Lightning and surge protection

  • Lightning and surge protection for photovoltaic (PV) systems

    Due to their exposed installation sites and large collection areas, Photovoltaic (PV) installations are at a high risk of damage due to both direct and indirect lightning strikes. Since the PV system is connected directly to the building electrical system, the subsequent damage and disruption from these surges can cause serious damage to PV installations, expensive inverters and the building electrical system. Damage is not only limited to potentially high repair costs but also loss of service and important revenue for Solar Power plants.

  • Lightning and surge protection for intrinsically safe circuits by DEHN (UK) Ltd

    In chemical, petrochemical and many industrial plants, potentially explosive areas develop frequently during the manufacturing, processing, storage, and transportation of flammable materials (e.g. gasoline, alcohol, liquid gas, explosive dust).

    Special explosion protection measures must be taken in industrial sectors where gas, vapour, fog or dust occurs during the processing or transport of flammable substances which, in combination with a mixture of air, may present a dangerous explosive atmosphere.

    Lightning currents and overvoltages in potentially explosive atmospheres

    When assessing the risk for potentially explosive atmospheres, the following lightning related ignition sources should be considered:

  • Lightning current and surge arrester for multi-pair telecom cabling

    In today’s modern world the uninterrupted use of information technology and automation equipment is taken for granted. Lightning discharges, surges and over-voltages can cause major problems to equipment resulting in physical damage, data loss and the associated cost of lost production.

  • Power supplies survive lightning strike test

    DIN-rail power supply manufacturer PULS has carried out extreme testing of its QT40 3-phase units by subjecting them to simulated lightning strikes.

  • Lightning protection - Mastering the maze of BS EN 62305

    Lightning protection - Mastering the maze of BS EN 62305

    The BS 6651 British Standard on lightning protection has existed for decades. Now, a new standard, BS EN 62305, has been published for Britain. Compared to the BS 6651’s 118 pages, 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 overview of the new standard and the consolation that, complex as the new standard may be, its key concepts are not alien, and, with relevant technical advice and support, it can be mastered

  • Lightning Protection - Combined lightning and surge arresters: spark-gaps or varistors?

    Erich H. Reuss, of DEHN (UK), discusses the potential problems associated with MOV combined arresters, and urges engineers to be aware of the limitations of these devices

    According to European Standard EN 61643-11, low-voltage surge protection devices are classified as types 1, 2, and 3. Nowhere are these discrepancies more obvious than with so-called combined arresters, where a multitude of names such as combined arrester set, type 1/type 2 combination, B-C arrester, T1+T2+T3 arrester or even BCD arrester are a recipe for confusion, leading to the situation where different products are available with parameters, protective effects and even different wave shapes which deviate from one another.

  • Lightning Protection - Out with the old, in with the new

    The introduction of BS EN 62305: Protection Against Lightning on 1 September 2008 is already having a profound impact on the industry and its customers says Colin McElhone, managing director at Omega Red Group

    Having spent the past two years preparing for the introduction of the new standard, it shouldn't really be a surprise now it's here.

    But like many in the lightning protection industry I have spent my entire working life working under its predecessor and knew it inside out. Doubtless we had all become comfortable with the old standard.

  • Overvoltage protection - When lightning strikes

    Lightning can cause significant damage to sensitive, mission-critical systems within a building if lightning protection measures are not adequate. Paul Considine of Wieland Electric explains how the risk can be aligned to the cost of protection

    With the increasing use of, and dependence on, technology in just about every business, protecting sensitive equipment is becoming ever more important. In a manufacturing or logistic operation, for example, disruption to processing or handling systems can have a catastrophic effect on productivity. Similarly, in the financial sector, server rooms are mission-critical and any failure can lead to losses of millions of pounds every hour.

  • Lightning Protection - Practical application of the BS EN 62305 Zone concept

    BS EN 62305 has given us new ways to apply concepts outlined within the standard to tackle problems with a logical, systematic approach. In BS 6651 basic surge protection was mentioned under Annex C. BS EN 62305-4 Electrical and Electronic systems within structures is a complete document dedicated to the problems, and solutions, encountered due to lightning current and induced surges. Mike Forsey, technical manager at DEHN (UK) explains

    The new standard calls for a risk assessment calculation to be carried out, part of the assessment determines if surge protection is necessary and if so what type of surge protection device, or devices, needs to be installed.

