These parts of the standard are introduced here. In these parts underwent periodic technical review, with updated parts 1, 3 and 4 released in Updated part 2 is currently under discussion and is expected to be published in late It differs from BS in as much that this new part has four Classes or protection levels of LPS, as opposed to the basic two ordinary and high-risk levels in BS It classifies the sources and types of damage to be evaluated and introduces the risks or types of loss to be anticipated as a result of the lightning activity. Furthermore, It defines the relationships between damage and loss that form the basis for the risk assessment calculations in part 2 of the standard.
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These parts of the standard are introduced here. In these parts underwent periodic technical review, with updated parts 1, 3 and 4 released in Updated part 2 is currently under discussion and is expected to be published in late It differs from BS in as much that this new part has four Classes or protection levels of LPS, as opposed to the basic two ordinary and high-risk levels in BS It classifies the sources and types of damage to be evaluated and introduces the risks or types of loss to be anticipated as a result of the lightning activity.
Furthermore, It defines the relationships between damage and loss that form the basis for the risk assessment calculations in part 2 of the standard.
Lightning current parameters are defined. These are used as the basis for the selection and implementation of the appropriate protection measures detailed in parts 3 and 4 of the standard. Part 1 of the standard also introduces new concepts for consideration when preparing a lightning protection scheme, such as Lightning Protection Zones LPZs and separation distance. Figure 12 on page depicts the types of damage and loss resulting from lightning.
Please see page for more details about this guide. Scheme design criteria The ideal lightning protection for a structure and its connected services would be to enclose the structure within an earthed and perfectly conducting metallic shield box , and in addition provide adequate bonding of any connected services at the entry point into the shield.
This, in essence, would prevent the penetration of the lightning current and the induced electromagnetic field into the structure. However, in practice, it is not possible or indeed cost effective to go to such lengths. This standard thus sets out a defined set of lightning current parameters where protection measures, adopted in accordance with its recommendations, will reduce any damage and consequential loss as a result of a lightning strike. This reduction in damage and consequential loss is valid provided the lightning strike parameters fall within defined limits, established as Lightning Protection Levels LPL.
Lightning Protection Levels LPL Four protection levels have been determined based on parameters obtained from previously published technical papers. Each level has a fixed set of maximum and minimum lightning current parameters. These parameters are shown in Table 6. The maximum values have been used in the design of products such as lightning protection components and Surge Protective Devices SPDs. The minimum values of lightning current have been used to derive the rolling sphere radius for each level.
The general principle is that the equipment requiring protection should be located in an LPZ whose electromagnetic characteristics are compatible with the equipment stress withstand or immunity capability. The assessment and management of risk are now significantly more in-depth and extensive than the approach of BS The ultimate aim of the risk assessment is to quantify and if necessary reduce the relevant primary risks i.
Each primary risk Rn is determined through a long series of calculations as defined within the standard. If the actual risk Rn is less than or equal to the tolerable risk RT , then no protection measures are needed. If the actual risk Rn is greater than its corresponding tolerable risk RT , then protection measures must be instigated. The above process is repeated using new values that relate to the chosen protection measures until Rn is less than or equal to its corresponding RT.
The main body of this part of the standard gives guidance on the design of an external Lightning Protection System LPS , internal LPS and maintenance and inspection programmes. External LPS design considerations The lightning protection designer must initially consider the thermal and explosive effects caused at the point of a lightning strike and the consequences to the structure under consideration.
Depending upon the consequences the designer may choose either of the following types of external LPS: — Isolated — Non-isolated An Isolated LPS is typically chosen when the structure is constructed of combustible materials or presents a risk of explosion. Conversely, a non-isolated system may be fitted where no such danger exists.
This will ensure that in the event of a lightning current discharge to the structure, the correct design and choice of components will minimize any potential damage. Air termination system The role of an air termination system is to capture the lightning discharge current and dissipate it harmlessly to earth via the down conductor and earth termination system.
Therefore it is vitally important to use a correctly designed air termination system. It highlights that the air termination components should be installed on corners, exposed points and edges of the structure.
The three basic methods recommended for determining the position of the air termination systems are: — The rolling sphere method.
BS EN 62305-4:2011 Protection against lightning
BS EN 62305-4:2011
BS EN 62305-4:2006