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Handbook of Electrical Engineering

631 Pages · 2006 · 3.84 MB · English

  • Handbook of Electrical Engineering

    Handbook of


    Electrical Engineering


    HandbookofElectricalEngineering:ForPractitionersintheOil,GasandPetrochemicalIndustry. AlanL.Sheldrake


    uf6d92003JohnWiley&Sons,Ltd ISBN:0-471-49631-6 Handbook of


    Electrical Engineering


    For Practitioners in the Oil, Gas and


    Petrochemical Industry


    Alan L. Sheldrake


    Consulting Electrical Engineer, Bangalore, India Copyrightuf6d92003 JohnWiley&SonsLtd,TheAtrium,SouthernGate,Chichester,


    WestSussexPO198SQ,England


    Telephone(+44)1243779777


    Email(forordersandcustomerserviceenquiries):cs-books@wiley.co.uk


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    LibraryofCongressCataloging-in-PublicationData


    Sheldrake,AlanL.


    Handbookofelectricalengineering:forpractitionersintheoil,gas,andpetrochemical


    industry/AlanL.Sheldrake.


    p.cm.


    Includesbibliographicalreferencesandindex.


    ISBN0-471-49631-6(alk.paper)


    1.Electricmachinery–Handbooks,manuals,etc.2.Petroleumengineering–Equipment


    andsupplies–Handbooks,manuals,etc.I.Title.


    TK2000.S522003


    621.31(cid:1)042–dc21


    2002192434


    BritishLibraryCataloguinginPublicationData


    AcataloguerecordforthisbookisavailablefromtheBritishLibrary


    ISBN0-471-49631-6


    Typesetin10/12ptTimesbyLaserwordsPrivateLimited,Chennai,India


    PrintedandboundinGreatBritainbyAntonyRoweLtd,Chippenham,Wiltshire


    Thisbookisprintedonacid-freepaperresponsiblymanufacturedfromsustainableforestry


    inwhichatleasttwotreesareplantedforeachoneusedforpaperproduction. This book is dedicated to my dear wife Ilse who with great patience


