Translate PDF. These parts to 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 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 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.
The relationships of all of the above parameters are This in essence would prevent the penetration of the summarised in Table 5. However, in practice it is not possible or indeed cost For a more detailed explanation of the general effective to go to such lengths. This reduction in damage and IEC equivalent. Please see page for more details consequential loss is valid provided the lightning strike about this guide.
Each level has a fixed Minimum 3 5 10 16 set of maximum and minimum lightning current current kA parameters. The assessment and management of risk is 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 NO series of calculations as defined within the standard. 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.
StrikeRisk risk management software An invaluable tool for those involved in undertaking the complex risk assessment calculations required by BS EN , StrikeRisk facilitates the assessment of risk of loss due to lightning strikes and transient overvoltages caused by lightning.
Contact Furse for more details about StrikeRisk. These LPLs equate potential damage. Therefore it is vitally important to use a I I correctly designed air termination system. Depending upon positioning requirements laid down in the body of the the consequences the designer may choose either of standard. It highlights that the air termination the following types of external LPS: components should be installed on corners, exposed l Isolated points and edges of the structure. The basic concept of applying the rolling angle sphere to a structure is illustrated in Figure Furthermore the new standard uses the height of the air termination system above the reference plane, whether that be ground or roof level The rolling sphere method was used in BS , the See Figure The protective angle method is suitable for simple shaped buildings.
However this method is only valid up to a height equal to the rolling sphere radius of the The protective angle method appropriate LPL. The protective angle method is a mathematical simplification of the rolling sphere method. The protective angle a is the angle created between the 1 tip A of the vertical rod and a line projected down to h1 2 the surface on which the rod sits see Figure The protective angle differs with varying height of the air rod and class of LPS.
The outcome was to remain with the information housed within this standard. Natural components So on all structures particularly with flat roofs, When metallic roofs are being considered as a natural perimeter conductors should be installed as close to air termination arrangement, then BS gave the outer edges of the roof as is practicable. Vertical air puncture, hot spot or ignition problems. The air rods should be spaced not more than 10 m apart and if strike plates are used as an alternative, these should be strategically placed over the roof area not more than 5 m apart.
The greater the number of down conductors the better the lightning current is shared between them. This is enhanced further by equipotential bonding to the conductive parts of the structure. Lateral connections sometimes referred to as coronal bands or ring conductors provided either by fortuitous metalwork or external conductors at regular intervals are also encouraged.
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.. This in turn could have a guice bearing on the specific types of loss as defined in the next section.
These have been transferred to BS ENand also illustrated in this guide. The two meet and form a complete conducting path along which a massive current attempts to flow in order to equalise the difference in potential between cloud and ground. If these internal conductors are neither screened or located in metal conduits, they should be bonded using suitably designed Rn. This will ensure that critical equipment housed within the structure has a much greater degree of protection and thus continued operation.
It is for this reason that lightning can strike the side of tall structures rather than at their highest point. Air terminal base Part no SD 60 Figure 4. This type of event occurs with tall or exposed structures.
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. Photographs shown in Figures 4.
If the electrical services are effectively screened but are not supplying electronic equipment, then no additional measures are required. Down conductors fn wherever possible be installed at each exposed corner of the structure as research has shown these to carry the major part of the lightning current.
Following a risk evaluation in accordance with BS ENthe choice of suitable equipotential bonding SPDs is determined by a number of factors, which can be presented as follows: Like all security measures, they should wherever possible be viewed as cumulative and not as a list of alternatives.
Transient overvoltage Transient overvoltages caused by lightning can reach magnitudes of 6, volts in a well-insulated power distribution bz. Also included are tensile, adhesion, bend and environmental test criteria. Simple determination of the protective angle www. New standards on lightning protection BS For such high partial lightning currents to flow, the conductor size of the power or telecom line would have to be substantial, as indeed would ancillary devices such as in-line over-current fuses.
Requirements for conductors and earth electrodes BS EN For example the lightning current SPD at the service entrance should sufficiently handle the majority of surge energy, thus leaving the downstream overvoltage SPDs to control the overvoltage. This is in order to provide an effective zone of protection using the protective angle method.
These values therefore represent the most common lightning scenario in practice. Here equipment is protected against lightning, both direct and indirect strikes to the structure and services, with an LPMS. BS EN describes a number of measures to minimise the severity of transient overvoltages caused by lightning. YES NO Establish a zone of protection ZOP for the equipment using an air rod, suspended conductor or other means Establish a zone of protection ZOP for the equipment using an air rod, suspended conductor other means while ensuring separation distance s Con?
An installed SPD has its protection level increased by the voltage drop on its connecting leads. Additionally, Tables 2 and 4 from BS EN give information relating to the mechanical and electrical requirements of the conductors and earth electrodes. The designer must ascertain various weighting factors relative to the structure from his client along with various assigned values from the appropriate tables in Annexes A, NB fo NC of BS EN Relationship between thunderstorm days per year and lightning flashes per square kilometre per year 27 www.
This is due to the increasing importance given to the protection against LEMP Lightning Electromagnetic Impulsewhich can cause immeasurable and irreparable damage as well as disastrous consequential effects to the electrical and electronic systems housed within a structure.
However, adoption of the aforementioned precautions is good practice. Loop areas To minimise loop areas, mains power supply cables and yuide communication, signal, or telephone wiring should be run side by side, though segregated. Arrangement of specimen for a typical cross-connection component For connection components used above ground, the specimens are subject to a salt mist treatment for three days, followed by exposure to a humid, sulphurous atmosphere for seven days.
The protective angle afforded by an gkide rod is clearly a three dimensional concept. If the system is required to be isolated from the structure then a conductor suspended between two free standing masts may be employed.
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