The Protection of Telecommunication Lines and Equipment against Lightning Discharges
CHAPTER 1 – INTRODUCTION
1. General
2. Aims and limits of protection against lightning
3. Definitions
3.1 Thunderstorm day
3.2 Isokeraunic line
3.3 Impulse current
3.4 Impulse and surge voltages
3.5 Protective devices against surges
3.6 Earthing network
3.7 Diffusion impedance of an earthing network
3.8 Transfer (or coupling) impedance of a metal cable sheath
3.9 Quality factor of a metal-sheathed cable (resistivity factor for lightning voltages)
3.10 Screening factor 1 of a metal cable sheath
CHAPTER 2 – ATMOSPHERIC DISCHARGES AND RESULTANT PHYSICAL PHENOMENA
1. Electrical charge distribution and resultant physical phenomena
2. Characteristics of discharge phenomena
3. Frequency of lightning strokes
4. Impulse breakdown of dielectrics
APPENDIX (to Chapter 2) – Waveform of impulses simulating lightning discharge currents
1. Theoretical simulated impulse
2. Practical simulated impulse
3. Equivalent diagram of the lightning current circuit
CHAPTER 3 – THE ATMOSPHERIC ELECTRIC FIELDS ASSOCIATED WITH THUNDERSTORMS AND LIGHTNING DISCHARGES AND THEIR EFFECTS
1. General
1.1 Factors affecting the voltage in an overhead line conductor
2. Electric field strength in the atmosphere
2.1 Field when there is no lightning 1
2.2 Field when lightning occurs
3. Voltages in a horizontal, overhead conductor
3.1 Lightning discharges to earth within about 3 km of a conductor and assuming a perfectly conducting earth
3.2 Lightning discharges to earth within about 3 km of a conductor, when the earth resistance is not zero
3.3 Lightning discharges more than 3 km away from a conductor and cloud discharges
4. Effects produced in the ground by lightning strokes
5. Other effects caused by lightning discharges
5.1 Effects on metal conductors
5.2 Effects on non-conducting material
APPENDIX (to Chapter 3) – Critical distance from the point of impact for cables with an insulating covering
CHAPTER 4 – THE EFFECTS OF LIGHTNING DISCHARGES TO OVERHEAD AND UNDERGROUND TELECOMMUNICATION LINES
1. Lightning strokes which terminate on an overhead route
1.1 The propagation and reflection of lightning surges and the effects on a multi-pair overhead route
1.2 The effects on aerial cables
2. Lightning strokes which terminate in the vicinity of a buried telecommunication cable
2.1 Effects on cables with metal sheaths
2.2 Effects on cables with an insulating covering over the metal sheath
2.3 Effects on cables with non-metallic sheaths
2.4 Effects on cables connected to overhead lines
2.5 Effects on cables to mountain top radio stations
2.6 Effects on cable conductors and associated insulation
APPENDIX 1 (to Chapter 4) – Propagation of lightning currents on an overhead line
APPENDIX 2 (to Chapter 4) – Simplified formula for the impulse voltage between conductors and metal sheath at the point of entry of the lightning current
CHAPTER 5 – PROTECTIVE DEVICES
1. General
2. Types of lightning protectors
2.1 Air gap protectors
2.2 Gas-filled protectors
3. Junction diodes
4. Fuses
5. Coupling coils
6. Choke coils in series
7. Transverse protectors
8. Forward protectors
9. Shields or guards
9.1 Shield wires placed above an open-wire line
9.2 Shield-wires above buried cables
10. Iron pipes (for underground cables)
11. Cables of special design
11.1 Transfer impedance of the metallic sheath
11.2 Insulation of the conductors
11.3 Quality factor
11.4 Equipments connected to cables of special design
12. Code, construction and protection of plastic-sheathed or plastic-covered cables
13. Specification for transformers with high dielectric strength used in conjunction with cables of special design
APPENDIX (to Chapter 5) – Calculation of cable characteristics with increased resistance to lightning currents and with layer sheaths
1. General
2. Calculation (see Figure 5.3)
3. Composition of the cable
4. Example of calculation
5. Cable behaviour in practice
6. Use of cables with layer sheath in case of induced voltages