Handbook of Electrical Engineering

Alan L. Sheldrake is the author of Handbook of Electrical Engineering: For Practitioners in the Oil, Gas and Petrochemical Industry, published by Wiley.

• Foreword xixPreface xxiAcknowledgements xxiiiAbout the Author xxv1 Estimation of Plant Electrical Load 11.1 Preliminary Single-Line Diagrams 11.2 Load Schedules 21.2.1 Worked example 51.3 Determination of Power Supply Capacity 81.4 Standby Capacity of Plain Cable Feeders and Transformer Feeders 121.5 Rating of Generators in Relation to their Prime Movers 131.5.1 Operation at low ambient temperatures 131.5.2 Upgrading of prime movers 131.6 Rating of Motors in Relation to their Driven Machines 131.7 Development of Single-Line Diagrams 141.7.1 The key single line diagram 151.7.2 Individual switchboards and motor control centres 151.8 Coordination with other Disciplines 161.8.1 Process engineers 161.8.2 Mechanical engineers 171.8.3 Instrument engineers 171.8.4 Communication and safety engineers 181.8.5 Facilities and operations engineers 18Reference 182 Gas Turbine Driven Generators 192.1 Classification of Gas Turbine Engines 192.1.1 Aero-derivative gas turbines 192.1.2 Light industrial gas turbines 202.1.3 Heavy industrial gas turbines 202.1.4 Single and two-shaft gas turbines 202.1.5 Fuel for gas turbines 232.2 Energy Obtained from a Gas Turbine 232.2.1 Effect of an inefficient compressor and turbine 292.2.2 Maximum work done on the generator 302.2.3 Variation of specific heat 312.2.4 Effect of ducting pressure drop and combustion chamber pressure drop 322.2.5 Heat rate and fuel consumption 352.3 Power Output from a Gas Turbine 362.3.1 Mechanical and electrical power losses 372.3.2 Factors to be considered at the design stage of a power plant 372.4 Starting Methods for Gas Turbines 392.5 Speed Governing of Gas Turbines 392.5.1 Open-loop speed-torque characteristic 392.5.2 Closed-loop speed-power characteristic 412.5.3 Governing systems for gas turbines 432.5.4 Load sharing between droop-governed gas turbines 442.5.5 Load sharing controllers 502.6 Mathematical Modelling of Gas Turbine Speed Governing Systems 522.6.1 Modern practice 522.6.2 Typical parameter values for speed governing systems 59References 59Further Reading 593 Synchronous Generators and Motors 613.1 Common Aspects Between Generators and Motors 613.2 Simplified Theory of Operation of a Generator 613.2.1 Steady state armature reaction 623.2.2 Transient state armature reaction 633.2.3 Sub-transient state armature reaction 633.3 Phasor Diagram of Voltages and Currents 643.4 The Derived Reactances 653.4.1 Sensitivity of X md , X a , X f and X kd to Changes in Physical dimensions 673.5 Active and Reactive Power Delivered from a Generator 683.5.1 A general case 683.5.2 The particular case of a salient pole generator 703.5.3 A simpler case of a salient pole generator 713.6 The Power Versus Angle Chart of a Salient Pole Generator 723.7 Choice of Voltages for Generators 733.8 Typical Parameters of Generators 733.9 Construction Features of High Voltage Generators and Induction Motors 783.9.1 Enclosure 783.9.2 Reactances 793.9.3 Stator windings 793.9.4 Terminal boxes 803.9.5 Cooling methods 803.9.6 Bearings 80References 814 Automatic Voltage Regulation 834.1 Modern Practice 834.1.1 Measurement circuits 834.1.2 Error sensing circuit 844.1.3 Power amplifier 844.1.4 Main exciter 884.2 IEEE Standard AVR Models 894.2.1 Worked example 924.2.2 Worked example 924.2.3 Determining of saturation constants 934.2.4 Typical parameter values for AVR systems 97Reference 975 Induction Motors 995.1 Principle of Operation of the Three-Phase Motor 995.2 Essential Characteristics 1005.2.1 Motor torque versus speed characteristic 1005.2.2 Motor starting current versus speed characteristic 1075.2.3 Load torque versus speed characteristic 1085.2.4 Sensitivity of characteristics to changes in resistances and reactances 1095.2.5 Worked example 1095.2.6 Typical