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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For example clause 4. An installed SPD has its protection level increased by the voltage drop on its connecting leads.
Lightning Protection Standard BS EN 62305
Clearly this arrangement is only suitable for smaller structures or isolated pieces of equipment. It comprises conductors that are installed in the concrete foundation of the structure. BS EN categorises visual inspection, complete inspection and critical systems complete inspection dependent on the appropriate LPL. If the result shows R RT then the structure is adequately protected for a particular type of loss.
Poor coordination could mean that an overvoltage SPD is subjected to an excess of surge energy placing both itself and connected equipment at risk from damage. BS EN part 1 is an introduction to curse 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.
Loss of 62035 life or permanent injuries Loss of service to the public Loss of cultural heritage Table 3. Lasting from microseconds to milliseconds large transient overvoltages can be caused by the secondary effects of lightning transients can also be caused by electrical switching of large inductive loads such as air-conditioning units and lifts.
Vertical air termination Concealed conductor Non-conventional air termination systems A lot of technical and commercial debate has raged over the years regarding the validity of the claims made by the proponents of such systems.
However, in practice it is not possible nor indeed cost effective to go to such measures. If the cables power, telecom etc entering the structure are of a shielded construction, then these shields should be connected directly to the equipotential bonding bar.
This will ensure that critical equipment housed within the structure has a much greater degree of protection and thus continued operation.
In addition to this, connecting leads should be tightly bound together over as much of their length as possible, using cable ties or spiral wrap.
Protection level Visual inspection years Complete inspection years Critical systems complete inspection years 1 1 Critical systems — typically, LPS exposed to mechanical stresses created by high winds and other such extreme environmental conditions — should have a complete inspection annually.
Like all security measures, they should wherever possible be viewed as cumulative and not as a list of alternatives.
The general idea is to identify or create zones within the structure where there is less exposure to some or all of the effects of lightning and to coordinate these with the immunity characteristics of the electrical or electronic equipment installed within the zone. All metal vs, power and data cables should, where possible, enter or leave the structure at the same point, so that it or its armouring can be bonded, directly or via equipotential bonding SPDs, to the main ugide terminal at this single point.
The full electromagnetic field occurs here.
A Guide to BS EN Protection Against Lightning_图文_百度文库
Square clamp Part no CS www. On a hot day, warm air rises from warm ground and is replaced by cooler air drifting down. This can be expressed thus The number of dangerous events can now be determined for each specific risk component, ie ND NDa is the average annual number of dangerous events for the structure. Harmonics ‘Sags’ or ‘dips’ are decreases in the supply voltage, lasting no more than a few seconds.
Bonding can also be accomplished by the use of surge protection devices SPDs where the direct connection with bonding conductors is not suitable. A typical test arrangement is illustrated in Figure 4. Charge separation Advancing cold air mass can wedge warm air upward to start an updraft at the cold front New cloud How many clouds form is well understood.
Test resports are available for all the connection components tested. The protective angle afforded by an air rod is clearly a three dimensional concept. Application of the protection angle method to elevated meshed conductors forming a non-isolated system Figure 4. Annex NC helps to assess the amount of loss to a structure LX. A line is then struck from the point where the sphere touches the air rod A down to the reference plane Dfinishing at point C.
This could be due, following a lightning discharge, to lightning current flowing in the external LPS or indeed other conductive parts of the structure and attempting to flash or spark over guidr internal metallic installations. BS EN part 5which relates to this latter type of damage, will ultimately be deleted from the standard.
How many metallic services are there entering or leaving the structure? This can be achieved by placing lightning conductors, sufficiently far away from any conductive parts that has routes leading into the structure. Protection measures for roof mounted equipment containing electrical equipment This is an issue that has already caused some debate. Lightning equipotential bonding for internal systems If the conductors within the structure have an outer screening or are installed within metal conduits then it may be sufficient to only bond these screens and conduits.
Furse release 3rd edition of their renowned Guide to Lightning Protection
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.
The inspection should include the checking of all relevant technical documentation and a comprehensive visual inspection of all parts of the LPS along with the LPMS measures. Reapplying the rolling sphere can show the effectiveness of the design produced. Super structures approaching almost 1km in height are now being constructed. To make it easier to cross reference the document, a specific clause reviewed in Annex E corresponds to the same numbered clause in the main text.