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DIN Standards Committee Building and Civil Engineering

Overview

Standard series DIN EN 62305 presents an overall concept regarding lightning protection (lightning protection system) for structures, taking fully into account: - the hazard by direct and indirect flashes by electricity and the magnetic field of the lightning, - the types of damage due to step and touch voltages, dangerous sparking, fire, explosion, mechanical and chemical actions and overvoltages, - the objects to be protected (buildings, persons, electrical and electronic equipment), and - the protection measures which include air-termination systems, down conductors, earth-termination systems, equipotential bonding measures, surge protective devices, spatial shielding and cable routing and shielding belong to. Lightning flashes to earth are hazardous to structures and to lines that lead into such structures. They can result in damage to the structure and to its contents, failure of associated electrical and electronic systems or injury to living beings in or close to the structure. Consequential effects of such damage and system failures may also affect the surroundings of the structure or may involve its environment. To reduce the hazard of potential damage due to lightning, protection measures may be required. Whether they are needed, and to what extent, should be determined by risk assessment in accordance with this standard. The risk, defined as the probable average annual loss in a structure due to lightning flashes, depends on the annual number of lightning flashes influencing the structure, the probability of damage by one of the influencing lightning flashes and the mean amount of consequential loss. Lightning flashes influencing the structure may be divided into - flashes terminating on the structure; - flashes terminating near the structure, direct to connected lines (power, telecommunication lines,) or near the lines. Flashes to the structure or a connected line may cause physical damage and life hazards. Flashes near the structure or line as well as flashes to the structure or line may cause failure of electrical and electronic systems due to overvoltages resulting from resistive and inductive coupling of these systems with the lightning current. Moreover, failures caused by lightning overvoltages in users' installations and in power supply lines may also generate switching type overvoltages in the installations. DIN EN 62305-2 (VDE 0185-305-2) uses a risk assessment to at first determine the necessity for protection of lightning for structures and then to select the optimal technical and most efficient protection measures which are described in detail in the actual protection standards (installation standards Part 3 and Part 4). The remaining risk is then determined. The object to be protected is subdivided into one or more lightning protection zone(s) (LPZ). The geometric limits, the relevant characteristics, the threat levels for lightning and the types of damage to be considered are specified for each lightning protection zone. Based on the unprotected condition of the object, the residual risk is reduced by means of applying (further) protection measures until it is below the tolerable risk. Economic evaluation of protection measures for the type of damage "economic loss" takes place on the basis of its cost and the possible economic damage in and near a structure due to the effects of lightning. This standard considers protection measures for structures including living beings within them and electrical and electronic systems. The methods described can be used for simple determination of the protection class of a lightning protection system in accordance with DIN EN 62305-3 (VDE 0185-305-3) as well as for specification of complex protection measures (Surge Protection Measures, SPM) against lightning electromagnetic impulses based on DIN EN 62305-4 (VDE 0185-305-4). The annexes describe methods for the assessment of the annual number of dangerous events due to lightning, the assessment of probability of damage to structures and losses. Cost-benefit analyses for economic loss are represented and case studies for structures are carried out. The new edition of DIN EN 62305-2 (VDE 0185-305-2) includes the following changes with respect to the previous edition: - risk assessment for lines (in particular telecommunication lines) is excluded from the scope. Lines leading into a structure are considered exclusively as a source of damage. - Injuries of living beings caused by electric shock inside the structure are considered. - Tolerable risk of loss of cultural heritage has been lowered. - Extended damage to surroundings structures or to the environment is better accounted for. - The collection areas for flashes to and nearby a structure as well as collection areas relevant to flashes to and nearby a line have been revised and new findings have been incorporated. - The annex on the assessment of probability has been revised; some equations for calculation of these probabilities have been changed. - A more precise distinction between surge protective devices for the purpose of lightning protection equipotential bonding and the use of coordinated systems of surge protective devices is made. Better consideration of the various protection effects of these measures for direct and indirect effects of lightning is thus possible. - Impulse withstand voltage level of equipment was extended down to 1 kV. - The reduction factors as well as the damage factors have been updated. In addition, the specification of fundamental equations for calculation of the damage factors is no longer included. Basically only the "typical values" are shown in a table format. In the event of a risk assessment for structures with risk of explosion, consideration of zones 1 and 2 as well as 21 and 22 is now possible in addition to zones 0 and 20. This is done by means of a graduated specification of the parameter for structures with risk of fire or explosion. - For assessment of the amount of loss, tables are provided for calculation of the economic loss in order to select the relative amount of loss in all cases (provided that no other more precise data is available to the planner). - The examples of applications have been revised and updated. - The Simplified IEC Risk Assessment Calculator (SIRAC) has been removed. The responsible committee is K 251 "Blitzschutzanlagen und Blitzschutzbauteile" ("Lightning protection systems and lightning protection components") of the DKE (German Commission for Electrical, Electronic and Information Technologies) at DIN and VDE.

Document: references other documents

Document: referenced in other documents

Responsible national committee

DKE/K 251 - Blitzschutzsysteme und Blitzschutzbauteile