impedance data for two-pole and four-pole induction motors 1145.2.7 Representing the deep-bar effect by two parallel branches 1145.3 Construction of Induction Motors 1195.4 Derating Factors 1215.5 Matching the Motor Rating to the Driven Machine Rating 1215.6 Effect of the Supply Voltage on Ratings 1225.7 Effect of the System Fault Level 1235.8 Cable Volt-drop Considerations 1235.9 Critical Times for Motors 1255.10 Methods of Starting Induction Motors 1255.10.1 Star-delta method 1265.10.2 Korndorfer auto-transformer method 1265.10.3 Soft-start power electronics method 1275.10.4 Series reactor method 1285.10.5 Part winding method 129References 1296 Transformers 1316.1 Operating Principles 1316.2 Efficiency of a Transformer 1346.3 Regulation of a Transformer 1356.4 Three-Phase Transformer Winding Arrangements 1366.5 Construction of Transformers 1376.5.1 Conservator and sealed type tanks 1396.6 Transformer Inrush Current 140References 1427 Switchgear and Motor Control Centres 1437.1 Terminology in Common Use 1437.2 Construction 1447.2.1 Main busbars 1447.2.2 Earthing busbars 1467.2.3 Incoming and busbar section switching device 1467.2.4 Forms of separation 1477.2.5 Ambient temperature derating factor 1497.2.6 Rated normal current 1497.2.7 Fault making peak current 1497.2.8 Fundamental AC part 1507.2.9 DC part 1507.2.10 Double frequency AC part 1507.2.11 Fault breaking current 1527.2.12 Fault withstand duty 1537.3 Switching Devices 1547.3.1 Outgoing switching device for switchgear 1547.3.2 Outgoing switching device for motor control centres 1557.4 Fuses for Motor Control Centre Outgoing Circuits 1567.5 Safety Interlocking Devices 1577.6 Control and Indication Devices 1587.6.1 Restarting and reaccelerating of motors 1587.6.2 Micro-computer based systems 1597.7 Moulded Case Circuit Breakers 1627.7.1 Comparison with fuses 1627.7.2 Operating characteristics 1637.7.3 Cut-off current versus prospective current 1647.7.4 i-squared-t characteristic 1647.7.5 Complete and partial coordination of cascaded circuit breakers 1657.7.6 Worked example for coordination of cascaded circuit breakers 1677.7.7 Cost and economics 172References 1728 Fuses 1738.1 General Comments 1738.2 Operation of a Fuse 1748.3 Influence of the Circuit X-to-R Ratio 1748.4 The I 2 t Characteristic 1768.4.1 Worked example 179References 1819 Cables, Wires and Cable Installation Practices 1839.1 Electrically Conducting Materials used in the Construction of Cables 1839.1.1 Copper and aluminium 1849.1.2 Tin 1849.1.3 Phosphor bronze 1859.1.4 Galvanised steel 1859.1.5 Lead 1869.2 Electrically Non-Conducting Materials used in the Construction of Cables 1879.2.1 Definition of basic terminology 1879.3 Composition of Power and Control Cables 1919.3.1 Compositional notation 1929.3.2 Conductor 1929.3.3 Conductor semiconducting screen 1969.3.4 Insulation 1969.3.5 Insulation semiconductor screen 1979.3.6 Inner sheath 1979.3.7 Lead sheathing 1979.3.8 Armouring 1989.3.9 Outer sheath 1989.4 Current Ratings of Power Cables 1989.4.1 Continuous load current 1989.4.2 Continuous rated current of a cable 1999.4.3 Volt-drop within a cable 2099.4.4 Protection against overloading current 2429.5 Cables with Enhanced Performance 2449.5.1 Fire retardance 2449.5.2 Fire resistance 2459.5.3 Emission of toxic gases and smoke 2459.5.4 Application of fire retardant and fire resistant cables 246Reference 24710 Hazardous Area Classification and the Selection of Equipment 24910.1 Historical Developments 24910.2 Present Situation 24910.3 Elements of Hazardous Area Classification 25110.3.1 Mixtures of gases, vapours and air 25110.4 Hazardous Area Zones 25310.4.1 Non-hazardous area 25310.4.2 Zone 2 hazardous area 25310.4.3 Zone 1 hazardous area 25310.4.4 Zone 0 hazardous area 25410.4.5 Adjacent hazardous zones 25410.5 Types of Protection for Hazardous Areas 25410.5.1 Type of protection ‘d’ 25510.5.2 Type of protection ‘e’ 25610.5.3 Type of protection ‘i’ 