![]() ![]() ![]() Before and during the appearance of the lightning stroke, discharges can be seen both within the cloud and between clouds. The atmospheric electrical field on the ground, about 600 V/m in fine weather is reversed and can reach an absolute value of 15 to 20 kV/m when a ground discharge is imminent (the lightning stroke). Thus the cumulo-nimbus formation constitutes a sort of huge plate /ground capacitor whose median distance can often reach 1 to 2 km. positive over the part of the ground nearby). Conse- quently, the lower part of the cloud causes the development of electrically opposite charges (i.e. In a typical storm cloud, the upper part, consisting of ice crystals, is normally positively charged, whilst the lower part, consisting of water droplets, is negatively charged. The existence of extreme temperature gradients in a cumulo-nim- bus (the temperature can drop to -65 ☌ at the top) generates very rapid ascending air currents, and results in the electrical energisation of the water particles. Its highly character- istic shape is often compared with the profile of an anvil of which it displays the upper and lower horizontal planes. This type of cloud is very extensive, both horizontally (about 10 km in diameter) and vertically (up to 15 km). 2 | ABB hélita® lightning protection systems Lightning mechanism and location Storms The presence of unstable, moist and warm air masses gives rise to the formation of cumulo-nimbus storm clouds. ABB hélita® lightning protection systems | 1 Lightning mechanism and location 2 Lightning protection technologies 3 Lightning protection risk analysis 8 Lightning protection technical study 9 Procedure for measuring the Early Streamer Emission of an ESE air terminal according to standard NF C 17-102 appendix C 10 Tests and research 12 Lightning capture devices 14 Down conductors 16 Equipotential bonding 19 Earth termination systems 21 Inspection ESEAT maintenance 23 Lightning air terminal range ESEAT typical installation 24 Early Streamer Emission 26 Early Streamer Emission Air Terminal - ESEAT 27 Single Rod Air Terminal - SRAT 29 Extension masts 30 Extension masts - Industrial chimney offset and bracket 31 Roof fixing accessories 32 Pylons 33 Lateral fixations 34 Conductors and coupling accessories 35 Conductor fasteners 36 Earth coupling accessories 38 Earthing system 39 Equipotential bonding 41 Meshed conductors Typical installation 42 Accessories 43 Index 44 hélita® lightning protection systems External lightning protection 3. hélita® lightning protection systems External lightning protection Main catalog 2. ![]()
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