    encouraged me to persevere with the completion of this work. Contents


    Foreword xix


    Preface xxi


    Acknowledgements xxiii


    About the Author xxv


    1 Estimation of Plant Electrical Load 1


    1.1 Preliminary Single-Line Diagrams 1


    1.2 Load Schedules 2


    1.2.1 Worked example 5


    1.3 Determination of Power Supply Capacity 8


    1.4 Standby Capacity of Plain Cable Feeders and Transformer Feeders 12


    1.5 Rating of Generators in Relation to their Prime Movers 13


    1.5.1 Operation at low ambient temperatures 13


    1.5.2 Upgrading of prime movers 13


    1.6 Rating of Motors in Relation to their Driven Machines 13


    1.7 Development of Single-Line Diagrams 14


    1.7.1 The key single line diagram 15


    1.7.2 Individual switchboards and motor control centres 15


    1.8 Coordination with other Disciplines 16


    1.8.1 Process engineers 16


    1.8.2 Mechanical engineers 17


    1.8.3 Instrument engineers 17


    1.8.4 Communication and safety engineers 18


    1.8.5 Facilities and operations engineers 18


    Reference 18


    2 Gas Turbine Driven Generators 19


    2.1 Classification of Gas Turbine Engines 19


    2.1.1 Aero-derivative gas turbines 19


    2.1.2 Light industrial gas turbines 20


    2.1.3 Heavy industrial gas turbines 20


    2.1.4 Single and two-shaft gas turbines 20


    2.1.5 Fuel for gas turbines 23


    2.2 Energy Obtained from a Gas Turbine 23


    2.2.1 Effect of an inefficient compressor and turbine 29


    2.2.2 Maximum work done on the generator 30 viii


    2.2.3 Variation of specific heat 31


    2.2.4 Effect of ducting pressure drop and combustion chamber


    pressure drop 32


    2.2.5 Heat rate and fuel consumption 35


    2.3 Power Output from a Gas Turbine 36


    2.3.1 Mechanical and electrical power losses 37


    2.3.2 Factors to be considered at the design stage of a power plant 37


    2.4 Starting Methods for Gas Turbines 39


    2.5 Speed Governing of Gas Turbines 39


    2.5.1 Open-loop speed-torque characteristic 39


    2.5.2 Closed-loop speed-power characteristic 41


    2.5.3 Governing systems for gas turbines 43


    2.5.4 Load sharing between droop-governed gas turbines 44


    2.5.5 Load sharing controllers 50


    2.6 Mathematical Modelling of Gas Turbine Speed Governing Systems 52


    2.6.1 Modern practice 52


    2.6.2 Typical parameter values for speed governing systems 59


    References 59


    Further Reading 59


    3 Synchronous Generators and Motors 61


    3.1 Common Aspects Between Generators and Motors 61


    3.2 Simplified Theory of Operation of a Generator 61


    3.2.1 Steady state armature reaction 62


    3.2.2 Transient state armature reaction 63


    3.2.3 Sub-transient state armature reaction 63


    3.3 Phasor Diagram of Voltages and Currents 64


    3.4 The Derived Reactances 65


    3.4.1 Sensitivity of xmd, xa, xf and xkd to changes in physical


    dimensions 67


    3.5 Active and Reactive Power Delivered from a Generator 68


    3.5.1 A general case 68


    3.5.2 The particular case of a salient pole generator 70


    3.5.3 A simpler case of a salient pole generator 71


    3.6 The Power Versus Angle Chart of a Salient Pole Generator 72


    3.7 Choice of Voltages for Generators 73


    3.8 Typical Parameters of Generators 73


    3.9 Construction Features of High Voltage Generators and Induction Motors 78


    3.9.1 Enclosure 78


    3.9.2 Reactances 79


    3.9.3 Stator windings 79


    3.9.4 Terminal boxes 80


    3.9.5 Cooling methods 80


    3.9.6 Bearings 80


    References 81 ix


    4 Automatic Voltage Regulation 83


    4.1 Modern Practice 83


    4.1.1 Measurement circuits 83


    4.1.2 Error sensing circuit 84


    4.1.3 Power amplifier 84


    4.1.4 Main exciter 88


    4.2 IEEE Standard AVR Models 89


    4.2.1 Worked example 92


    4.2.2 Worked example 92


    4.2.3 Determining of saturation constants 93


    4.2.4 Typical parameter values for AVR systems 97


    Reference 97


    5 Induction Motors 99


    5.1 Principle of Operation of the Three-Phase Motor 99


    5.2 Essential Characteristics 100


    5.2.1 Motor torque versus speed characteristic 100


    5.2.2 Motor starting current versus speed characteristic 107


    5.2.3 Load torque versus speed characteristic 108


    5.2.4 Sensitivity of characteristics to changes in resistances and reactances 109


    5.2.5 Worked example 109


    5.2.6 Typical impedance data for two-pole and four-pole induction motors 114


    5.2.7 Representing the deep-bar effect by two parallel branches 114


    5.3 Construction of Induction Motors 119


    5.4 Derating Factors 121


    5.5 Matching the Motor Rating to the Driven Machine Rating 121


    5.6 Effect of the Supply Voltage on Ratings 122


    5.7 Effect of the System Fault Level 123


    5.8 Cable Volt-drop Considerations 123


    5.9 Critical Times for Motors 125


    5.10 Methods of Starting Induction Motors 125


    5.10.1 Star-delta method 126


    5.10.2 Korndorfer auto-transformer method 126


    5.10.3 Soft-start power electronics method 127


    5.10.4 Series reactor method 128


    5.10.5 Part winding method 129


    References 129


    6 Transformers 131


    6.1 Operating Principles 131


    6.2 Efficiency of a Transformer 134


    6.3 Regulation of a Transformer 135


    6.4 Three-Phase Transformer Winding Arrangements 136


    6.5 Construction of Transformers 137


    6.5.1 Conservator and sealed type tanks 139 x


    6.6 Transformer Inrush Current 140


    References 142