    With the increase of electrical and electronic systems being used within both business and private environments the continuing reliance, functioning and uninterrupted use of these systems is becoming essential. Equipment ranging from the basic power supply and distribution systems to specialist equipment for computer, networks, building management (BMS), telecommunications, control and security, etc now play an essential role in our lives. Damage caused by lightning and switching related events has not only a direct repair cost but also an indirect consequential cost due to down time, data re-instatement, etc.

    Using the protection principles outlined in BS EN 62305-4 the protection of such systems against surges is based on the principle of lightning protection zones (LPZs), in which the building or structure being protected is divided subject to the location of the equipment within the structure. Using this approach, suitable zones can be defined according to the number, type, immunity and sensitivity of the electrical and electronic devices or systems present within the structure. Sizes ranging from small local zones to large integral zones that can encompass the whole building can be established. At the boundary of each internal zone, equipotential bonding must be carried out for all metal components and utility lines entering the building or structure. For mains power, data, telecomm, etc this is carried out with the use of suitable surge protection devices.

    As can be seen from the diagram below a lightning current arrester, SPD Type 1,  (Waveform 10/350) is required at the interface of zones LPZ0/1 for any cable entering from a zone LPZ0A. At the boundaries of LPZ1/2 and higher a surge arrester, SPD Type 2 (Waveform 8/20) would be used.

    The same principle is used for all conductive cables entering the structure be they mains power, telecomm, data, networks or CCTV.

    Spatial shielding within the structure also forms part of the protective measures. By correct design and placing of suitable shielding the magnetic fields within the structure can be attenuated.

    Protection management
    For new buildings and structures, optimum protection of electrical and electronic systems within the structure can be best achieved cost-effectively if these systems are designed together with the building and are taken into account before its construction. For existing buildings and structures, the cost of this protection is usually higher than for new buildings and structures. If however, the LPZs are chosen appropriately and existing installations are used or upgraded, the costs can be reduced. If the risk analysis as specified in the new BS EN 62305 -2 shows that surge protection is required, this is best achieved if:
    - The measures are designed by a lightning
    protection specialist having knowledge of
    electromagnetic compatibility;
    - There is close co-ordination on all aspects of
    the work between the building experts (e.g.
    civil and electrical engineers) and the surge
    protection experts;
    - An appropriate management plan is
    adhered to.

  • Lightning protection - Fire alarm systems protected

    In a dangerous situation, emergency alarm systems (fire alarm systems or burglar alarm systems) should signal ‘actively', and remain ‘passive' in safe situations according to DEHN UK. Malfunctions of these systems (no response in case of danger, or alarm signal in case of no danger) are undesirable and expensive. False alarms sent by emergency alarm systems result in expenses, which, in the industrial countries, amount to several hundred million Euros per year. Another aspect of malfunctions is the possible direct or indirect danger to human lives. In this context, we may remember the malfunction of the fire alarm system in the tower of the Frankfurt Rhein-Main airport in 1992, where a false activation of the fire extinguishing system occurred because of a lightning strike. Within a few minutes, the air traffic controllers had to leave the control room. In this critical situation, approaching airplanes had to be redirected to other airports. Considerable delays occurred in the air traffic. False alarms of emergency alarm systems are also disturbing in another respect:
    - When false alarms accumulate, the operator can no longer rely on the system and questions the significance of the system (investment) as such.
    - The guard starts ignoring alarm messages.
    - Neighbours will be disturbed by acoustic alarms.
    - Fire-fighting forces (e. g. fire brigade) will be bound unnecessarily.
    - The activation of the fire extinguishing system causes interruptions of operations.
    - Damage is caused by not signaling existing dangers.

