Electrical installation work: 6th

Preface .............................................................................................................................xi Mapping to City and Guilds 2330 Certificate in Electrotechnical Technology ...................... xiii CHAPTER 1 Basic Information and Calculations .......................................................... 1 Units ................................................................................................................................ 1 Indices .............................................................................................................................. 4 Self-Assessment Questions ................................................................................................. 6 Simple Algebra .................................................................................................................. 6 Formulae or Equations ....................................................................................................... 7 Manipulation or Transposition of Formulae......................................................................... 7 Self-Assessment Questions .............................................................................................. 11 The Theorem of Pythagoras ............................................................................................. 11 Basic Trigonometry ......................................................................................................... 13 Self-Assessment Questions .............................................................................................. 15 Areas and Volumes ................................................................................................. 15 CHAPTER 2 Electricity ............................................................................................ 17 Molecules and Atoms ...................................................................................................... 17 Potential Difference ......................................................................................................... 20 Electron Flow and Conventional Current Flow ................................................................... 20 Conductors and Insulators ............................................................................................... 21 Electrical Quantities ......................................................................................................... 21 Ohm’s Law ...................................................................................................................... 27 Electricity and the Human Body ...................................................................................... 29 Types and Sources of Supply ........................................................................................... 30 Voltage Bands ................................................................................................................. 30 Measuring Current and Voltage ........................................................................................ 30 Components of a Circuit .................................................................................................. 31 Self-Assessment Questions .............................................................................................. 32 CHAPTER 3 Resistance, Current and Voltage, Power and Energy .............................. 33 Resistance ...................................................................................................................... 33 Voltage Drop ................................................................................................................... 36 Power: Symbol, P ; Unit, Watt (W) .................................................................................... 46 Electrical Energy: Symbol, W ; Unit, kWh .......................................................................... 51 Self-Assessment Questions......................................................................................... 56 CHAPTER 4 Electromagnetism ................................................................................ 59 Magnetism ...................................................................................................................... 59 Electromagnetism ........................................................................................................... 60 Application of Magnetic Effects ........................................................................................ 64 Drawing the Waveform of an Alternating Quantity ............................................................. 70 Addition of Waveforms .................................................................................................... 70 Root-Mean-Square (r.m.s.) Value ..................................................................................... 71 v vi Average Value ................................................................................................................. 73 Three-Phase a.c. Generator ............................................................................................. 73 Inductance: Symbol, L ; Unit, Henry (H) ........................................................................... 74 Induced e.m.f. Due to Change in Flux ............................................................................. 75 Self-Inductance ............................................................................................................... 75 Mutual Inductance: Symbol, M ; Unit, Henry (H) .............................................................. 76 Time Constant: Symbol, T ................................................................................................ 77 Graphical Derivation of Current Growth Curve .................................................................. 78 Energy Stored in a Magnetic Field ................................................................................... 80 Inductance in a.c. Circuits ............................................................................................... 80 Resistance and Inductance in Series ( R–L Circuits) ......................................................... 82 Impedance: Symbol, Z ; Unit, Ohm ( ظ) ............................................................................ 83 Resistance and Inductance in Parallel ............................................................................. 85 Power in a.c. Circuits ...................................................................................................... 86 Transformers .................................................................................................................... 89 Self-Assessment Questions ............................................................................................... 93 CHAPTER 5 Capacitors and Capacitance .................................................................. 95 Capacitors ....................................................................................................................... 95 Capacitance: Symbol, C; Unit, Farad (F) .......................................................................... 96 Dimensions of Capacitors ................................................................................................ 97 Capacitors in Series ......................................................................................................... 97 Capacitors in Parallel ....................................................................................................... 98 Capacitors in d.c. Circuits ................................................................................................ 99 Capacitance in a.c. Circuits ........................................................................................... 100 Capacitive Reactance: Symbol, Xc ; Unit, Ohm ( ظ) ......................................................... 101 Resistance and Capacitance in Series ........................................................................... 102 Resistance and Capacitance in Parallel ......................................................................... 103 Working Voltage ............................................................................................................ 103 Applications of Capacitors ............................................................................................. 104 Self-Assessment Questions ............................................................................................ 104 CHAPTER 6 Resistance, Inductance and Capacitance in Installation Work ................... 105 PF Improvement ........................................................................................................... 111 Self-Assessment Questions ............................................................................................ 120 CHAPTER 7 Three-Phase Circuits ............................................................................121 Star and Delta Connections ........................................................................................... 121 Current and Voltage Distribution .................................................................................... 122 Measurement of Power in Three-Phase Systems ............................................................. 126 Self-Assessment Questions ............................................................................................ 128 CHAPTER 8 Motors and Generators ........................................................................129 Direct-Current Motors .................................................................................................... 129 The a.c. Motors ............................................................................................................. 140 Starters ......................................................................................................................... 149 Installing a Motor .......................................................................................................... 153 Fault Location and Repairs to a.c. Machines .................................................................. 157 Power Factor of a.c. Motors ........................................................................................... 157 Motor Ratings ............................................................................................................... 162 Self-Assessment Questions ............................................................................................ 166 CHAPTER 9 Cells and Batteries .................................................................................... 167 General Background ..................................................................................................... 167 The Primary Cell ........................................................................................................... 167 Contents The Secondary Cell ....................................................................................................... 168 Cell and Battery Circuits ................................................................................................ 174 Self-Assessment Questions ............................................................................................ 177 CHAPTER 10 Illumination and ELV Lighting ..............................................................179 Light Sources ................................................................................................................ 179 Calculation of Lighting Requirements ............................................................................. 189 Self-Assessment Questions ............................................................................................ 199 CHAPTER 11 Electricity, the Environment and the Community ....................................201 Environmental Effects of the Generation of Electricity ..................................................... 201 New Developments ....................................................................................................... 205 The Purpose and Function of the National Grid ............................................................. 206 Generation, Transmission and Distribution Systems ....................................................... 207 The Aesthetic Effects of the Siting of Generation and Transmission Plant ........................ 208 CHAPTER 12 Health and Safety ..............................................................................211 Safety Regulations .......................................................................................................... 