Furse have now launched an updated Guide to BS EN Protection Against Lightning. This latest edition incorporates guidance on the. This handbook offers a guide for any designers of the structural Lightning protection system to comply with the requirements of BS EN range of standards. An overview of BS EN , its impact on lightning protection and the support and advice Earthing design considerations and full details of the Furse range of earthing materials .. illustrations and design examples, the Guide provides.
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A Guide to BS EN Protection Against Lightning_图文_百度文库
As such, evaluating R4 Risk of loss of economic value determines whether the economic benefits of providing lightning protection is cost effective against the physical loss of equipment, not the losses or downtime which are also due to the malfunction of equipment. Annex A provides information on how to assess the annual number of dangerous yo NX.
Harmonics ‘Sags’ or ‘dips’ are decreases in the supply voltage, lasting no more than a few seconds. Furss most practical cases, where a shield exists on a service cable, it is difficult to determine whether the shield material 623305 dimensions is capable of handling the potential surge current. General Principals BS EN part 1 is an introduction to the other parts of the standard and essentially describes how to design a Lighting Protection System LPS in accordance with the accompanying parts of the standard.
Furse release 3rd edition of their renowned Guide to
This is to ensure that those reinforcing bars likely to carry lightning currents have secure connections from one length to the next. Prior to this was BS CP, first published in One of the gudie changes to realise is that this new approach to risk management looks at risk in a far broader sense than merely the physical damage that can be caused to a structure by a lightning discharge.
However the correct meaning of loss of service to the public lies in the loss that can occur when a service provider whether that be a hospital, financial institution, manufacturer etc cannot provide its service to its customers, due to lightning inflicted damage.
In essence, structural lightning protection can no longer be considered in isolation, protection against transient overvoltages or electrical surges are integral to the new standards. Thunderstorm days per year Td Flashes per km2 per year Ng 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 0.
Furse release 3rd edition of their renowned Guide to Lightning Protection
Similarly the collection area of flashes striking near a line is determined by: Bonding can also be accomplished by the use of surge protection devices SPDs where the direct connection with bonding conductors is not suitable.
The pure logistics of compiling so much information and gaining consensus over many technical points has not been easy. So we can state that: R1 risk of loss of human life R2 risk of loss of service to the public R3 risk of loss of cultural heritage R4 risk of loss of economic value Hereafter the primary risks will be referred to collectively as Rn where the subscript n indicates 1, 2, 3 or 4 as described above.
Creating an equipotential plane by means of a meshed conductor earthing arrangement would be effective in reducing the step voltage threat. If the rods are arranged in a square it is the distance between two diagonally opposite rods see Figure 4. The SPDs ability to survive and achieve a suitable protection level when installed clearly depends upon the size of the overvoltage it will be subject to.
The collection area is based on a ratio of 1: Reapplying the rolling sphere can show the effectiveness of the design produced. We have, where it has been possible, corrected the errors in this guide. Insulating plate Conductor fixing Conductor Connection component Electrical connections 20mm 20mm mm Figure 4. Cantilevered structure To reduce the risk of the person becoming an alternative path for the lightning current to that of the external down conductors, then the following condition should be satisfied: Lightning equipotential bonding for external conductive parts should be carried out as near to the point of entry into the structure as possible.
LEMP protection measures also have to operate and withstand the environment in which they are located considering factors such as temperature, humidity, vibration, voltage and current. This includes many countries in regions such as the Far East who have adopted BS over the years and have significantly higher lightning activity than most other countries throughout the world.
The voltage protection levels or let-through voltages of installed SPDs must be coordinated with the insulation withstand voltage of equipment to prevent permanent damage.
Additionally, the reinforcing bars — both horizontal fuese vertical — in many new structures will be so numerous that they serve as an electromagnetic shield which goes some way in protecting the electrical and electronic equipment from interference caused by lightning electromagnetic fields.
The greater the number of down conductors, the lesser the current that flows down each. Air rods or free standing masts The effectiveness of an isolated free standing mast used to protect a small object can be proven by the protection angle method.
An external LPS consists of: Thus the protective angle method is only valid up to the height of the appropriate rolling sphere radius. BS EN categorises visual inspection, complete inspection and critical systems complete inspection dependent on the appropriate LPL.
BS EN series now treats the aspect of internal protection lightning current and overvoltage protection as an important and integral part of the standard and devotes part 4 to this issue. Sometimes it is not possible to install down conductors down a particular side of a building due to practical or architectural constraints.
Lightning Protection Standard BS EN 62305
gurse The line must bisect the sphere circle such that the areas shaded of over and under estimation of protection when compared to the rolling sphere method are equal. Here equipment is protected against lightning, both direct and indirect strikes to the structure and services, with an LPMS. Many theories have been put forward but everyone seems to agree that in a thunder-cloud, ice crystals become positively charged while water droplets carry a negative charge.
Protection measures for roof mounted equipment containing electrical equipment This is an issue that has already caused some debate. Risk Management BS EN part 2 risk management approach, does not concentrate so much on the purely physical damage to a structure caused by a lightning discharge, but more on the risk of loss of human life, loss of service to the public, loss of cultural heritage and economic loss.
Example of mesh air termination 37 www. Application of the protection angle to bss isolated free standing mast Once again if the system does not need to be isolated from the structure then air rods fitted to the roof of the structure could be employed. This can be achieved with the use of a meshed earthing system.
This is in essence, the earthing system used in BS where each down conductor has an earth electrode rod connected to it. Additionally, it is good practice to provide warning notices and fyrse restrictions where possible.