El-Hawary

The RF and Microwave Handbook, Mike Golio

The Technology Management Handbook, Richard C Dorf

The Transforms and Applications Handbook, Second Edition, Alexander D Poularikas The VLSI Handbook, Wai-Kai Chen

Sensors, Nanoscience, Biomedical Engineering,

and Instruments Broadcasting and Optical Communication Technology Computers, Software Engineering, and Digital Devices Systems, Controls, Embedded Systems, Energy,

and Machines

The Electrical Engineering Handbook

Third Edition

Systems, Controls, Embedded Systems, Energy, and Machines

Edited by

Richard C Dorf

University of California Davis, California, U.S.A.

A CRC title, part of the Taylor & Francis imprint, a member of the Taylor & Francis Group, the academic division of T&F Informa plc.

Boca Raton London New York

Published in 2006 by

CRC Press

Taylor & Francis Group

6000 Broken Sound Parkway NW, Suite 300

Boca Raton, FL 33487-2742

© 2006 by Taylor & Francis Group, LLC

CRC Press is an imprint of Taylor & Francis Group

No claim to original U.S Government works

Printed in the United States of America on acid-free paper

10 9 8 7 6 5 4 3 2 1

International Standard Book Number-10: 0-8493-7347-6 (Hardcover)

International Standard Book Number-13: 978-0-8493-7347-3 (Hardcover)

Library of Congress Card Number 2005054347

This book contains information obtained from authentic and highly regarded sources Reprinted material is quoted with permission, and sources are indicated A wide variety of references are listed Reasonable efforts have been made to publish reliable data and information, but the author and the publisher cannot assume responsibility for the validity of all materials

or for the consequences of their use.

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Library of Congress Cataloging-in-Publication Data

Systems, controls, embedded systems, energy, and machines / edited by Richard C Dorf.

p cm.

Includes bibliographical references and index.

ISBN 0-8493-7347-6 (alk paper)

1 Electric power systems Control 2 Electric power systems 3 Systems engineering I Dorf, Richard

Taylor & Francis Group

is the Academic Division of Informa plc.

Purpose

The purpose of The Electrical Engineering Handbook, 3rd Edition is to provide a ready reference for thepracticing engineer in industry, government, and academia, as well as aid students of engineering The thirdedition has a new look and comprises six volumes including:

Circuits, Signals, and Speech and Image Processing

Electronics, Power Electronics, Optoelectronics, Microwaves, Electromagnetics, and Radar

Sensors, Nanoscience, Biomedical Engineering, and Instruments

Broadcasting and Optical Communication Technology

Computers, Software Engineering, and Digital Devices

Systems, Controls, Embedded Systems, Energy, and Machines

Each volume is edited by Richard C Dorf and is a comprehensive format that encompasses the manyaspects of electrical engineering with articles from internationally recognized contributors The goal is toprovide the most up-to-date information in the classical fields of circuits, signal processing, electronics,electromagnetic fields, energy devices, systems, and electrical effects and devices, while covering the emergingfields of communications, nanotechnology, biometrics, digital devices, computer engineering, systems, andbiomedical engineering In addition, a complete compendium of information regarding physical, chemical,and materials data, as well as widely inclusive information on mathematics, is included in each volume Manyarticles from this volume and the other five volumes have been completely revised or updated to fit the needs

of today, and many new chapters have been added

The purpose of Systems, Controls, Embedded Systems, Energy, and Machines is to provide a ready reference tosubjects in the fields of energy devices, machines, and systems, as well as control systems and embeddedsystems Here we provide the basic information for understanding these fields We also provide informationabout the emerging fields of embedded systems

Locating Your Topic

Numerous avenues of access to information are provided A complete table of contents is presented at thefront of the book In addition, an individual table of contents precedes each of the sections Finally, eachchapter begins with its own table of contents The reader should look over these tables of contents to becomefamiliar with the structure, organization and content of the book For example, see Section I: Energy, then

Two indexes have been compiled to provide multiple means of accessing information: a subject index and

an index of contributing authors The subject index can also be used to locate key definitions The page onwhich the definition appears for each key (defining) term is clearly identified in the subject index

The Electrical Engineering Handbook, 3rd Edition is designed to provide answers to most inquiries and directthe inquirer to further sources and references We hope that this volume will be referred to often and thatinformational requirements will be satisfied effectively

Acknowledgments

This volume is testimony to the dedication of the Board of Advisors, the publishers, and my editorialassociates I particularly wish to acknowledge at Taylor and Francis Nora Konopka, Publisher; HelenaRedshaw, Editorial Project Development Manager; and Mimi Williams, Project Editor Finally, I am indebted

to the support of Elizabeth Spangenberger, Editorial Assistant

Richard C Dorf

Editor-in-Chief

Richard C Dorf,Professor of Electrical and Computer Engineering at the University of California, Davis,teaches graduate and undergraduate courses in electrical engineering in the fields of circuits and controlsystems He earned a Ph.D in electrical engineering from the U.S Naval Postgraduate School, an M.S fromthe University of Colorado, and a B.S from Clarkson University Highly concerned with the discipline ofelectrical engineering and its wide value to social and economic needs, he has written and lecturedinternationally on the contributions and advances in electrical engineering