    All these factors cause unnecessary expenses. They can be avoided, when possible causes for false alarms are already recognised in the design stage and are eliminated by suitable preventive measures. For this purpose, the German Insurance Association (Gesamtverband der Deutschen Versicherungswirtschaft e. V. - GDV) published VdS guidelines (VdS 2095; VdS 2311; VdS 2833). One of the measures also requested in the VdS guidelines is lightning and surge protection.

    A coordinated lightning and surge protection prevents a false alarm caused by atmospheric discharges and improves the availability of the early detection of dangers and alarms. When installing comparable alarm transmission systems, for which, out of financial reasons, a VdS approval is not used (in residential building for example), the guidelines may also be used for project design and for the construction as well as for agreeing individual measures between constructors and operators. Indeed,  fire alarm systems installed nowadays have an increased surge immunity in accordance with IEC 61000-4-5 for primary and secondary wires as well as for the mains inputs. However, a comprehensive protection against damage by lightning discharge and surges can only be achieved by external and internal lightning protection measures.

    Monitoring principles
    Different monitoring principles are applied for emergency alarm systems:

    Impulse line technology
    The information from the triggering alarm device is transferred in digital form. This allows recognition of the alarm device and the exact localisation of the trouble spot (Fig. 9.9.1).

    DC line technology
    Each alarm line is permanently monitored according to the closedcircuit principle. If an alarm device is activated in the line, this line is interrupted and an alarm is triggered in the control and indication equipment. Hereby, however, only the alarm line can be identified but not the individual detector.

    Regardless of the used monitoring principle, the lines of the emergency alarm system must be integrated into the lightning and surge protection of the complete system.

    Protection recommendations
    For protection of alarm lines with dc line technology, Blitzductor CT BCT MOD BE. is recommended. It is chosen according to the voltage of the alarm lines, which is normally 12 or 24 V. Blitzductor CT BCT MOD BE is recommended to avoid having to change the loop resistance of the alarm lines too much.

    Regardless of the line topology, the outputs of the control and indication equipment, for acoustic and visual signalisation for example, should be protected by Blitzductor CT. Care should be taken to ensure the nominal current of the protective devices is not exceeded. In case of nominal currents > 1A, the company suggests a DEHNrail DR 24 FML protective device be used. (see Table 9.9.1). The control and indication unit is normally connected to an exchange line of a fixed-network operator by means of a telephone dial unit. For this application, the SPD type Blitzductor CT, BCT MOD BP 110 would be suitable. The surge protection of the power supply is important, too. For alarm systems, which are certified by the German Insurance Association, (systems recognised by VdS), the manufacturer of the alarm system should be contacted. The installations as well as the lightning and surge protection equipment have to be set up in accordance with VdS 2095, VdS 2311 or VdS 2833.

    Conclusion
    A distinct increase in the operational reliability of these systems can be reached with specific lightning and surge protection of alarm systems, including the prevention of false alarms when no danger exists, and the prevention of costs arising from this. This allows effective damage limitation by informing the auxiliary personnel reliably., counteracting potentially catastrophic conditions including danger to human lives and pollution of the environment.
    In the event of injuries to persons or environmental damage, the operator of a plant is liable first. This comprehensive responsibility for security can normally be expected from managers or executives of a company. However, in the legal sense, an operator of a plant is a technical layman, who is not able to assess the potential risk involved in a technical solution. Therefore, skilled persons as suppliers of technical solutions must ensure in each individual case, the solutions offered correspond to the actual requirements.

    Regardless of the fact, whether fire alarm systems are VdS-approved systems or not, they should be furnished with a surge protection.

  • Lightning protection - Engineers field FAQs

    The introduction of the new and more complex standard BS EN 62305:2006 Protection against Lightning has led to many new questions and the resurfacing of several ‘old chestnuts'. We look at a few of the most frequently asked questions fielded by Furse engineers

    My building has stood for 100 years, and has never been hit.  So there is no chance of it being struck now!

    Not being hit by lightning in the past has no bearing on being struck in the future. The probability of a strike and whether protection should be fitted will be shown by carrying out a risk assessment. York Minster was around 600 years old when it was ‘eventually' struck by lightning in 1984, causing extensive irreplaceable damage. Remember a direct strike to the structure is not even necessary for lightning to cause damage through fire, electric shock or electronic systems failure.