25610.5.4 Type of protection ‘m’ 25710.5.5 Type of protection ‘n’ and ‘n’ 25710.5.6 Type of protection ‘o’ 25810.5.7 Type of protection ‘p’ 25810.5.8 Type of protection ‘q’ 25910.5.9 Type of protection ‘s’ 25910.5.10 Type of protection ‘de’ 25910.6 Types of Protection for Ingress of Water and Solid Particles 26010.6.1 European practice 26010.6.2 American practice 26110.7 Certification of Hazardous Area Equipment 26510.8 Marking of Equipment Nameplates 266References 266Further Reading 26611 Fault Calculations and Stability Studies 26911.1 Introduction 26911.2 Constant Voltage Source – High Voltage 26911.3 Constant Voltage Source – Low Voltage 27111.4 Non-Constant Voltage Sources – All Voltage Levels 27311.5 Calculation of Fault Current due to Faults at the Terminals of a Generator 27411.5.1 Pre-fault or initial conditions 27411.5.2 Calculation of fault current – RMS symmetrical values 27611.6 Calculate the Sub-Transient symmetrical RMS Fault Current Contributions 27911.6.1 Calculate the sub-transient peak fault current contributions 28111.7 Application of the Doubling Factor to Fault Current I′′frms  found in 11.6 28711.7.1 Worked example 28811.7.2 Breaking duty current 29111.8 Computer Programs for Calculating Fault Currents 29211.8.1 Calculation of fault current – RMS and peak asymmetrical values 29211.8.2 Simplest case 29311.8.3 The circuit x-to-r ratio is known 29311.8.4 Detailed generator data is available 29311.8.5 Motor contribution to fault currents 29311.9 The use of Reactors 29411.9.1 Worked example 29711.10 Some Comments on the Application of IEC60363 and IEC 60909 30011.11 Stability Studies 30011.11.1 Steady state stability 30111.11.2 Transient stability 303References 308Further Reading 30912 Protective Relay Coordination 31112.1 Introduction to Overcurrent Coordination 31112.1.1 Relay notation 31312.2 Generator Protection 31312.2.1 Main generators 31312.2.2 Overcurrent 31412.2.3 Differential stator current relay 31812.2.4 Field failure relay 31912.2.5 Reverse active power relay 32112.2.6 Negative phase sequence relay 32212.2.7 Stator earth fault relays 32212.2.8 Over terminal voltage 32412.2.9 Under terminal voltage 32412.2.10 Under- and overfrequency 32512.3 Emergency Diesel Generators 32512.4 Feeder Transformer Protection 32612.4.1 Overcurrent 32912.4.2 High-set or instantaneous current 33012.4.3 Characteristics of the upstream source 33212.5 Feeder Cable Protection 33212.5.1 Overcurrent protection 33212.5.2 Short-circuit protection 33312.5.3 Earth fault protection 33312.6 Busbar Protection in Switchboards 33412.6.1 Busbar zone protection 33412.6.2 Overcurrent protection 33512.6.3 Undervoltage protection 33512.7 High Voltage Induction Motor Protection 33612.7.1 Overloading or thermal image 33712.7.2 Instantaneous or high-set overcurrent 33912.7.3 Negative phase sequence 33912.7.4 Core balance earth fault 34012.7.5 Differential stator current 34012.7.6 Stalling current 34012.7.7 Limitation to the number of successive starts 34112.7.8 Undercurrent 34112.7.9 High winding temperature 34212.7.10 High bearing temperature 34212.7.11 Excessive vibration 34212.8 Low Voltage Induction Motor Protection 34212.8.1 Overloading or thermal image 34312.8.2 Instantaneous or high-set overcurrent 34412.8.3 Negative phase sequence 34412.8.4 Core balance earth fault 34512.8.5 Stalling current 34512.8.6 Limitation to the number of successive starts 34512.9 Low Voltage Static Load Protection 34512.9.1 Time-delayed overcurrent 34612.9.2 Instantaneous or high-set overcurrent 34612.9.3 Core balance earth fault 34612.10 Mathematical Equations for Representing Standard, Very and Extremely Inverse Relays 346References 34913 Earthing and Screening 35113.1 Purpose of Earthing 35113.1.1 Electric shock 35113.1.2 Damage to equipment 35313.1.3 Zero reference potential 35313.2 Site Locations 35313.2.1 Steel structures 35413.2.2 Land-based plants 35413.2.3 Concrete and brick-built structures 