Professor Dorf has extensive experience with education and industry and is professionally active in the fields

of robotics, automation, electric circuits, and communications He has served as a visiting professor at theUniversity of Edinburgh, Scotland; the Massachusetts Institute of Technology; Stanford University; and theUniversity of California, Berkeley

Professor Dorf is a Fellow of The Institute of Electrical and Electronics Engineers and a Fellow of theAmerican Society for Engineering Education Dr Dorf is widely known to the profession for his ModernControl Systems, 10th Edition (Addison-Wesley, 2004) and The International Encyclopedia of Robotics (Wiley,1988) Dr Dorf is also the co-author of Circuits, Devices and Systems (with Ralph Smith), 5th Edition (Wiley,1992), and Electric Circuits, 7th Edition (Wiley, 2006) He is also the author of Technology Ventures (McGraw-Hill, 2005) and The Engineering Handbook, 2nd Edition (CRC Press, 2005)

State University of New York

Binghamton, New York

Banmali Rawat

University of NevadaReno, Nevada

Richard S Sandige

California PolytechnicState UniversitySan Luis Obispo, California

Leonard Shaw

Polytechnic UniversityBrooklyn, New York

Braden Allenby

AT&T Environment, Health & Safety

Bedminster, New Jersey

Leo Grigsby

Auburn University Jacksons Gap, Alabama

Charles A Gross

Auburn University Auburn, Alabama

Hodge E Jenkins

Mercer University Macon, Georgia

Thomas R Kurfess

Clemson University Clemson, South Carolina

Ty A Lasky

University of California, Davis Davis, California

Berkeley, California

Gordon K.F Lee

San Diego State University

San Diego, California

Cornelius T Leondes

University of California

San Diego, California

Thomas R Mancini

Sandia National Laboratories

Albuquerque, New Mexico

Florida Atlantic University

Boca Raton, Florida

Timisoara, Romania

V.P Shmerko

University of Calgary Alberta, Canada

Tom Short

EPRI Solutions, Inc.

Schenectady, New York

East Lansing, Michigan

Alvin M Strauss

Vanderbilt University Nashville, Tennessee

Ronald J Tallarida

Temple University Philadelphia, Pennsylvania

Vyacheslav Tuzlukov

Ajou University Suwon, South Korea

Darlusz Ucin´ski

University of Zielona Gora, Poland

S.N Yanushkevich

University of Calgary Alberta, Canada

Won-Sik Yoon

Ajou University Suwon, South Korea

SECTION I Energy

1 Conventional Power Generation George G Karady 1-1

2 Alternative Power Systems and Devices

2.1 Distributed Power Johan H.R Enslin and Rama Ramakumar 2-12.2 Solar Electric Systems Thomas R Mancini, Roger Messenger, and Jerry Ventre 2-132.3 Fuel Cells Gregor Hoogers 2-20

3 Transmissions

3.1 High-Voltage Direct-Current Transmission Rao S Thallam 3-13.2 Compensation Mohamed E El-Hawary 3-173.3 Fault Analysis in Power Systems Charles A Gross 3-273.4 Protection Arun G Phadke 3-443.5 Transient Operation of Power Systems R.B Gungor 3-533.6 Planning J Duncan Glover 3-61

4 Power Quality Jos Arrillaga 4-1

5 Power System Analysis Andrew Hanson and Leo Grigsby 5-1

6 Power Transformers Charles A Gross 6-1

7 Energy Distribution George G Karady and Tom Short 7-1

8 Electrical Machines

8.1 Generators Ioan Serban 8-18.2 Motors Mehdi Ferdowsi 8-218.3 Small Electric Motors Elias G Strangas 8-32

9 Energy Management K Neil Stanton, Jay C Giri, and Anjan Bose 9-1

10 Power System Analysis Software C.P Arnold and N.R Watson 10-1

SECTION II Systems

11 Control Systems

11.1 Models William L Brogan 11-111.2 Dynamic Response Gordon K.F Lee 11-8

11.5 Compensation Charles L Phillips and Royce D Harbor 11-5811.6 Digital Control Systems Raymond G Jacquot and John E McInroy 11-6611.7 Nonlinear Control Systems Derek P Atherton 11-72