    I have an air finial on the tallest part of the building and a down conductor, so that should be adequate?

    This is unlikely to give adequate protection in accordance with BS EN 62305 which calls for a full Faraday Cage, comprising a number of conductors on and around the building.

    My building has reinforced concrete columns. Can I use these columns as down conductors?

    Yes, provided you ensure the electrical continuity of one or more reinforcing bars in each column. Where sections of reinforcing bar overlap, they should be welded or clamped together, or overlapped by at least 20 times their diameter and securely bound for the entire length of the overlap.

    How do I know if my building needs lightning protection and, if so, what level of lightning protection system (LPS) is required?

    There's no intuitive way of doing this - you need to carry out a risk assessment in accordance with BS EN 62305:2006 Part 2. The risk assessment in BS EN 62305-2 is much more detailed and has many more parameters than the assessment contained in BS 6651. There are software packages available that can help. Furse's bespoke risk assessment software package is called StrikeRisk. It has just been updated to version 5, and a free trial version is available to download from its website - www.furse.com

    I have looked at the number of parameters required to carry out a risk assessment, but cannot find all the information. What should I do?

    The risk assessment carries default values, which can be used where accurate information is not available. However, these values are conservative, so you should try and obtain as much accurate information as possible.

    Why is there now so much emphasis on protection of sensitive electronic systems? This wasn't a requirement of BS 6651.

    The protection of electronic systems was covered in Appendix C of BS 6651, and although this was an informative annex, the philosophy is broadly similar to that of the new standard. Our increasing reliance on electronic systems means that damage or downtime can have serious financial and operational consequences and hence their protection is reflected in the single risk assessment of the new standard..

    I have a lightning conductor system on my building, so will this protect my electronics within the building?

    No, this will protect the structure itself but not the electronics within it. You therefore need specialist surge protection to prevent equipment damage from LEMP (lightning electro-magnetic impulse). BS EN 62305 focuses on coordinated SPDs (surge protection devices), where the locations and LEMP handling attributes of a series of SPDs are coordinated to nullify the conducted LEMP effects - thereby protecting equipment within their environment.

    Is it adequate to put surge protection on the main electrical incomer only?

    Although protection of the main incomer is certainly recommended, other services should be considered for protection against transient overvoltages (surges). For example, a lightning strike up to 1km from a building can transfer huge voltages onto overhead or underground cables - like data or telephone lines - through inductive or resistive coupling. Once transferred to the cable, transients will flow along it, seeking a path to earth and damaging any electronic components they encounter.

    I am fitting an LPS to a building, which contains no sensitive electronics systems. Do I still need to fit Type 1 (equipotential bonding) SPDs?

    Yes. Type 1 SPDs (for mains power supplies) and Category D SPDs (for data/telecom lines) form an integral part of the equipotential bonding requirements for an LPS. They are needed to prevent partial lightning currents from causing dangerous sparking and the possibility of a fire or electric shock hazards. Type 1 SPDs are not designed to protect equipment, but form the first part of a coordinated SPD set further consisting of Type 2 and 3 SPDs.

  • Lightning fast calculations

    Furse's popular StrikeRisk software makes lightning risk assessments lightning fast. A trial version of the new StrikeRisk v5 is available free of charge from the Furse website.

    StrikeRisk has been specifically developed for engineers, architects and contractors who have to carry out the risk calculations demanded in BS EN 62305-2:2006 Risk management.  The software interface helps users complete BS EN 62305-2's complex and laborious risk calculations in minutes rather than the hours it would take doing them by hand.

    With StrikeRisk, an engineer can carry out and view multiple risk assessments under the banner of a single project, build new projects from previously saved cases and create templates for standard cases. StrikeRisk enables users to split a structure into multiple zones to highlight high risk areas, as well as considering multiple cables connected to the structure and multiple remotely connected structures.

    In addition StrikeRisk v5 offers multi or single user licensing, an easy to use interface, excellent security options and reporting facilities.


