Furse Earthing & lightning protection

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Vydal: ABB s.r.o.

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An external LPS consists of: • Air termination system • Down conductor system • Earth termination system These individual elements LPS should be connected together using appropriate lightning protection components (LPC) complying (in the case 62305) with IEC/BS 62561 series. These LPLs equate directly classes Lightning Protection System (LPS). highlights that the air termination components should installed corners, exposed points and edges the structure.— Technical reference IEC/BS 62305-3 Physical damage to structures life hazard IEC/BS 62305-3. The main body this part the standard gives guidance the design external Lightning Protection System (LPS), internal LPS and maintenance and inspection programmes. Air termination system The role air termination system capture the lightning discharge current and dissipate it harmlessly earth via the down conductor and earth termination system. IEC/BS 62305-3 advocates the following, any combination, for the design the air termination: • Air rods (or finials) whether they are free-standing masts linked with conductors form mesh on the roof • Catenary (or suspended) conductors, whether they are supported free-standing masts or linked with conductors form mesh the roof • Meshed conductor network that may lie direct contact with the roof suspended above it (in the event that paramount importance that the roof not exposed a direct lightning discharge) The standard makes quite clear that all types of air termination systems that are used shall meet the positioning requirements laid down the body of the standard. This will ensure that the event a lightning current discharge the structure, the correct design and choice components will minimise any potential damage. This part the suite standards deals with protection measures and around structure. LPL Class LPS I I II II III III IV IV — Table Relation between Lightning Protection Level (LPL) and Class LPS (IEC/BS 62305-3 Table 1) 109 TECHNIC REFERENCE IEC/BS 62305 PHYSIC DAMAGE STRUCTURES LIFE HAZARD . Conversely non-isolated system may fitted where such danger exists. Lightning Protection System (LPS) IEC/BS 62305-1 has defined four Lightning Protection Levels (LPLs) based probable minimum and maximum lightning currents. External LPS design considerations The lightning protection designer must initially consider the thermal and explosive effects caused at the point lightning strike and the consequences to the structure under consideration. Depending upon the consequences the designer may choose either the following types external LPS: • Isolated • Non-isolated External LPS design considerations An Isolated LPS typically chosen when the structure is constructed combustible materials presents a risk explosion. The three basic methods recommended for determining the position the air termination systems are: • The rolling sphere method • The protective angle method • The mesh method These methods are detailed over the following pages. Therefore important to use correctly designed air termination system. The correlation between the four levels LPL and LPS identified Table essence, the greater the LPL, the higher class LPS required