12 Navigation Systems Myron Kayton 12-1

13 Environmental Effects Karen Blades, Braden Allenby, and Michele M Blazek 13-1

17 Welding and Bonding George E Cook, Reginald Crawford, David R DeLapp, and

Alvin M Strauss 17-1

18 Human–Computer Interaction Evelyn P Rozanski and Anne R Haake 18-1

19 Decision Diagram Technique S.N Yanushkevich and V.P Shmerko 19-1

20 Vehicular Systems Linda Sue Boehmer 20-1

SECTION III Mathematics, Symbols, and Physical Constants

Introduction Ronald J Tallarida III-1Greek Alphabet III-3International System of Units (SI) III-3Conversion Constants and Multipliers III-6Physical Constants III-8Symbols and Terminology for Physical and Chemical Quantities III-9Credits III-13Probability for Electrical and Computer Engineers Charles W Therrien III-14

Indexes

Author Index A-1

Subject Index S-1

Energy

1 Conventional Power Generation G.G Karady 1-1

Introduction * Fossil Power Plants * Gas Turbine and Combined-Cycle Power Plants *

Nuclear Power Plants * Geothermal Power Plants * Hydroelectric Power Plants

2 Alternative Power Systems and Devices J.H.R Enslin, R Ramakumar,

T.R Mancini, R Messenger, J Ventre, G Hoogers 2-1

Distributed Power * Solar Electric Systems * Fuel Cells

3 Transmissions R.S Thallam, M.E El-Hawary, C.A Gross, A.G Phadke,

R.B Gungor, J.D Glover 3-1

High-Voltage Direct-Current Transmission * Compensation * Fault Analysis in Power Systems *

Protection * Transient Operation of Power Systems * Planning

4 Power Quality J Arrillaga 4-1

Power Quality Disturbances * Power Quality Monitoring * Power Quality Conditioning

5 Power System Analysis A Hanson, L Grigsby 5-1

Introduction * Types of Power System Analysis * The Power Flow Problem * Formulation of

the Bus Admittance Matrix * Example Formulation of the Power Flow Equations * Bus

Classifications * Generalized Power Flow Development * Solution Methods * Component

Power Flows

6 Power Transformers C.A Gross 6-1

Transformer Construction * Power Transformer Modeling * Transformer Performance *

Transformers in Three-Phase Connections * Autotransformers

7 Energy Distribution G.G Karady, T Short 7-1

Introduction * Primary Distribution System * Secondary Distribution System * Radial

Distribution System * Secondary Networks * Load Characteristics * Voltage Regulation *

Capacitors and Voltage Regulators * Distribution System Hardware * Overhead versus

Underground * Faults * Short-Circuit Protection * Reliability and Power Quality * Grounding

8 Electrical Machines I Serban, M Ferdowsi, E.G Strangas 8-1

Generators * Motors * Small Electric Motors

9 Energy Management K.N Stanton, J.C Giri, A Bose 9-1

Introduction * Power System Data Acquisition and Control * Automatic Generation Control *

Distribution System Management * Energy Management * Security Control * Operator Training Simulator

10 Power System Analysis Software C.P Arnold, N.R Watson 10-1

Introduction * Early Analysis Programs * The Second Generation of Programs * Conclusions

I-1

Fuel Handling * Boiler * Fuel System * Air-Flue Gas System *

Water-Steam System * Turbine * Generator * Electric System *

Condenser * Stack and Ash Handling * Cooling and Feedwater System

1.3 Gas-Turbine and Combined-Cycle Power Plants 1-11

Gas Turbine * Combined-Cycle Plant

1.4 Nuclear Power Plants 1-12

Pressurized-Water Reactor * Boiling-Water Reactor

1.5 Geothermal Power Plants 1-14

Hydrothermal Source * Petrothermal Source * Geopressured Source

1.6 Hydroelectric Power Plants 1-15

High-Head Plants * Low- and Medium-Head Plants *

Hydrogenerators

The electric energy demand of the world is continuously increasing, and most of the energy is generated byconventional power plants, which remain the only cost-effective method for generating large quantities ofenergy

Power plants utilize energy stored in the Earth and convert it to electrical energy that is distributed and used

by customers This process converts most of the energy into heat, thus increasing the entropy of the Earth Inthis sense, power plants deplete the Earth’s energy supply Efficient operation becomes increasingly important

1882 The boilers were developed from heating furnaces Oil was the preferred and most widely used fuel in thebeginning The oil shortage promoted coal-fired plants, but the adverse environmental effects (sulfur dioxidegeneration, acid rain, dust pollution, etc.) curtailed their use in the late 1970s Presently the most acceptablefuel is natural gas, which minimizes pollution and is available in large quantities The increasing peak loaddemand led to the development of gas turbine power plants These units can be started or stopped within a

1-1

few minutes The latest development is the combined-cycle power plant, which combines a gas turbine and athermal unit The hot exhaust gas from the gas turbine generates steam to drive a steam turbine, or the hot gas

is used as the source of hot combustion air in a boiler, which provides steam to drive a turbine During thenext two decades, gas-fired power plants will dominate the electric industry

The hydro plants’ ancestors are water wheels used for pumping stations, mill driving, etc Water-driventurbines were developed in the last century and have been used for generation of electricity since the beginning

of their commercial use However, most of the sites that can be developed economically are currently beingutilized No significant new development is expected in the United States in the near future

