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IS/IEC 62305 SN Earthing Lightning Arrester

LIGHTNING PROTECTION MEASURES As per IEC 62305–1/2010, protection measures may be adopted in order to reduce the risk according to the type of damage. In order to evaluate whether or not lightning protection of a structure is needed, a risk assessment in accordance with the procedures contained in IEC 62305-2 shall be made. The following risks shall be taken into account; R1 – Risk of loss or permanent injury to human life R2 – Risk of loss of services to the public R3 – Risk of loss of cultural heritages R4 – Risk of loss of Economic value (structure, its contents and loss of activity) PROTECTION MEASURES TO REDUCE INJURY OF LIVING BEINGS BY ELECTRIC SHOCK (i) Adequate insulation of exposed conductive parts. (ii) Equipotentialization by means of a meshed earthing system. (iii) Physical restrictions and warning notices. (iv) Lightning equipotential bonding. Note:1 Equipotentialization and an increase of the contact resistance of the ground surface inside and outside the structure may reduce life hazards (See clause-8 of IEC 62305-3/2010) Clause-8: Protection measures against touch voltages/Step voltages. (a) Under normal operation conditions, there are no persons within 3m from the down conductors. (b) A system of at least 10 down conductors is employed. (c) Reduce contact resistance within 3m distance of down conductor by a layer of insulating material. For example, asphalt of 5cm thickness or a layer of gravel 15cm thick. If none of these conditions is fulfilled, provide- (i) Insulation of the exposed down conductor at least using 3mm XLPE. (ii) Equipotentialization by means of a meshed earth termination system. (iii) Warning notices to minimize the probability of access to dangerous area, within 3m of the down conductor. PROTECTION MEASURES TO REDUCE PHYSICAL DAMAGE This is achieved by LPS (Lightning Protection System) which include the following features; (a) Air-Termination System (b) Down conductor system (c) Earth termination system (d) Lightning equipotential bonding (EB) (e) Electrical insulation (and hence separation distance against the external LPS) When LPS is installed, equipotentialization is a very important measure to reduce fire and explosion danger and life hazards. Firefighting appliances kept in the structure may reduce physical damage. PROTECTION MEASURES TO REDUCE FAILURE OF ELECTRICAL AND ELECTRONICS SYSTEM Surge protection measures (SPM) includes; (a) Earthing and bonding measures (b) Magnetic shielding (c) Line routing (d) Isolating Interfaces (e) Coordinated SPD system Protection measures listed above together form the overall lightning protection. The most suitable protection measures are given in IEC 62305-2. LIGHTNING PROTECTION LEVELS Four LPLs are introduced. For each LPL, a set of maximum and minimum lightning current parameters is fixed (LPL I to IV) The maximum values of lightning current parameters are used to design lightning protection components (Eg. Cross section of conductors, thickness of metal sheets, current capability of SPDs and Separation distance against dangerous sparking). The minimum values of lightning current amplitude for the different LPL are used to derive the Rolling Sphere Radius in order to define the Lightning Protection Zone (LPZ0B) which cannot be reached by direct strike

  • 2018-08-28T11:52:03

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