Understanding Lightning and Lightning Protection: A Multimedia Teaching Guide

CHAPTERS and subsections Comment Page

PREFACE xi

INTRODUCTION 1

Guide to use the program 1

1. CLOUD, CYCLONE AND FRONTS 1-0 3

Development of a cloud 1-1 3

Growth of a thunderstorm cloud 1-5 4

Development of a cyclone 1-13 6

Warm and cold fronts 1-21 7

Distribution of thunderstorms 1-25 7

2. ELECTRIC CHARGES IN CLOUDS 2-0 9

Processes of charge separation 2-1 9

Charging process in the liquid phase 2-1 9

Charging process during freezing 2-8 10

Final distribution of charges 2-14 11

Static electric field 2-16 11

Relation to the ionosphere 2-17 12

3. DISCHARGE PROCESSES IN AIR 3-0 13

Photon processes 3-1 13

Excitation by photon 3-2 13

Ionisation and absorption 3-3 14

Recombination 3-4 14

Electron collisions 3-6 14

Excitation by electron 3-9 15

Ionisation by collision 3-10 15

Discharges 3-11 15

Electron avalanche 3-11 15

Streamer discharge 3-18 16

Klydonograph 3-22 17

Leader discharge 3-25 17

4. DEVELOPMENT OF THE LIGHTNING FLASH 4-0 19

Start on drops in the cloud 4-1 19

From leader to main stroke 4-5 20

Multiple stroke 4-13 21

CHAPTERS and subsections Comment Page

Upward leader 4-16 22

The Boys-camera: Principle and construction 4-22 23

The Boys-camera: Operation 4-27 24

Boys-record of ideal lightning 4-30 24

Real Boys-records 4-36 25

5. PHYSICS OF THE LIGHTNING DISCHARGE 5-0 27

Properties of a downward leader 5-1 27

Condition of connecting leader 5-5 28

Striking process 5-11 29

Development of main stroke 5-13 29

Multiple and upward stroke 5-15 30

The current wave 5-19 30

Lightning parameters 5-24 31

Distribution functions 5-28 32

6. CURIOUS LIGHTNING PHENOMENA 6-0 35

Properties of ball lightning 6-1 35

Ball lightning-theories 6-7 37

Resonance theory 6-10 37

Quantum-theory 6-11 38

Theory of magnetic vortex 6-12 38

Photos of ball lightning 6-18 39

Beaded lightning 6-23 40

Stroke from clear sky 6-28 41

Discharge to the ionosphere 6-31 41

7. INDUCED VOLTAGE 7-0 43

Ampère’s law 7-1 43

Rectangular loop + infinite conductor 7-5 44

Rectangular loop + cut conductor 7-8 44

Reduction to basic components 7-10 44

Triangular loop 7-13 45

Polygonal loop 7-16 45

Induced voltage due to direct stroke 7-18 46

Induced current due to direct stroke 7-23 46

Induced voltage due to distant stroke 7-28 47

Induced current due to distant stroke 7-35 48

8. DYNAMIC FORCES DUE TO LIGHTNING 8-0 51

Parallel wires 8-1 51

Force due to lightning on a rod struck at the top 8-8 52

Force due to lightning on a horizontal wire 8-12 53

Force due to lightning on a metal plate 8-15 53

Force of leaded current at inversion of wire 8-18 54

CHAPTERS and subsections Comment Page

Force of leaded current on a tube 8-20 54

Dynamic force on a console 8-22 54

Slit effect 8-27 55

Damage on tree 8-32 56

9. HEAT EFFECTS ON METAL OBJECTS 9-0 59

Heating a metal plate 9-1 59

Change of temperature in a metal plate 9-4 60

Equations of melting a metal plate 9-9 61

Crater and droplets 9-15 62

Melting a wire at contact spot 9-18 62

Melting a wire leading current 9-22 63

Probability of melting 9-30 64

10. LIGHTNING ATTACHMENT 10-0 67

Point of orientation 10-1 67

The striking distance 10-5 68

Distribution and density functions 10-7 68

The expected frequency of stroke 10-10 69

The principle of calculation 10-10 69

Collection space 10-17 70

11. COLLECTION SPACES OF STRUCTURES 11-0 73

The principle of collection space 11-1 73

Dividing the collection space 11-3 74

Two conductors 11-6 74

Lightning rod on tower 11-9 75

Air terminations of block-house 11-13 75

The collection space of one mesh 11-25 77

12. PROTECTIVE EFFECT ON FLAT ROOF 12-0 79

Air termination systems on blockhouse 12-1 79

Diagrams related to several air terminations 12-4 80

Application of rolling sphere method 12-8 81

13. PROTECTION OF INCLINED ROOF 13-0 83

Types of air termination systems 13-1 83

Attraction of roof and eaves 13-6 84

Effect of electrodes on eaves 13-11 85

Effect of electrodes on the edges 13-15 85

Attraction of unprotected edges 13-23 87

Stroke-free period 13-26 87