Nuclear power plants appeared after the Second World War The major development occurred during the1960s; however, by the 1980s environmental considerations stopped plant development in the United Statesand slowed it down all over the world Presently, the future of nuclear power generation is unclear, but theabundance of nuclear fuel and the expected energy shortage in the early part of the next century mayrejuvenate nuclear development if safety issues can be resolved

Geothermal power plants are the product of the clean energy concept, although the small-scale, localapplication of geothermal energy has a long history Presently only a few plants are in operation The potentialfor further development is limited because of the unavailability of geothermal energy sites that can bedeveloped economically

Typical technical data for different power plants is shown in Table 1.1

The operational concept and major components of a fossil power plant are shown in Figure 1.1

Boiler

Two types of boilers are used in modern power plants: the subcritical water-tube drum-type and thesupercritical once-through type The former operates around 2500 psi, which is under the water criticalpressure of 3208.2 psi The latter operates above that pressure, at around 3500 psi The superheated steamtemperature is about 1000–F (540–C) because of turbine temperature limitations

A typical subcritical water-tube drum-type boiler has an inverted U shape On the bottom of the rising part

is the furnace where the fuel is burned The walls of the furnace are covered by water pipes The drum and thesuperheater are at the top of the boiler The falling part of the U houses the reheaters, economizer (waterheater), and air preheater, which is supplied by the forced-draft fan The induced-draft fan forces the flue gasesout of the system and sends them up the stack located behind the boiler A flow diagram of the drum-typeboiler is shown in Figure 1.2 The steam generator has three major systems: fuel, air-flue gas, and water-steam

Fuel System

Fuel is mixed with air and injected into the furnace through burners The burners are equipped with nozzlesthat are supplied by preheated air and carefully designed to assure the optimum air-fuel mix The fuel mix isignited by oil or gas torches The furnace temperature is around 3000–F

TABLE 1.1 Power Plant Technical Data

Generation Type MW SizeTypical

Capitalized Plant Cost,

$/kW

Construction Lead Time, Years Heat Rate,Btu/kWh Fuel Cost,$/MBtu Fuel Type Equivalent ForcedOutage Rate

Equivalent Scheduled Outage Rate O & M Fixed,$/kW/year Cost Variable,$/MWh

Air-Flue Gas System

Ambient air is driven by the forced-draft fan through the air preheater which is heated by the temperature (600–F) flue gases The air is mixed with fuel in the burners and enters the furnace, where itsupports the fuel burning The hot combustion flue gas generates steam and flows through the boiler to heatthe superheater, reheaters, economizer, etc Induced-draft fans, located between the boiler and the stack,increase the flow and send the 300–F flue gases to the atmosphere through the stack

high-Water-Steam System

Large pumps drive the feedwater through the high-pressure heaters and the economizer, which furtherincreases the water temperature (400 to 500–F) The former is heated by steam removed from the turbine;the latter is heated by the flue gases The preheated water is fed to the steam drum Insulated tubes, calleddowncomers, are located outside the furnace and lead the water to a header The header distributes thehot water among the risers These are water tubes that line the furnace walls The water tubes are heated

FIGURE 1.2 Flow diagram of a typical drum-type steam boiler (Source: M.M El-Wakil, Power Plant Technology, New York: McGraw-Hill, 1984, p 210 With permission.)

FIGURE 1.1 Major components of a fossil power plant.

by the combustion gases through both convection and

radiation The steam generated in these tubes flows to

the drum, where it is separated from the water

Circulation is maintained by the density difference

between the water in the downcomer and the water

tubes Saturated steam, collected in the drum, flows

through the superheater The superheater increases the

steam temperature to about 1000–F Dry superheated

steam drives the high-pressure turbine The exhaust

from the high-pressure turbine goes to the reheater,

which again increases the steam temperature The

reheated steam drives the low-pressure turbine

The typical supercritical once-through-type boiler

concept is shown in Figure 1.3

The feedwater enters through the economizer to the

boiler consisting of riser tubes that line the furnace wall

All the water is converted to steam and fed directly to the superheater The latter increases thesteam temperature above the critical temperature of the water and drives the turbine The construction

of these steam generators is more expensive than the drum-type units but has a higher operating efficiency.Figure 1.4 shows an approximate layout and components of a coal-fired power plant The solid arrows showthe flow of flue gas The dotted arrows show the airflow through the preheating system The figure shows theapproximate location of the components

Turbine

The turbine converts the heat energy of the steam into mechanical energy Modern power plants usuallyuse one high-pressure and one or two lower-pressure turbines A typical turbine arrangement is shown inFigure 1.5

The figure shows that only one bearing is between each of the machines The shafts are connected to form atandem compound steam-turbine unit High-pressure steam enters the high-pressure turbine to flow throughand drive the turbine The exhaust is reheated in the boiler and returned to the lower-pressure units Both therotor and the stationary part of the turbine have blades The length of the blades increases from the steamentrance to the exhaust