211 The Health and Safety at Work Act 1974 ....................................................................... 213 Electricity at Work Regulations 1989 .............................................................................. 215 Personal Protective Equipment Regulations ................................................................... 217 Construction (Design and Management) Regulations ..................................................... 218 Control of Substances Hazardous to Health Regulations ................................................ 218 The Building Regulations .............................................................................................. 218 General Safety ............................................................................................................... 219 The Mechanics of Lifting and Handling .......................................................................... 221 Work, Load and Effort ..................................................................................................... 224 Access Equipment ........................................................................................................ 226 The Joining of Materials ................................................................................................. 231 Fire Safety ..................................................................................................................... 231 Electrical Safety ............................................................................................................. 233 First Aid ........................................................................................................................ 235 Electric Shock ................................................................................................................ 235 CHAPTER 13 The Electrical Contracting Industry ......................................................237 Sample Specification ...................................................................................................... 241 Cost of Materials and Systems ........................................................................................ 246 CHAPTER 14 Installation Materials and Tools ............................................................251 Cables ........................................................................................................................... 252 Jointing and Terminations ............................................................................................. 255 Plastics ......................................................................................................................... 261 Conduit ......................................................................................................................... 262 Trunking ....................................................................................................................... 268 Traywork ....................................................................................................................... 272 Fixing and Tools ............................................................................................................. 273 Comparison of Systems ................................................................................................. 278 Self-Assessment Questions ............................................................................................ 280 CHAPTER 15 Installation Circuits and Systems ..........................................................281 Lighting Circuits ............................................................................................................ 281 Lighting Layouts ............................................................................................................ 283 Power Circuits ............................................................................................................... 284 Space Heating Systems .................................................................................................. 287 Radiant or Direct Heating .............................................................................................. 287 Thermostats ................................................................................................................... 289 Contents vii viii Installation Systems ....................................................................................................... 291 Industrial Installations ................................................................................................... 292 Multi-Storey Commercial or Domestic Installations .......................................................... 292 Off-Peak Supplies ......................................................................................................... 297 Alarm and Emergency Systems ..................................................................................... 299 Call Systems ................................................................................................................. 303 Emergency Lighting Systems .......................................................................................... 303 Central Heating Systems ............................................................................................... 305 Extra-Low-Voltage Lighting ............................................................................................. 306 Choice of System .......................................................................................................... 309 Special Locations ........................................................................................................... 309 CHAPTER 16 Earthing and Bonding .........................................................................325 Earth: What It Is, and Why and How We Connect To It ................................................... 325 Earth Electrode Resistance ............................................................................................ 329 Earthing Systems .......................................................................................................... 331 Earth Fault Loop Impedence ......................................................................................... 334 Residual Current Devices .............................................................................................. 337 Requirements for RCD Protection ................................................................................... 339 Self-Assessment Questions ............................................................................................ 343 CHAPTER 17 Protection .........................................................................................345 Protection ..................................................................................................................... 345 Control .......................................................................................................................... 364 CHAPTER 18 Circuit and Design .............................................................................369 Design Procedure ......................................................................................................... 369 Design Current .............................................................................................................. 370 Nominal Setting of Protection ........................................................................................ 370 Rating Factors ............................................................................................................... 370 Current-Carrying Capacity ............................................................................................. 372 Choice of Cable Size ...................................................................................................... 374 Voltage Drop ................................................................................................................. 375 Shock Risk ..................................................................................................................... 376 Thermal Constraints ....................................................................................................... 376 Selection of cpc Using Table 54.7 .................................................................................. 376 Installation Reference Methods ...................................................................................... 380 Installation Methods ....................................................................................................... 382 CHAPTER 19 Testing ..............................................................................................389 Measurement of Electrical Quantities .............................................................................. 389 Measurement of Current ............................................................................................... 391 Measurement of Voltage ................................................................................................ 394 Instruments in General .................................................................................................. 395 Selection of Test Instruments .......................................................................................... 396 Approved Test Lamps and Indicators ............................................................................. 397 Accidental RCD Operation ............................................................................................. 397 Calibration, Zeroing and Care of Instruments ................................................................. 398 Initial Inspection ............................................................................................................. 399 Testing Continuity of Protective Conductors..................................................................... 401 Testing Continuity of Ring Final Circuit Conductors ........................................................ 404 Testing Insulation Resistance ........................................................................................ 407 Special Tests ................................................................................................................. 409 Testing Polarity .............................................................................................................. 410 Contents ix Testing Earth Electrode Resistance ................................................................................ 411 Testing Earth Fault Loop Impedance .............................................................................. 413 External Loop Impedance Ze .......................................................................................... 415 Prospective Fault Current ............................................................................................... 417 Periodic Inspection ....................................................................................................... 418 Certification ................................................................................................................... 420 Inspection and Testing .................................................................................................. 421 Fault Finding ................................................................................................................. 425 CHAPTER 20 Basic Electronics Technology ..............................................................427 Electronics Components ................................................................................................ 427 Semi-Conductors .......................................................................................................... 430 Rectification .................................................................................................................. 431 Electronic Diagrams ...................................................................................................... 437 Electronics Assembly .................................................................................................... 439 Self-Assessment Questions ............................................................................................. 441 Answers to Self-Assessment Questions .......................................................................... 443 Index ............................................................................................................................ 449