35613.3 Design of Earthing Systems 35613.3.1 High voltage systems 35613.3.2 Low voltage three-phase systems 35713.3.3 IEC types of earthing systems 36013.3.4 Earth loop impedance 36513.3.5 Earthing rods and grids 36713.4 Construction Details Relating to Earthing 37113.4.1 Frames, casings and cubicle steelwork 37113.4.2 Screwed and clearance hole entries 37113.4.3 Earthing only one end of a cable 37213.5 Screening and Earthing of Cables used in Electronic Circuits 37313.5.1 Capacitance and inductance mechanisms 37313.5.2 Screening against external interference 37413.5.3 Earthing of screens 37913.5.4 Screening of high frequencies 38013.5.5 Power earths, cubicle and clean earths 381References 38314 Variable Speed Electrical Drivers 38514.1 Introduction 38514.1.1 Environment 38614.1.2 Power supply 38614.1.3 Economics 38714.2 Group 1 Methods 38814.2.1 Simple variable voltage supplies 38814.2.2 Pole-changing of the stator winding 38914.2.3 Pole amplitude modulated motors 39014.2.4 Wound rotor induction motors 39114.3 Group 2 Methods 39214.3.1 Variable voltage constant frequency supply 39214.3.2 Variable frequency variable voltage supply 39214.4 Variable Speed DC Motors 39414.5 Electrical Submersible Pumps 39414.5.1 Introduction 39414.5.2 Electrical submersible pump construction 39514.6 Control Systems for AC Motors 397References 40015 Harmonic Voltages and Currents 40115.1 Introduction 40115.2 Rectifiers 40215.2.1 Diode bridges 40215.2.2 Thyristor bridges 40415.2.3 Power transistor bridges 40715.2.4 DC motors 40715.3 Harmonic Content of the Supply Side Currents 41315.3.1 Simplified waveform of a six-pulse bridge 41315.3.2 Simplified commutation delay 41415.3.3 Fourier coefficients of the line current waveform 41415.3.4 Simplified waveform of a 12-pulse bridge 41715.4 Inverters 42115.4.1 Basic method of operation 42115.4.2 Three-phase power inversion 42215.4.3 Induction motor fed from a voltage source inverter 42315.5 Filtering of Power Line Harmonics 42915.6 Protection, Alarms and Indication 433References 43316 Computer Based Power Management Systems 43516.1 Introduction 43516.2 Typical Configurations 43516.3 Main Functions 43616.3.1 High-speed load shedding 43616.3.2 Load shedding priority table 43916.3.3 Low-speed load shedding 44016.3.4 Inhibiting the starting of large motors 44116.3.5 VDU display of one-line diagrams 44216.3.6 Active power sharing for generators 44316.3.7 Isochronous control of system frequency 44316.3.8 Reactive power sharing for generators 44416.3.9 Isochronous control of busbar voltage 44416.3.10 Condition monitoring of the gas turbines 44416.3.11 Scheduling the starting up and shutting down of the main generators 44516.3.12 Control of the reacceleration of motor loads 44616.3.13 Auto-synchronising of the main generators 44716.3.14 Data logging, archiving, trending display, alarms, messages and status reporting 44817 Uninterruptible Power Supplies 44917.1 AC Uninterruptible Power Supplies 44917.1.1 The inverter 44917.1.2 Coordination of the sub-circuit rated current with the inverter rated current 45017.1.3 Earth fault leakage detection 45117.2 DC Uninterruptible Power Supplies 45117.2.1 UPS battery chargers 45217.2.2 Batteries 45517.3 Redundancy Configurations 457References 45818 Miscellaneous Subjects 45918.1 Lighting Systems 45918.1.1 Types of lighting fittings 46118.1.2 Levels of illumination 46118.2 Navigation Aids 46318.2.1 Flashing marker lights 46318.2.2 White and red flashing lights 46418.2.3 Navigation buoys 46518.2.4 Identification panels 46518.2.5 Aircraft hazard lighting 46518.2.6 Helicopter landing facilities 46618.2.7 Radar 46618.2.8 Radio direction-finder 46618.2.9 Sonar devices 46718.3 Cathodic Protection 467References 46819 Preparing Equipment Specifications 46919.1 The Purpose of Specifications 46919.2 A Typical Format for a Specification 47019.2.1 Introduction 47119.2.2 Scope of supply 47119.2.3 Service and environmental conditions 