Figure 1.6 shows the blade arrangement of an impulse-type turbine Steam enters through nozzles and flowsthrough the first set of moving rotor blades The following stationary blades change the direction of the flowand direct the steam into the next set of moving blades The nozzles increase the steam speed and reducepressure, as shown in the figure The impact of the high-speed steam, generated by the change of direction andspeed in the moving blades, drives the turbine

The reaction-type turbine has nonsymmetrical blades, which assure that the pressure continually dropsthrough all rows of blades but that steam velocity decreases in the moving blades and increases in thestationary blades

Figure 1.7 shows the rotor of a large steam turbine The figure shows that the diameters of the blades vary.The high-pressure steam enters at the middle (the low blade diameter side) of the turbine As the high-pressure steam passes through the blades its pressure decreases In order to maintain approximately constantdriving force, the blades’ diameter is increased towards the end of the turbine

Generator

The generator converts mechanical energy from the turbines into electrical energy The major components

of the generator are the frame, stator core and winding, rotor and winding, bearings, and cooling system.Figure 1.8 shows the cross section of a modern hydrogen-cooled generator

FIGURE 1.3 Concept of once-through-type steam generator.

1-5Conventional Power Generation

The stator has a laminated and slotted silicon steel iron core The stacked core is clamped andheld together by insulated axial through bolts The stator winding is placed in the slots and consists of

a copper-strand configuration with woven glass insulation between the strands and mica flakes, mica

FIGURE 1.4 Major components and physical layout of a coal-fired fossil power plant (Source: A.W Culp, Principles of Energy Conversion, 2nd ed., New York: McGraw Hill, 1991, p 220 With permission.)

mat, or mica paper wall insulation To avoid insulation damage caused by vibration, the wall insulation is reinforced by asphalt, epoxy-impregnated fiberglass, or Dacron The largest machinestator is Y-connected and has two coils per phase, connected in parallel Most frequently, the stator ishydrogen cooled; however, small units may be air cooled and very large units may be water cooled.The solid steel rotor has slots milled along the axis The multiturn, copper rotor winding is placed in theslots and cooled by hydrogen Cooling is enhanced by subslots and axial cooling passages The rotor winding isrestrained by wedges inserted in the slots.

ground-The rotor winding is supplied by dc current, either directly by a brushless excitation system or throughcollector rings The rotor is supported by bearings at both ends The nondrive-end bearing is insulated toavoid shaft current generated by stray magnetic fields The hydrogen is cooled by a hydrogen-to-water heatexchanger mounted on the generator or installed in a closed-loop cooling system

FIGURE 1.5 Open large tandem compound steam turbine (Courtesy of Toshiba.)

1-7Conventional Power Generation

The dc current of the rotor generates a rotating

magnetic field that induces an ac voltage in the stator

winding This voltage drives current through the load

and supplies the electrical energy

Figure 1.9 shows the typical arrangement of a turbine,

generator, and exciter installed in a power plant The

figure shows that the three units are connected in series

The turbine has a high- and low-pressure stage and

drives the generator The generator drives the exciter

that produces the dc current for the generator rotor

Electric System

Energy generated by the power plant supplies the electric

network through transmission lines The power plant

operation requires auxiliary power to operate mills,

pumps, etc The auxiliary power requirement is

approximately 10 to 15%

Smaller generators are directly connected in parallel

using a busbar Each generator is protected by a circuit breaker The power plant auxiliary system is suppliedfrom the same busbar The transmission lines are connected to the generator bus, either directly or through atransformer

The larger generators are unit-connected In this arrangement the generator is directly connected, without

a circuit breaker, to the main transformer A conceptual one-line diagram is shown in Figure 1.10 Thegenerator supplies main and auxiliary transformers without circuit breakers The units are connected inparallel at the high-voltage side of the main transformers by a busbar The transmission lines are alsosupplied from this bus Circuit breakers are installed at the secondary side of the main and auxiliarytransformer The application of a generator circuit breaker is not economical in the case of large generators.Because of the generator’s large short-circuit current, special expensive circuit breakers are required.However, the transformers reduce the short-circuit current and permit the use of standard circuit breakers

FIGURE 1.6 Velocity and pressure variation in an impulse turbine.

FIGURE 1.7 Rotor of a large steam turbine (Courtesy of Siemens.)

FIGURE 1.8 Direct hydrogen-inner-cooled generator (Source: R.W Beckwith, Westinghouse Power Systems Marketing Training Guide on Large Electric Generators, Pittsburgh: Westinghouse Electric Corp., 1979, p 54 With permission.)

FIGURE 1.9 Turbine, generator, and exciter (Courtesy of Siemens.)

1-9Conventional Power Generation

at the secondary side The disconnect switches permit visual observation of the off state and are needed formaintenance of the circuit breakers.

