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| موضوع: كتاب An Introduction to Safety Grounding الإثنين 11 ديسمبر 2023, 6:47 am | |
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أخواني في الله أحضرت لكم كتاب An Introduction to Safety Grounding Asser A. Zaky
و المحتوى كما يلي :
Contents Preface .ix Chapter 1 Effect of Current on the Human Body .1 1.1 Introduction .1 1.2 Effect of Electric Shock on Human Beings .3 1.3 Effect of Current Duration 4 1.4 The Electric Resistance of the Human Body 5 Chapter 2 Resistance to Ground .7 2.1 Resistance to Ground of a Hemisphere .7 2.2 Measurement of Electrode Resistance to Ground . 11 2.3 Soil Resistivity . 16 2.4 Measurement of Soil Resistivity 18 2.4.1 Simple Box Method 18 2.4.2 Wenner Method 19 2.4.3 Electromagnetic Induction Method 20 2.5 Computer Programs .22 Chapter 3 Earthing Electrodes 23 3.1 Single Driven Rod .23 3.2 Grounding Using Multiple Rods .25 3.3 Grounding Using Horizontally Buried Wires .30 3.4 Grounding Using Buried Plates . 32 3.5 Water Pipes or Steel Reinforcement as Grounding Electrodes 33 3.6 The Resistance Area 33 Chapter 4 Step, Touch, and Transfer Voltages 35 4.1 Step Voltage . 35 4.2 Touch Voltage 36 4.3 Transfer Touch Voltage 39 4.4 Grounding of Power Towers 40 4.4.1 Effect of Overhead Ground Wire on Tower Footing Resistance . 40 Chapter 5 Grounding Systems 45 5.1 Magnitude of Resistance to Ground 45 5.2 Elements of the Grounding System . 45vi Contents 5.2.1 The Area of Land . 47 5.2.1.1 Use of Chemical Salts . 47 5.2.1.2 Increasing the Soil’s Ability to Retain Water . 49 5.2.2 Ground Electrodes 50 5.2.2.1 Driven Rods 50 5.2.2.2 Concrete-Encased Electrodes . 52 5.2.2.3 Water and Gas Pipes . 53 5.2.2.4 Structural and Reinforcing Steel 54 5.2.2.5 Equipotential Bonding 54 5.2.3 Connections in Grounding Systems .54 5.2.4 Grounding Conductors .56 5.2.4.1 Size of Grounding Conductors . 57 5.2.4.2 Protective Sleeve .59 5.2.5 Ground Connection Provisions 60 5.2.6 Equipment Grounding Conductors 60 5.2.6.1 Conductor Size according to the Adiabatic Equation 61 5.2.6.2 Conductor Size According to USA Specifications (NFPA-70) 67 5.2.6.3 Metal Cable Trays as Grounding Conductors 68 5.2.6.4 Flexible Metal Conduits 71 5.2.6.5 Cable Sheath and Armor 72 5.2.6.6 Jumpers .72 5.3 Metallic Corrosion .72 5.4 General Rules for the Grounding of Branch Substations 74 5.5 Protective Grounding of Consumer Installations: Types of Grounding Systems 79 5.5.1 The TN-C System 80 5.5.2 The TT System .82 5.5.3 The TN-S System .84 5.5.4 Protective Multiple Earthing 87 5.5.5 The IT System 89 5.6 Protection by Isolation .90 5.7 Grounding of Computers and Data Processing Equipment 91 Chapter 6 Substation Grounding Systems 93 6.1 Introduction .93 6.2 Design Steps 94 6.2.1 Ground Mat Resistance 94 6.2.2 Calculation of Maximum GPR .97 6.2.3 Determination of Maximum Touch and Step Voltages 98Contents vii 6.2.4 Safety Requirements 102 6.3 Design of Ground Mat using Computer Program . 104 Chapter 7 Static Electrification . 111 7.1 Introduction . 111 7.2 Conditions Necessary for Ignition . 111 7.2.1 Explosion Limits 112 7.2.2 Oxygen . 114 7.2.3 Ignition Sources 114 7.2.4 Minimum Ignition Energy . 115 7.3 Generation of Electrostatic Charges 115 7.3.1 Contact Electrification between Solid Surfaces . 117 7.3.2 Static Electrification in Liquids and Gases 119 7.4 Ways for Reducing the Formation of Surface Charges .120 7.5 Electrostatic Induction . 122 7.6 Types of Electric Discharges . 122 7.6.1 The Spark or Arc Discharge . 123 7.6.2 Brush Discharges and Propagating Brush Discharges .127 7.6.3 Corona Discharges . 128 7.7 Methods of Controlling Electrostatic Charges 129 7.7.1 Grounding and Bonding . 129 7.7.2 Floors and Clothing for Static Control . 130 7.7.2.1 Static Conductive Floors . 131 7.7.2.2 Static Dissipative Floors . 131 7.7.3 Control of Humidity . 133 7.7.4 Ionization 134 Chapter 8 Protection against Lightning 137 8.1 Nature of Lightning . 137 8.2 Why Protect against Lightning 140 8.3 Lightning Protection System . 144 8.3.1 The Air Terminals 145 8.3.2 Mesh Air Termination Networks . 146 8.3.3 Down Conductors . 147 8.3.4 Types of Conductors . 149 8.3.5 Grounding 150 8.4 Inductance, Side Flashing, and Separation Distance 150 8.5 Zones of Protection . 153 8.6 Tanks and Stacks . 157 8.7 Protection of Transmission Lines by Aerial Ground Wires 157 8.7.1 Secondary Field of Ground Conductor 158 8.7.2 Height of Ground Conductor 161 8.8 Protection against Surges 161viii Contents Appendix A: Wire Sizes 163 Bibliography . 