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Lightning Protection - Mastering the Maze of BS en 62305

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  10/21/2014Lightning protection - Mastering the maze of BS EN 62305http://www.electricalreview.co.uk/features/5004Lightning_protection_-_Mastering _the_maze_of_BS_EN_62305.html1/5 Lightning protection - Mastering the maze of BSEN 62305 The BS 6651 British Standard on lightning protection hasexisted for decades. Now, a new standard, BS EN 62305, has been published for Britain. Compared to the BS 6651’s 118pages, the 475-page BS EN 62305 is daunting. Expanding on an article in the May issue of Electrical Review John Sherlock of Furse (pictured right), offers an ov erview of  the ne w standard and the consolation that, complex as the new standard may be,its key concepts are not alien, and, with relev ant technical adviceand support, it can be masteredBS EN 62305 came into force on 1 September 2006. At the moment, it runs concurrently with BS6651, but ultimately BS 6651 will be withdra wn and BS EN 62305 will be the only recognisedstandard by the end of August 2008. The new  standard consists of four parts: BS EN 62305-1 : Part 1 General principlesThis is an introduction to the other parts of the standard. BS EN 62305-2 : Part 2 Risk managementBS EN 62305-2 specifically deals with making a risk assessment, the results of which define the levelof Lightning Protection System (LPS) required. It includes many more parameters than BS 6651 w hich devotes 9 pages including figures, whilst BS EN 62305-2 contains some 153 pages. BS EN 62305 contains a series of National Annexes, from which individual countries, like the UK,have used their own interpretation and perception of risk to compile parameters for certainelements of the risk assessment. The first stage of the risk assessment is to identify the types of loss that a structure and its contentscan incur. There are four types of loss defined in BS EN 62305, compared with the one – risk of death/injury – considered in BS 6651. These risks are:l R1 – loss of human life l R2 – loss of service to the publicl R3 – loss of cultural heritage (ie. of historic  buildings or monuments)l R4 – loss of economic value, considers the cost of the physical loss of equipment. It does not,however, take into account the economic value of consequential losses from system downtime. Once the applicable types of loss have been identified, a tolerable risk (RT) for each can be looked upin a table contained in the National Annexes. The actual risk (R) is then arrived at through a seriesof calculations, using formulae in the standard and including various weighting factors. If the actual risk (R) is lower than the tolerable risk (RT), then no protection measures are needed.If R is greater than RT, then protection measures, as determined from the tables given in thestandard, are required. A series of trial and error calculations is then required in order that a THURSDAY, 12 JULY 2007 00:00  RELATED ARTICLES Protective conductor guard - 15.03.13Low levels of let through voltage - 24.09.10Lightning protection - Getting the right surge protection- 02.07.10New VPU surge voltage protection devices - 03.12.12Strike action - 02.11.12  MOST POPULAR Release your energysavings potential withPowerstar A New Data Centre atMMU JTL opens new AM2 facility at BirminghamCentre of Excellence  POST: 20.10.14 New electrotechnical skills organisation formed  POST: 20.10.14 Steady second quarter for electrical contractingbusinesses  POST: 20.10.14  AIT PIMs integrates open standard assetmanagement tags  POST: 16.10.14 ETI seeks partners for a new energy marketdesign scenarios project  POST: 07.10.14 LATEST NEWS MOST READCOMMENTS NEWS PRODUCT NEWS FEATURES ER TV DIRECTORY EVENTS MAGAZINE CONTACT SUBSCRIBE JOBS Last update 02:17:04 PM GMT Headlines:10212014SEARCH Steady second quarter for electrical contracting b...  10/21/2014Lightning protection - Mastering the maze of BS EN 62305http://www.electricalreview.co.uk/features/5004Lightning_protection_-_Mastering_the_maze_of_BS_EN_62305.html2/5 sufficient level of lightning protection can be defined. This result decides the choice of lightningprotection system and lightning electro magnetic impulse (LEMP) protection system (LPMS). BS EN 62305-3 : Part 3 Physical damage to structures and life hazardsThe third part of the new standard relates directly to the main body of BS 6651, but there aresignificant differences between the two. BS EN 62305- defines four lightning protection levels (LPLs) based on probable minimum andmaximum lightning currents. These LPLs directly equate to classes of lightning protection systems(LPS).The new standard uses the class of LPS to define several attributes of the LPS. For example,consider the mesh sizes for an air termination network and spacing of down conductors in BS EN62305-3:Class of LPS/ Mesh size (m)/ Down conductor specing (m)I/ 5 x 5/ 10II/ 10 x 10/ 10III/ 15 x 15/ 15IV/ 20 x 20/ 20This compares with BS 6651’s two mesh sizes (20m x 10m and 10m x 5m) and two down conductorspacings (10m and 20m).In BS 6651, a mesh arrangement was the commonly used layout for the air termination network.However, BS EN 62305-3 details the use of air rods or finials, catenary or suspended conductors ora meshed conductor network, in any combination. The new standard also includes three methods for determining the position of the air terminationsystem:l The rolling sphere method (whose