Condenser

The condenser condenses turbine exhaust steam to water, which is pumped back to the steam generatorthrough various water heaters The condensation produces a vacuum necessary to exhaust the steam from theturbine The condenser is a shell-and-tube heat exchanger, where steam condenses on water-cooled tubes.Cold water is obtained from the cooling towers or other cooling systems The condensed water is fed through adeaerator, which removes absorbed gases from the water Next, the gas-free water is mixed with the feedwaterand returned to the boiler The gases absorbed in the water may cause corrosion (oxygen) and increasecondenser pressure, adversely affecting efficiency Older plants use a separate deaerator heater, while deaerators

in modern plants are usually integrated in the condenser, where injected steam jets produce pressure drop andremove absorbed gases

Stack and Ash Handling

The stack is designed to disperse gases into the atmosphere without disturbing the environment This requiressufficient stack height to assist the fans in removing gases from the boiler through natural convection Thegases contain both solid particles and harmful chemicals Solid particles, like dust, are removed from the fluegas by electrostatic precipitators or baghouse filters Harmful sulfur dioxide is eliminated by scrubbers Themost common is the lime/limestone scrubbing process

Coal-fired power plants generate a significant amount of ash The disposition of the ash causesenvironmental problems Several systems have been developed in past decades Large ash particles are collected

by a water-filled ash hopper located at the bottom of the furnace Fly ash is removed by filters, then mixedwith water Both systems produce sludge that is pumped to a clay-lined pond where water evaporates and theash fills disposal sites The clay lining prevents intrusion of groundwater into the pond

Cooling and Feedwater System

The condenser is cooled by cold water The open-loop system obtains the water from a river or sea, if thepower plant location permits it The closed-loop system utilizes cooling towers, spray ponds, or spray canals

In the case of spray ponds or canals, the water is pumped through nozzles which generate fine sprays.Evaporation cools the water sprays as they fall back into the pond Several different types of cooling towershave been developed The most frequently used is the wet cooling tower, where the hot water is sprayed on top

of a latticework of horizontal bars The water drifts downward and is cooled through evaporation by the airwhich is forced through by fans or natural updraft

FIGURE 1.10 Conceptual one-line diagram for a unit-connected generator.

The power plant loses a small fraction of the water through leakage The feedwater system replaces this lostwater Replacement water has to be free from absorbed gases, chemicals, etc because the impurities causesevere corrosion in the turbines and boiler The water-treatment system purifies replacement water bypretreatment, which includes filtering, chlorination, demineralization, condensation, and polishing Thesecomplicated chemical processes result in a corrosion-free high-quality feedwater.

The plant contains a gas turbine and a conventional steam turbine The hot exhaust gas from the gas turbinesupplies a heat exchanger to generate steam The steam drives a convectional turbine and generator The steamcondenses in the condenser, which is cooled by water from a cooling tower or fresh water from a lake or river.The combined-cycle power plant has higher efficiency (around 42%) than a conventional plant (27 to 32%) or

a gas-turbine power plant The capacity of this plant is 100 to 500 MW

More than 500 nuclear power plants operate around the world Close to 300 operate pressurized water reactors(PWRs); more than 100 are built with boiling-water reactors (BWRs); about 50 use gas-cooled reactors; andthe rest are heavy-water reactors In addition a few fast-breeder reactors are in operation These reactorsare built for better utilization of uranium fuel The modern nuclear plant size varies from 100 to 1300 MW.Figure 1.13 shows the large Paulo Verde nuclear power plant in Arizona The 4000-MW-capacity power planthas three 1300-MW pressurized-water reactors, The figure shows the large concrete domes housing the nuclearreactors, the cooling towers, generator building, and the large switchyard

Pressurized-Water Reactor

The general arrangement of a power plant with a PWR is shown in Figure 1.14(a)

The reactor heats the water from about 550 to about 650–F High pressure, at about 2235 psi, preventsboiling Pressure is maintained by a pressurizer, and the water is circulated by a pump through a heatexchanger The heat exchanger evaporates the feedwater and generates steam that supplies a system similar to a

FIGURE 1.12 Combined-cycle power plant.

conventional power plant The advantage of this two-loop system is the separation of the potentiallyradioactive reactor cooling fluid from the water-steam system.

The reactor core consists of fuel and control rods Grids hold both the control and fuel rods The fuel rodsare inserted in the grid following a predetermined pattern The fuel elements are zircaloy-clad rods filledwith UO2 pellets The control rods are made of a silver (80%), cadmium (5%), and indium (15%) alloyprotected by stainless steel The reactor operation is controlled by the position of the rods In addition,control rods are used to shut down the reactor The rods are released and fall into the core when emergencyshutdown is required Cooling water enters the reactor from the bottom, flows through the core, and isheated by nuclear fission

Boiling-Water Reactor

In the BWR shown in Figure 1.14(b), the pressure is low, about 1000 psi The nuclear reaction heats the waterdirectly to evaporate it and produce wet steam at about 545–F The remaining water is recirculated and mixedwith feedwater The steam drives a turbine that typically rotates at 1800 rpm The rest of the plant is similar to

a conventional power plant A typical reactor arrangement is shown in Figure 1.15 The figure shows all themajor components of a reactor The fuel and control rod assembly is located in the lower part The steamseparators are above the core, and the steam dryers are at the top of the reactor The reactor is enclosed by aconcrete dome

FIGURE 1.14 (a) Power plant with PWR; (b) power plant with BWR.

