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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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