47119.2.4 Compliant international standards 47119.2.5 Definition of technical and non-technical terms 47119.2.6 Performance or functional requirements 47219.2.7 Design and construction requirements 47319.2.8 Inspection and testing 47419.2.9 Spare parts 47519.2.10 Documentation 47519.2.11 Appendices 47720 Summary of the Generalised Theory of Electrical Machines as Applied to Synchronous Generators and Induction Motors 47920.1 Introduction 47920.2 Synchronous Generator 48020.2.1 Basic mathematical transformations 48320.3 Some Notes on Induction Motors 49020.3.1 Derived reactances 49120.3.2 Application of three-phase short circuit 49120.3.3 Derived reactances and time constants for an induction motor 49320.3.4 Derivation of an equivalent circuit 49520.3.5 ‘Re-iteration or recapitulation’ 49620.3.6 Contribution of three-phase short-circuit current from induction motor 501References 504Further Reading 505Appendix A Abbreviations Commonly used in Electrical Documents 507Appendix B A List of Standards Often Used for Designing Electrical Systems and for Specifying Equipment 517B. 1 International Electro-technical Commission (Europe) 517B. 2 Institute of Petroleum (UK) 525B. 3 International Standards Organisation (Worldwide) 526B. 4 British Standards Institution (UK) 526B. 5 American Petroleum Institute (USA) 530B. 6 Counseil International des Grands Reseaux Electriques (France) 530B. 7 Engineering Equipment and Materials Users Association (UK) 530B. 8 Electricity Council (UK) 531B. 9 Verband Deutscher Electrechniker (Germany) 531B.10 Institute of Electronic and Electrical Engineers Inc. (USA) 531B.11 Miscellaneous References from the UK 532Appendix C Numbering System for Protective Devices, Control and Indication Devices for Power Systems 533C. 1 Application of Protective Relays, Control and Alarm Devices for Power System Circuits 533C.1.1 Notes to sub-section C. 1 535C. 2 Electrical Power System Device Numbers and Functions 536Appendix D Under-Frequency and Over-Temperature Protection of Gas-Turbine Driven Generators 539Appendix E List of Document Types to be Produced During a Project 545E. 1 Contractors Documents 546E.1.1 Feasibility studies 546E.1.2 Conceptual design 546E.1.3 Detail design 547E. 2 Manufacturers Documents 549E.2.1 Feasibility studies 549E.2.2 Conceptual design 549E.2.3 Detail design 549Appendix F Worked Example for Calculating the Performance of a Gas Turbine 551F. 1 The Requirements and Data Given 551F. 2 Basic Requirements 551F. 3 Detailed Requirements 552F. 4 Basic Solutions 552F. 5 Detailed Solutions 553Appendix G Worked Example for the Calculation of Volt-drop in a Circuit Containing an Induction Motor 559G.1 Introduction 559Appendix H Worked Example for the Calculation of Earthing Current and Electric Shock Hazard Potential Difference in a Rod and Grid Earthing System 585H.1 Worked Example 585Appendix I Conversion Factors for the SI System of Units 597I. 1 Fundamental SI Units 597I. 2 Derived Non-electrical Units 597I. 3 Derived Electrical Units 598I. 4 Conversions 598I.4. 1 Length 598I.4. 2 Area 599I.4. 3 Volume 599I.4.4 Mass and density 600I.4. 5 Velocity and acceleration 600I.4.6 Force 601I.4. 7 Torque 601I.4. 8 Power 601I.4. 9 Energy and work 601I.4.10 Pressure 602I.4.11 Moment of inertia and momentum 603I.4.12 Illumination 603I.4.13 Electricity and magnetism 604I.4.14 Miscellaneous quantities 604I. 5 International Standards Organisation (ISO) Conditions 605I. 6 Standard Temperature and Pressure (STP) Conditions 605I. 7 Regularly Used Constants 605I. 8 Regularly Used Prefixes 606I. 9 References 606Index 607

"...an excellent reference...with many worked out examples and loads of practical real world calculations, this well laid out book would be an invaluable guide for new power system engineers...and also provide experienced engineers a way to check their designs or find out about other areas." (IEEE Electrical Insulation Magazine, January/February 2004)