FIGURE 1.13 View of Palo Verde nuclear power plant (Courtesy of Salt River Project.)

1-13Conventional Power Generation

1.5 Geothermal Power Plants

The solid crust of the Earth is an average of 20 miles (32 km) deep Under the solid crust is a molten mass,the magma The heat stored in the magma is the source of geothermal energy The hot molten magmacomes close to the surface at certain points in the Earth and produces volcanoes, hot springs, and geysers.These are the signs of a possible geothermal site Three forms of geothermal energy are considered fordevelopment

Hydrothermal Source

This is the most developed source Power plants, up to a capacity of 2000 MW, are in operation worldwide.Heat from the magma is conducted upward by the rocks The groundwater drifts down through the cracksand fissures to form reservoirs when water-impermeable solid rockbed is present The water in thisreservoir is heated by the heat from the magma Depending on the distance from the magma and rockconfiguration, steam, hot pressurized water, or a mixture of the two is generated Signs of these underwaterreservoirs include hot springs and geysers The reservoir is tapped by a well, which brings the steam-watermixture to the surface to produce energy The geothermal power plant concept is illustrated in Figure 1.16The hot water and steam mixture is fed into a separator If the steam content is high, a centrifugalseparator is used to remove the water and other particles The obtained steam drives a turbine The typicalpressure is around 100 psi, and the temperature is around 400–F (200–C) If the water content is high, the

FIGURE 1.15 Typical BWR reactor arrangement (Source: Courtesy of General Electric Company.)

water-steam mixture is led through a flashed-steam system where the expansion generates a better quality ofsteam and separates the steam from the water The water is returned to the ground, and the steam drives theturbine Typically the steam entering the turbine has a temperature of 120 to 150–C and a pressure of 30 to

40 psi

The turbine drives a conventional generator The typical rating is in the 20- to 100-MW range The exhauststeam is condensed in a direct-contact condenser A part of the obtained water is reinjected into the ground.The rest of the water is fed into a cooling tower to provide cold water to the condenser

Major problems with geothermal power plants are the minerals and noncondensable gases in thewater The minerals make the water highly corrosive, and the separated gases cause air pollution Anadditional problem is noise pollution The centrifugal separator and blowdowns require noise dampersand silencers

Petrothermal Source

Some fields have only hot rocks under the surface Utilization of this petrothermal source requires pumpingsurface water through a well in a constructed hole to a reservoir The hot water is then recovered throughanother well The problem is the formation of a reservoir The U.S government is studying practical uses ofpetrothermal sources

Geopressured Source

In deep underground holes (8,000 to 30,000 ft) a mixture of pressurized water and natural gas, like methane,may sometimes be found These geopressured sources promise power generation through the combustion ofmethane and the direct recovery of heat from the water The geopressured method is currently in anexperimental stage, with operating pilot plants

Hydroelectric power plants convert energy produced by a water head into electric energy A typicalhydroelectric power plant arrangement is shown in Figure 1.17

The head is produced by building a dam across a river, which forms the upper-level reservoir In the case oflow head, the water forming the reservoir is fed to the turbine through the intake channel or the turbine isintegrated in the dam The latter arrangement is shown in Figure 1.17(a) Penstock tubes or tunnels are used

FIGURE 1.16 Concept of a geothermal power plant.

1-15Conventional Power Generation

for medium- (Figure 1.17(b)) and high-head plants (Figure 1.18) The spillway regulates the excess water byopening gates at the bottom of the dam or permitting overflow on the spillway section of the dam The waterdischarged from the turbine flows to the lower or tail-water reservoir, which is usually a continuation of theoriginal water channel.

FIGURE 1.17 Hydroelectric power plant arrangement (a) Low-head plant, (b) medium-head plant (Source: D.G Fink, Standard Handbook for Electrical Engineers, New York: McGraw-Hill, 1978 With permission.)

FIGURE 1.18 Hydroelectric power plant arrangement, high-head plant (Source: D.G Fink, Standard Handbook for Electrical Engineers, New York: McGraw-Hill, 1978 With permission.)