    Furse
    Tel. 0115 964 3700
    http://www.furse.com/

  • Lightning protection - Getting the right surge protection

    The extensive use of electronics within industrial processes and buildings has meant  protection against the effects of voltage surges is no longer an option but has become a necessity. Lightning produces an extremely large quantity of pulsed electrical energy, which means surge protection devices designed to limit transient overvoltages need to be correctly specified to ensure they are effective. Tom France from Schneider Electric looks at the selection considerations, taking into account location and the types available

    As business operations become increasingly sophisticated, the use of technologies such as LCD screens, computer networks, data servers and industrial equipment such as programmable logic controllers, means that protection against the effects of voltage surges is crucial.

  • Upgraded lightning protection for remote corrosion monitoring

    Abriox has upgraded the lightning protection on its remote corrosion monitoring solutions for pipelines, with the help of the lightning test consultancy services of Cobham Technical Services. The degree of protection of the system against high energy surges has been substantially enhanced by a development exercise incorporating advice on the nature of coupling between lightning power surges and ground-based equipment, and characterisation studies including destructive testing.

    The protection has been implemented on Abriox's Merlin cathodic protection (CP) monitor. This telemetry-based instrument is one of the most widely used field devices for remotely monitoring the anti-corrosion CP systems that are installed on pipelines, storage tanks and other buried metal infrastructure used in onshore oil and gas networks.

    "Pipelines are a significant attractor for lightning, and in some regions of the world strikes can occur frequently. We've always had lightning protection on our corrosion monitor, but the only feedback we ever got on how it performed in the real world tended to be when a burnt-out unit arrived back from the field," says Jason Hanlon, technical director of Abriox. "How much energy was present, what the shape of the energy surge was, whether it arrived directly or indirectly remained a mystery - and we decided it would be a good idea to better understand the risk by talking with lightning experts."

    Abriox has its design centre in the UK, and after investigating the high voltage testing market, selected UK-based Cobham Technical Services, because its lightning unit is one of a tiny number of organisations in the world that specialise in lightning testing and consultancy and is able to give practical advice, rather than simply testing against standards.

    An initial review considered the particular installation conditions and environments of the Merlin CP monitor, and a typical catastrophic field failure. A destructive test at Cobham's test facility in Abingdon was performed. It became clear the corrosion monitor was most likely dealing with power surges that arrived following direct strikes on the pipeline itself, or the supply to the electrical rectifiers that provide the impressed-current cathodic protection system. Unlike some of the areas that Cobham works in - particularly aircraft protection - there are no standard lightning test waveforms for this type of nearby strike to ground-based equipment, but that did not prevent Cobham from creating a representative waveform specifically for this testing purpose.

    The destructive test exercise also demonstrated to Abriox that some of the external lightning surge protection devices originally selected for use with Merlin did not actually perform in the way the manufacturer's datasheet indicated. Although other aspects of the Merlin design provided a good degree of protection, the Abriox designers sought further improvement.

    After the exercise, Abriox gained a better understanding of the nature and energy levels of lightning-related power surges, and decided to re-engineer the system to increase the protection level. This exercise involved both uprating the surge protection circuitry, using different components and changing the physical layout of parts of the embedded electronics system.

    To speed the design phase, Abriox constructed its own simple low-power generator that could provide a high voltage pulse, to test switching times and clamping characteristics. However, when the final protection design was settled on, Abriox took a monitor to Cobham to fully characterise its performance against lightning pulses.

    Cobham subjected the equipment to increasing levels of lightning strikes using a range of pulse shapes and durations that represented the kind of surges that would be experienced in typical installation scenarios. The revised protection worked perfectly, and continued to operate successfully beyond its target energy level protection rating corresponding to a 12 kA transient waveform. Cobham used a 30 kA-rated generator to test the equipment, and in the very final test step, the strike energy was increased to the maximum. Although this destroyed the front-end protection circuitry, the Merlin monitor itself survived and continued to function.

    "With Cobham's help, we now know exactly what our lightning protection system is capable of," adds Jason Hanlon of Abriox. "It's impossible to protect against every conceivable lightning strike, but we know that our equipment will be resilient when faced with the majority of the real-world energy surges that could be encountered."