14. RESIDUAL RISK OF LIGHTNING PROTECTION 14-0 89

The flow diagram 14-1 89

Equivalent area of a structure 14-2 89

Cases of the point of strike 14-11 91

Cases of damaging stroke 14-18 92

Intercepted stroke 14-19 92

CHAPTERS and subsections Comment Page

Striking the roof 14-23 93

Calculation of risk 14-27 94

Weighting the consequences 14-28 95

Resulting damage 14-38 97

Resulting frequency of weighted damage 14-40 97

Resulting risk 14-44 98

15. CLASSIFICATION OF STRUCTURES 15-0 101

Classes of structures 15-1 101

Height and surroundings 15-12 103

High surroundings 15-13 103

Increased danger of stroke 15-18 104

Classes according to height 15-26 106

Effect of the soil profile 15-27 106

The materials of roof 15-31 107

Further classifications 15-37 108

16. AIR TERMINATION SYSTEMS 16-0 111

Level of risk and protection 16-1 111

Construction methods 16-3 111

Protective angle 16-3 111

Rolling sphere 16-7 112

Mesh size 16-9 112

Degrees of Hungarian standard 16-12 113

Natural air termination 16-13 113

Simplified air termination 16-17 114

Data of higher degrees 16-19 114

Distance to the structure 16-21 115

Forms of air terminations 16-28 116

17. DOWN CONDUCTORS AND METAL OBJECTS 17-0 119

Down conductors 17-1 119

Calculation of current paths 17-1 119

Example of current path 17-9 120

Positioning along the perimeter 17-15 121

Degrees of down conductors 17-17 121

Forms of down conductors 17-22 122

Vertical metal structures 17-26 123

Dangerous loops 17-26 123

Bonding metal structures 17-30 124

Insulating spacers 17-34 124

Elevators 17-37 125

18. EARTHING OF LIGHTNING PROTECTION SYSTEM 18-0 127

Degrees of earthing 18-1 127

Natural earthing 18-2 127

Simple earthing systems 18-5 128

CHAPTERS and subsections Comment Page

Earthing resistance 18-10 129

Normal and enhanced systems 18-17 130

Earthing by foundation 18-22 131

Soil resistivity 18-27 132

Measurement of earthing resistance 18-30 132

Impulse earthing 18-32 132

19. LIGHTNING ELECTROMAGNETIC IMPULSE 19-0 135

Conductive coupling 19-1 135

Inductive coupling 19-3 136

Capacitive coupling 19-5 136

Distribution of current 19-7 136

Arriving current along a single line 19-10 137

Arriving current along branching line 19-15 138

Faraday holes 19-20 139

Shielded entrance 19-25 139

Shielded cable 19-30 140

Circuit of lightning 19-32 141

20. GRADED SURGE-PROTECTION 20-0 143

Operation principles 20-1 143

Three stage with resistors 20-6 144

Influence of distance between stages 20-11 145

Propagation of waves 20-19 146

Waves on devices 20-27 147

21. SURGE PROTECTION DEVICES 21-0 149

Gas filled arrester 21-1 149

Arc blowing spark gap 21-5 150

Gliding spark gap 21-9 150

Encapsulated arrester 21-13 151

Characteristics of gaps 21-18 152

The varistor 21-20 152

Characteristics of varistor 21-29 153

Types of protection devices 21-33 154

22. INTERNAL LIGHTNING PROTECTION ZONES 22-0 157

Structure of zones 22-1 157

Standardised lightning parameters 22-5 158

Networks of information systems 22-6 158

Tray configuration 22-17 160

23. CONNECTION TO ELECTRIC POWER NETWORK 23-0 161

Striking the supply line 23-1 161

Striking the air termination 23-10 162

TT system 23-17 163

Outdoor kWh box 23-22 164

CHAPTERS and subsections Comment Page

24. PROTECTION OF ELECTRONIC DEVICES 24-0 167

Protection of personal computer 24-1 167

Protection of television 24-10 169

Relay station 24-16 170

25. LIGHTNING MEASUREMENT AND LOCALIZATION 25-0 171

Measuring of lightning current 25-1 171

Magnetic card 25-2 171

Magnetic link 25-5 172

Shunt resistor 25-9 172

Coil of Rogowski 25-13 173

Reflection of the current wave 25-18 174

Localising by direction finding 25-21 174

Localising by pulse arrival time 25-24 175

Lightning detection systems 25-28 175

26. THE MANKIND IN THE THUNDERSTORM 26-0 177

Danger in open air 26-1 177

Danger on or beside a tree 26-5 178

Step voltage 26-11 179

What to do outdoors? 26-14 179

Danger on a bicycle 26-18 180

Danger at a car 26-22 180

Danger at a truck 26-26 181

Danger in water 26-30 182

Danger in boats and vessels 26-34 182

REFERENCES 185

INDEX 189