167 Index 169 Index adiabatic equation 61 aerial ground wire 157ff air terminals 145 air termination network 146 anodic index 73 apparent resistivity 20 arc discharge 123 area of land 47 atmospheric field 157 bentonite 49 bonding 129, 150 brazing 55 brush discharges 127 burial depth 9 buried plates 32 buried wire 30ff cable armor 60, 72 cable shield 60, 72 cable trays 68 capacitance, of human body 123, 124 chemical grounding rod 49 chemical salts 47 clamps 54, 149 clothing for esd 132 compression joint 56 computer center 91 concrete 33 encased electrodes 52 conductive floors 131 conductors down 146ff equipment grounding 47 grounding 55, 60 neutral 80ff protective 80ff cone of protection 146, 156 connections mechanical 54, 149 welded 55 contact electrification 111, 117 copperweld 50 corona discharge 128 active 129, 134 passive 129, 134 corrosion 72 current duration 4 physiological effects 3 danger triangle 112 depth of burial 9 discharges, types of arc 123 brush 127 corona 128 propagating brush 127 spark 123 dissipative floors 131, 132 double insulation 91 down conductor 147ff driven rod 23, 50 duration, current 4, 65 touch voltage 80 earth leakage breaker 83 electric shock 3 electrode hemisphere 7 plate 32 rod 23 wire 30ff electromagnetic induction 20 electrostatic charges 115 electrostatic discharge (ESD) 115 clothing 132 damage 126 footwear 131 equipment grounding connections 47 equipment grounding conductors 60 equipotential bonding 54 equivalent hemisphere 24 exothermic welding 55 explosion limits 112ff extremely low voltage (ELV) 79 fall-of-potential method 11 FELV 79 fence 76 fibrillation 4 flash point 112, 113 flexible metal piping 71ff floors, conducting 131 dissipative 131, 132 flow electrification 120 footing resistance 40 footwear (ESD) 131 force on conductor 153170 Index galvanic series 73 gas pipes 53 ground connection provisions 60 ground grid 93 ground mat resistance 94 ground potential rise (GPR) 93, 97 grounding, at substations 74ff, 93ff grounding conductor 56ff, 60ff grounding systems 45, 79, 80 Helmholz double layer 119 hemispherical electrode 7 hollow square 27 horizontal buried wire 30 ignition 111 level dusts 114, 116 gases 113 liquids 113 ignition sources 114 induced charge 122 inductance, mutual 151, 152 self 150 ionization 134 ionizers 134 isokeraunic map 141 isolation transformer 90 IT-system 89 jumpers 53, 72 keraunic level 141 lightning 137ff current wave 139 IEC protection levels 140 protection system 144 risk factor 142ff lower explosive limit (LEL) 112 Marconite 52 measurement of resistance to ground 11 soil resistivity 18 mesh sizes 146 mesh termination network 146 mesh voltage 98 minimum ignition energy (MIE) 112, 115 moisture, effect on resistivity 17 neutral conductor 80, 87 neutral grounding 74 Onderdonk equation 57 overhead ground wire 40, 157ff oxygen 114 PELV 79 PME 87 power towers, grounding 40 propagating brush discharge 127 protective grounding 79 IT 89 PME 87 TN-C 80 TN-S 84 TT 82 protective earth conductor 81, 84, 87 protective sleeve 59 reinforcement bars 33, 54, 149 relative humidity 133 resistance area 33 resistance of human body 5 resistance ratio 26 resistance to ground 6, 45 resistivity concrete 52 improvement 47 measurement 18ff soil 16ff surface 120, 121 temperature dependence 18 risk assessment 142ff rod configurations circular 27 hollow square 27 multiple 25, 25, 28 single 23 solid square 27 rod length, effect of 24 rods, resistance to ground multiple 28 single 23 three in parallel 26 two in parallel 25 rolling sphere method 153ff SELV 79 separation distance 150, 152 side flashing 150 soil resistivity 16, 17, 47 soil treatment 47ff solid square 27 spark discharge 123 stacks 157 static conductive floors 130, 131 static dissipative floors 130, 131 step voltage 11, 35, 76, 98, 150 Sverak formula 95 striking distance 145, 153 substation grounding 74, 93ff surface charges 115 surface charging 115ffIndex 171 surface resistivity 120, 121 swimming pool 79 tanks 157 thermit welding 55 TN-C 81 TN-S 84 touch voltage 11, 36, 76, 98, 150 tower footing resistance 40 transfer voltage 39 transformer substations 74ff triboelectric series 117 triboelectrification 111 TT-system 82 upper explosive limit (UEL) 112 water pipes 33, 53 welded connections 55 Wenner method 19 work function 117, 120 wrist strap 129, 133 zones of protection 153ff
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