    "This particular project was very interesting. Our understanding of the nature of the lightning threat means that we were able to simulate the type of waveform expected by Abriox's monitor in the field," says Dan Brown of Cobham Technical Services. "This type of pipeline installation makes it highly likely that power surges arrive indirectly, from the pipe or power supply, making it important to consider protection for the design as a whole - rather than just the system inputs. It's easy to blow up a device in our lab; what's more of a challenge is to do it in a representative way."

     

  • Lightning protection - Pre-empting the strikes

    Many organisations seeking to lower their carbon footprint are tapping into solar energy using photovoltaic systems, which are highly vulnerable to lightning damage. Ian Langeveld, UK and Ireland sales manager with Wieland Electric, discusses the importance of suitable protection for these systems

    As technology has become an integral part of everyday life, measures to protect our devices and the systems that serve them have also increased in importance. Indeed, in some cases, protecting these systems has become critical to the business’s ability to operate. Thus, for example, protection against the damage that can be caused by lightning strikes is now just as important for many businesses as securing their buildings against intruders.

    Now, with the growing use of photovoltaic (PV) arrays to harness solar energy there is an additional area to be considered when it comes to protection strategies. And with feed-in tariffs encouraging electricity generation from renewable energy sources this is an area that will continue to grow.

  • Be prepared for lightning

    Be prepared for lightning

    Atlas urges contractors, engineers and manufacturers to undertake its Lightning Protection Designers Accreditation Assessment.

    Atlas, the Association of Technical Lightning and Access Specialists, says lightning accounts for 27% of storm deaths annually worldwide, which is only slightly less than the 31% of deaths caused by tornadoes and hurricanes combined. The association says there could be as many as 5,000 lightning-related injuries each year.

    Sixty individual operatives have already taken and passed the assessment, which provides preparation for the next level of compliance in Europe (CENELEC), which will supersede British Standard BS 6651 lightning protection in the UK.

    The assessment does not take up valuable work time and costs just £100 plus Vat per application. It is only open to existing Atlas members and demand for places appears to have been high.

    Atlas is the national representative employers’ organisation for companies engaged in the steeplejack, lightning conduction, earthing design, installation, demolition, restoration and maintenance of high rise and historic buildings, industrial chimneys, churches, off-shore rigs, and other tall structures.

    For more information, call 0115 955 8818.

  • StrikeRisk for lightning calculations

    Furse's popular StrikeRisk software has been improved, making lightning risk assessments lightning fast. A trial version of the new StrikeRisk v5 is available free of charge from the Furse website.

    StrikeRisk has been specifically developed for engineers, architects and contractors who have to carry out the risk calculations demanded in BS EN 62305-2:2006 Risk management.  Its improved interface helps users complete BS EN 62305-2's complex and laborious risk calculations in minutes rather than the hours it would take doing them by hand.

    With StrikeRisk, an engineer can carry out and view multiple risk assessments under the banner of a single project, build new projects from previously saved cases and create templates for standard cases. StrikeRisk enables users to split a structure into multiple zones to highlight high risk areas, as well as considering multiple cables connected to the structure and multiple remotely connected structures.

    In addition to an improved user interface, StrikeRisk v5 offers expanded licensing and security options, and a greater reporting facility.

    For more information or a free 15-day trial, please visit our website, http://www.furse.com/ or call us on 0115 964 3700.

  • Overvoltage - When lightning strikes

    Lightning can cause significant damage to sensitive, mission-critical systems within a building if lightning protection measures are not adequate. Paul Considine of Wieland Electric explains how the risk can be aligned to the cost of protection

    With the increasing use of, and dependence on, technology in just about every business, protecting sensitive equipment is becoming ever more important. In a manufacturing or logistic operation, for example, disruption to processing or handling systems can have a catastrophic effect on productivity. Similarly, in the financial sector, server rooms are mission-critical and any failure can lead to losses of millions of pounds every hour.

    Interference-free operation, therefore, is crucial and the integrity of these systems has to be maintained even under relatively extreme circumstances such as thunderstorms. And while safety devices such as fuses will protect against excess current, they are ineffective against the high voltage transients and short-duration spikes that lightning can generate on power supply lines.