    7 Switchgear and Motor Control Centres 143


    7.1 Terminology in Common Use 143


    7.2 Construction 144


    7.2.1 Main busbars 144


    7.2.2 Earthing busbars 146


    7.2.3 Incoming and busbar section switching device 146


    7.2.4 Forms of separation 147


    7.2.5 Ambient temperature derating factor 149


    7.2.6 Rated normal current 149


    7.2.7 Fault making peak current 149


    7.2.8 Fundamental AC part 150


    7.2.9 DC part 150


    7.2.10 Double frequency AC part 150


    7.2.11 Fault breaking current 152


    7.2.12 Fault withstand duty 153


    7.3 Switching Devices 154


    7.3.1 Outgoing switching device for switchgear 154


    7.3.2 Outgoing switching device for motor control centres 155


    7.4 Fuses for Motor Control Centre Outgoing Circuits 156


    7.5 Safety Interlocking Devices 157


    7.6 Control and Indication Devices 158


    7.6.1 Restarting and reaccelerating of motors 158


    7.6.2 Micro-computer based systems 159


    7.7 Moulded Case Circuit Breakers 162


    7.7.1 Comparison with fuses 162


    7.7.2 Operating characteristics 163


    7.7.3 Cut-off current versus prospective current 164


    7.7.4 i-squared-t characteristic 164


    7.7.5 Complete and partial coordination of cascaded circuit breakers 165


    7.7.6 Worked example for coordination of cascaded circuit breakers 167


    7.7.7 Cost and economics 172


    References 172


    8 Fuses 173


    8.1 General Comments 173


    8.2 Operation of a Fuse 174


    8.3 Influence of the Circuit X-to-R Ratio 174


    8.4 The I2t Characteristic 176


    8.4.1 Worked example 179


    References 181 xi


    9 Cables, Wires and Cable Installation Practices 183


    9.1 Electrically Conducting Materials used in the Construction of Cables 183


    9.1.1 Copper and aluminium 184


    9.1.2 Tin 184


    9.1.3 Phosphor bronze 185


    9.1.4 Galvanised steel 185


    9.1.5 Lead 186


    9.2 Electrically Non-Conducting Materials used in the Construction of


    Cables 187


    9.2.1 Definition of basic terminology 187


    9.3 Composition of Power and Control Cables 191


    9.3.1 Compositional notation 192


    9.3.2 Conductor 192


    9.3.3 Conductor semiconducting screen 196


    9.3.4 Insulation 196


    9.3.5 Insulation semiconductor screen 197


    9.3.6 Inner sheath 197


    9.3.7 Lead sheathing 197


    9.3.8 Armouring 198


    9.3.9 Outer sheath 198


    9.4 Current Ratings of Power Cables 198


    9.4.1 Continuous load current 198


    9.4.2 Continuous rated current of a cable 199


    9.4.3 Volt-drop within a cable 209


    9.4.4 Protection against overloading current 242


    9.5 Cables with Enhanced Performance 244


    9.5.1 Fire retardance 244


    9.5.2 Fire resistance 245


    9.5.3 Emission of toxic gases and smoke 245


    9.5.4 Application of fire retardant and fire resistant cables 246


    Reference 247


    10 Hazardous Area Classification and the Selection of Equipment 249


    10.1 Historical Developments 249


    10.2 Present Situation 249


    10.3 Elements of Hazardous Area Classification 251


    10.3.1 Mixtures of gases, vapours and air 251


    10.4 Hazardous Area Zones 253


    10.4.1 Non-hazardous area 253


    10.4.2 Zone 2 hazardous area 253


    10.4.3 Zone 1 hazardous area 253


    10.4.4 Zone 0 hazardous area 254


    10.4.5 Adjacent hazardous zones 254 xii


    10.5 Types of Protection for Hazardous Areas 254


    10.5.1 Type of protection ‘d’ 255


    10.5.2 Type of protection ‘e’ 256


    10.5.3 Type of protection ‘i’ 256


    10.5.4 Type of protection ‘m’ 257


    10.5.5 Type of protection ‘n’ and ‘n’ 257


    10.5.6 Type of protection ‘o’ 258


    10.5.7 Type of protection ‘p’ 258


    10.5.8 Type of protection ‘q’ 259


    10.5.9 Type of protection ‘s’ 259


    10.5.10 Type of protection ‘de’ 259


    10.6 Types of Protection for Ingress of Water and Solid Particles 260


    10.6.1 European practice 260


    10.6.2 American practice 261


    10.7 Certification of Hazardous Area Equipment 265


    10.8 Marking of Equipment Nameplates 266


    References 266


    Further Reading 266


    11 Fault Calculations and Stability Studies 269


    11.1 Introduction 269


    11.2 Constant Voltage Source – High Voltage 269


    11.3 Constant Voltage Source – Low Voltage 271


    11.4 Non-Constant Voltage Sources – All Voltage Levels 273


    11.5 Calculation of Fault Current due to Faults at the Terminals of a Generator 274


    11.5.1 Pre-fault or initial conditions 274


    11.5.2 Calculation of fault current – rms symmetrical values 276


    11.6 Calculate the Sub-Transient symmetrical RMS Fault Current Contributions 279


    11.6.1 Calculate the sub-transient peak fault current contributions 281


    11.7 Application of the Doubling Factor to Fault Current I(cid:1)(cid:1) found in 11.6 287


    frms


    11.7.1 Worked example 288


    11.7.2 Breaking duty current 291


    11.8 Computer Programs for Calculating Fault Currents 292


    11.8.1 Calculation of fault current – rms and peak asymmetrical values 292


    11.8.2 Simplest case 293


    11.8.3 The circuit x-to-r ratio is known 293


    11.8.4 Detailed generator data is available 293


    11.8.5 Motor contribution to fault currents 293


    11.9 The use of Reactors 294


    11.9.1 Worked example 297


    11.10 Some Comments on the Application of IEC60363 and IEC60909 300


    11.11 Stability Studies 300


    11.11.1 Steady state stability 301


    11.11.2 Transient stability 303


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