radius also depends on the class of LPS)l The protective angle method (a mathematical simplification of the rolling sphere method)l The mesh method As with BS 6651, the new standard recommends a single integrated earth termination system for astructure. In BS 6651 a system was used where each down conductor was attached to an earthelectrode. Whilst BS EN 62305-3 broadly follows this pattern in its Type A arrangement of earthelectrodes, it adds a Type B arrangement. This is essentially a ring earth electrode that is sitedaround the periphery of the structure and is in contact with the earth for at least 80% of its length.BS EN 62305-3 contains extensive sections, with detailed explanations on the reasons for, andmethodology of, equipotential bonding. It requires the bonding of all metallic services to the mainequipotential bonding bar. Where the services have ‘live’ cores, like power or telecommunicationscables, then a suitable surge protection device (SPD) should be used. BS EN 62305-3 expands on BS 6651’s data regarding the choice of LPS components and conductors, with tables relating to sizes and types of conductor and earth electrodes. It also specifically requiresLPS components to meet the testing regimes defined in the BS EN 50164 standard, whereapplicable. BS 6651 recommends the inspection of any LPS annually. BS EN 62305-3 goes further, categorisinginspection into visual inspection, complete inspection and critical systems complete inspection, whose frequency depends on the LPL in force. BS EN 62305-4 : Part 4 Electrical and electronic systems within structuresThis part contains one of the most critical differences between the two standards. In BS 6651, theprotection of electronic equipment is only included in an informative annex. In BS EN 62305, it is anintegral part of the standard - Part 4. Structural lightning protection cannot now be considered in isolation from transient overvoltage or surge protection. The single risk assessment of Part 2 dictates whetherstructural and/or lightning electromagnetic impulse (LEMP) protection is required. From that risk assessment, a structure may need both a structural LPS and a fully co-ordinated set of surge New prefabricatedsolutions are changingthe data centre marketAct quickly and savemoney    10/21/2014Lightning protection - Mastering the maze of BS EN 62305http://www.electricalreview.co.uk/features/5004Lightning_protection_-_Mastering_the_maze_of_BS_EN_62305.html3/5 Tweet 0  0 0 Quote 0 protection devices (SPDs) or just overvoltage protection alone.  Whilst BS 6651 recognises a concept of zoning in Annex C (location categories A, B and C), the new standard defines the concept of lightning protection zones (LPZs). This consists of two externalzones, LPZ 0A and LPZ 0B, and typically two internal zones, LPZ 1 and LPZ 2. LPZ 0A is exposed tofull current and full magnetic field and LPZ 0B to partial/induced current and full magnetic field.LPZ 1 sees limited induced current and damped magnetic field whilst LPZ 2 has a further reductionof induced current and further damped magnetic field. Successive zones are therefore characterised by significant reductions in LEMP severity, achieved through a combination of protection measuressuch as bonding, shielding and the use of SPDs. Protection levels within a zone must be co-ordinated with the immunity characteristics of theequipment to be protected, ie, the more sensitive the equipment, the more protected the zonerequired. The existing fabric and layout of a building may make readily apparent zones, or LPZtechniques may have to be applied to create the required zones. When applying bonding, shielding and SPDs, technical excellence must be balanced with economicnecessity. For new builds, bonding and screening measures can be integrally designed to form partof the complete lightning protection measures system (LPMS). However, for an existing structure,retrofitting a set of co-ordinated SPDs is likely to be the easiest and most cost-effective solution.SPDs also provide additional protection over bonding and shielding measures through protection in both common and differential modes. This ensures equipment is not only protected from damage but also remains operational during lightning activity.BS EN 62305-4 emphasises the use of co-ordinated SPDs for the protection of equipment. Thissimply means a series of SPDs whose locations and LEMP handling attributes are co-ordinated insuch a way as to protect the equipment in their environment by reducing the LEMP effects to a safelevel. So there may be a heavy duty lightning current Type I SPD at the service entrance to handlethe majority of the surge energy, plus downstream overvoltage SPDs to protect terminal equipment. Appropriate SPDs should be fitted wherever services cross from one LPZ to anotherConclusionSo, this brief overview of the new BS EN 62305 lightning protection standard clearly demonstrateshow it is more complex and exacting than its predecessor. However, the key principles are wellestablished and pretty familiar to all. Moreover, established suppliers of lightning protectionsolutions are now offering a wealth of quality support tools. These include risk assessment softwareto automate the complex and repetitive risk calculations, new technical literature, training seminarsand face-to-face assistance.BS EN 62305 will take some time for people to fully interpret and comprehend, but by using theresources available, the issues they may initially encounter certainly can be mastered. John Sherlock sits on the British Standards Institute’s GEL81 technical committee for lightningprotection, the TC81X lightning protection committee for CENELEC, and the IEC’s TC81 technicalcommittee for lightning protection.  