Low- and Medium-Head Plants

Low- and medium-head installations (Figure 1.17) are built with reaction-type turbines, where the waterpressure is mostly converted to velocity in the turbine The two basic classes of reaction turbines are thepropeller or Kaplan type, mostly used for low-head plants, and the Francis type, mostly used for medium-headplants The cross section of a typical low-head Kaplan turbine is shown in Figure 1.20

The vertical-shaft turbine and generator are supported by a thrust bearing immersed in oil The generator is

in the upper, watertight chamber The turbine runner has four to ten propeller types and adjustable pitchblades The blades are regulated from 5 to 35– by an oil-pressure-operated servomechanism The water isevenly distributed along the periphery of the runner by a concrete spiral case and regulated by adjustablewicket blades The water is discharged from the turbine through an elbow-shaped draft tube The conicalprofile of the tube reduces the water speed from the discharge speed of 10 to 30 ft/s to 1 ft/s to increase turbineefficiency

FIGURE 1.19 Aerial view of Roosevelt Dam and hydropower plant (36 MW) in Arizona (Courtesy of Salt River Project.)

1-17Conventional Power Generation

The hydrogenerator is a low-speed (100 to 360 rpm) salient-pole machine with a vertical shaft A typicalnumber of poles is from 20 to 72 They are mounted on a pole spider, which is a welded, spoked wheel Thespider is mounted on the forged steel shaft The poles are built with a laminated iron core and strandedcopper winding Damper bars are built in the pole faces The stator is built with a slotted, laminated ironcore that is supported by a welded steel frame Windings are made of stranded conductors insulatedbetween the turns by glass fiber or Dacron glass The ground insulation is multiple layers of mica tapeimpregnated by epoxy or polyester resins The older machines use asphalt and mica-tape insulation, which issensitive to corona-discharge-caused insulation deterioration Direct water cooling is used for very largemachines, while the smaller ones are air- or hydrogen-cooled Some machines use forced-air cooling with anair-to-water heat exchanger A braking system is installed in larger machines to stop the generator rapidlyand to avoid damage to the thrust

FIGURE 1.20 Typical low-head hydroplant with Kaplan turbine (Courtesy of Hydro-Que`bec.)

Superheater: A heat exchanger that increases the steam temperature to about 1000–F It is heated by theflue gases.

Surge tank: An empty vessel that is located at the top of the penstock It is used to store water surge whenthe turbine valve is suddenly closed

References

A.J Ellis, ‘‘Using geothermal energy for power,’’ Power, vol 123, no 10, 1979

M.M El-Wakil, Power Plant Technology, New York: McGraw-Hill, 1984

A.V Nero, A Guidebook to Nuclear Reactors, Berkeley: University of California Press Ltd., 1979

J Weisman and L.E Eckart, Modern Power Plant Engineering, Englewood Cliffs, N.J.: Prentice-Hall, 1985

Further Information

Other recommended publications include the ‘‘Power Plant Electrical References Series,’’ published by EPRI,which consists of several books dealing with power plant electrical system design A good source ofinformation on the latest developments is Power magazine, which regularly publishes articles on powerplants

Additional books include the following:

S Glasstone and M.C Edlund, The Elements of Nuclear Reactor Theory, New York: Van Nostrand, 1952, p 416

G Murphy, Elements of Nuclear Engineering, New York: Wiley, 1961

M.A Schultz, Control of Nuclear Reactors and Power Plants, New York: McGraw-Hill, 1955

R.H Shannon, Handbook of Coal-Based Electric Power Generation, Park Ridge, N.J.: Noyes, 1982, p 372.E.J.G Singer, Combustion: Fossil Power Systems, Windsor, Conn.: Combustion Engineering, Inc., 1981.B.G.A Skrotzki and W.A Vopat, Power Station Engineering and Economy, New York: McGraw-Hill, 1960.M.J Steinberg and T.H Smith, Economy Loading of Power Plants and Electric Systems, New York: Wiley, 1943,

Alternative Power Systems and Devices

Thermoelectrics * Thermionics * Energy Storage * Network Impacts

2.2 Solar Electric Systems 2-13

Solar Thermal Electric Systems * Photovoltaic Power Systems

Distributed power (DP) refers to the process and concepts in which small to medium (a few kW up to 50 MW

or more) power generation facilities, energy storage facilities (thermal, flywheel, hydro, flow, and regularbatteries), and other strategies are located at or near the customer’s loads and premises DP technologiesinstalled near customers’ loads operate as grid-connected or islanded resources at the distribution orsubtransmission level and are geographically scattered throughout the service area DP generation harnessesrenewable and nonrenewable energy sources, such as solar insolation, wind, biomass, tides, hydro, waves,geothermal, biogas, natural gas, hydrogen, and diesel, in a distributed manner DP also includes severalnonutility sources of electricity, including facilities for self-generation, energy storage, and combined heat andpower (CHP) or cogeneration systems

Interest in DP has been growing steadily, due to inherently high reliability and possible efficiencyimprovements over conventional generation In addition to the obvious advantages realized by thedevelopment of renewable energy sources, DP is ideally suited to power sensitive loads, small remote loadslocated far from the grid, and integrated renewable energy sources into the grid

To interface these different power concepts, electrical networks are currently evolving into hybrid networks,including ac and dc, with energy storage for individual households, office buildings, industry, and utility feeders

2-1