Comments   #14  Steve Redpath   2014-08-11 15:09 Quoting Leigh Dale: I am currently a qualified electrician in a dieing industry due to the current climate. I am really  wanting to get into testing and inspecting of lightning protection and take the correct route in industry demands. I have researched what qualifications I need but I can not find anything anywhere. Cananybody help me or point me in the right direction please? Many thanks Leigh Hi LeighOur company offer lightning Protection trainiong courses for further details go to www.trans-euro.co.uk #13  Marc Pilkington   2014-04-15 11:25 Quoting Andy: 1 RecommendShare2 1 2  10/21/2014Lightning protection - Mastering the maze of BS EN 62305http://www.electricalreview.co.uk/features/5004Lightning_protection_-_Mastering_the_maze_of_BS_EN_62305.html4/5 Quote 0 Quote 0 Quote 0 Quote 0 Quote 0 Quote +1 Quote +2 Quote 0 Quote LPS telecommunications, recommended a single integrated earth conductor, please can you explain,does it mean all rods structures are 'meshed' together. Hi Andy, the recommendations given in BS EN 62305 are based heavily upon being able to achieve asmuch equipotential bonding as possible such that, in the event of a strike, all earthed equipment reachesthe same electrical potential and lessens the risk of secondary sparking. Section 5.4.1 of BS EN 62305-3states that a single earth-termination system is preferable for all systems within a building, whether thosesystems be lightning protection, power or telecommunications. In a simple system, you would have asingle main earth bar to which all electrical and electronic systems are connected to along with a bondfrom the lightning protection system, other systems may be more complicated than this but they should,ideally, come back to a single point. #12  Andy   2014-04-15 07:29 LPS telecommunications, recommended a single integrated earth conductor, please can you explain,does it mean all rods structures are 'meshed' together. #11  Alan M Dransfield   2013-04-15 17:55 The biggest hospital in the SW does not have any Lightning Risk Assessment because they claim theyhave an extensive LPS in place.I refer to the Exeter RDE HospitalI do not accept that having a LPS negates the requirement for LPS.Indeed, if the RDE had a LRA in place they would have known their installed LPS is sub-standrad #10  Alan M Dransfield   2013-04-15 15:28 My Local PA's in Devon have confirmed to me in writing they need not undertake any Lightning Risk Assessment because they have installed Lightning Protection. I feel this is foolish because the fact theyhave installed LPS that does not negate the need for LRA.They have also installed a brand new bridge over the M5 WITHOUT LPS or LRA. #9  Elinore Mackay   2013-03-14 16:20 LeighPlease email me your details to elinorem@electricalreview.co.uk and I will ask someone to contact you.Elinore MackayEditor  #8  Leigh Dale   2013-03-14 16:16 I am currently a qualified electrician in a dieing industry due to the current climate. I am really wanting toget into testing and inspecting of lightning protection and take the correct route in industry demands. Ihave researched what qualifications I need but I can not find anything anywhere. Can anybody help meor point me in the right direction please? Many thanks Leigh #7  Marc pilkington   2012-08-31 07:55  A point to keep in mind is that of the social and political pressure of providing protection to thosestructures which are viewed as being more valuable than others such as schools or hospitals. Whilst therisk process in part 2 of BS EN 62305 does not make any distinction between the social 'value' of youngor ill people there would be a far higher degree of public pressure should a building of this type be struckand a loss of life result. It is for this reason that these structures are almost always considered for lightningprotection evaluation with a system occasionally being specified regardless of the risk assessmentresults. #6  Marc pilkington   2012-08-31 07:50 BS EN 62305 does not enjoy the same legal backing as standards such as BS 7671 the wiring regs does in that there is no legal requirement to consider lightning protection for any structure regardless of its use. The onus of providing protection falls entirely on the owners of that building and what they want toachieve in terms of protection to life, electronic equipment and cultural heritage protection. Pressure toproduce a system complying with the current version of BS EN 62305 (at the time of writing, parts 1,3 &4are at 2011 version whilst part 2 is still at 2006) usually comes from the insurance company responsiblefor covering the structure and its contents. (cont in next post) #5  Alan M Dransfield   2012-08-27 05:34 The BS-EN 62305 is most clear about the technical requirements for a proper Lightning ProtectionSystem(LPS) but what is unclear to me after reading the article is, WHO IS THE OVERSIGHT BODYFORCOMPLIANCE.e.g. if a refinery or a public building was struck by lightning and resulted in deaths or injurycould or would the HSE proecute. Is the BS-EN 62305-2006 include in any HSE statutory act Refresh comments listRSS feed for comments to this post  Add comment 1 2
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