    This, of course, is all fairly obvious and forms the basis of the lightning protection systems that are incorporated into many buildings. However, despite the clear dangers and the critical nature of many systems, the high volume of insurance claims for lightning damage indicates that many building operators are failing to ensure appropriate lightning measures are taken.

    This situation is becoming of increasing concern because climatologists are predicting that climate change will bring about more extreme weather conditions, with an anticipated increase in the frequency and intensity of thunder storms in the UK and other areas of northern Europe.

    It's fairly reasonable to assume that the key reason for the lack of protection on many buildings is that businesses often seek to achieve a balance between the cost of installing lightning protection and the risk of suffering lightning damage. There may also be a feeling that any damage will be covered by insurance. However, while insurance may cover the tangible damage it can't restore the reputation of a company that has let its customers down by not safeguarding its systems adequately.

    A sensible compromise is to adopt a zone concept for lightning protection - as described in IEC 62305-4 (DIN EN 62305-4, DIN 0185-305-4). This enables planners, builders and owners to align the protective measures they adopt with the risk levels to the business of damage occurring. In this way, all relevant devices, plants and systems are afforded a level of protection commensurate with their importance to the business.

    For all of these reasons electrical engineers need to be aware of the options open to them and the requirements of the relevant standards. To that end, lightning strikes can be divided into two key types - direct strikes and remote strikes.

    Direct or close-up lightning strikes are lightning strikes into the lightning protection system of a building, in close proximity to it, or into the electrically conductive systems implemented in the building (e.g. low-voltage supply, telecommunications, control lines).

    Remote lightning strikes are lightning strikes that occur far away from the object to be protected as well as lightning strikes into the medium voltage overhead system or in close proximity to it, or lightning discharge from cloud to cloud.

    In addition to a lightning protection system in the building, additional measures for an overvoltage protection of electrical and electronic systems are required in order to safeguard the continuous availability of complex power engineering and IT systems even in the case of a direct lightning strike. It is important to consider all the causes for overvoltages.
    In terms of lightning protection, BS EN 62305:2006 (Protection against lightning) advises provision of a conventional or Faraday Cage lightning protection system and these systems can be divided into external and internal types.

    An external lightning protection system will typically comprise an air termination system, down conductors and an earth termination system. Clearly, all of these elements need to connected effectively so that if lightning strikes the building the current discharge is conveyed safely away and damage to the building is minimised. This is achieved by ensuring that connection components comply with BS EN 50164.

    An internal lightning protection system is designed to eliminate the risk of dangerous sparks inside the building or structure, following a lightning strike. Such sparking could be caused by current flowing in the external lightning protection scheme and sparking over to metallic elements inside the building. Or this could happen if current flows through any conductive elements on the outside of the building.

    The danger of sparking, therefore, is minimised by creating a sufficient distance between metallic parts or by carrying out appropriate equipotential bonding measures. Equipotential bonding will ensure that no metallic parts are at different voltage potentials, so there is no risk of sparking between them. This can be realised either through bonding between conductive elements or the use of surge protection devices. The latter is particularly appropriate where direct connection would not be appropriate, such as between power and communication lines.

    As noted above, the commercial reality is that these measures need to be introduced in relation to the level of risk and the criticality of the processes or systems to the business. This is the basis of the zone concept for lightning protection, as it effectively divides a building into different risk zones. The zones for lightning protection are defined in Table 1
    In our experience, this zoned approach strikes the right balance between capital outlay and operational risk and proves of great benefit to building operators who are trying to strike the right balance. It is also a very effective way for electrical designers to add value for their customers.

  • Lightning protection - Ignorance is no defence!

    Last August saw the long awaited arrival of the new British Standard for lightning protection, BS EN 62305, replacing the now obsolete BS 6651. It has changed, and will continue to change, the way lightning protection is understood, planned and implemented. Yet despite extensive publicity, widespread confusion across the industry remains, particularly among main contractors. As a result some Atlas members have lost out on contracts, even though their proposed solution was the only compliant option explains Fiona Lindsay at Atlas

    The past year has been a huge learning curve for the entire industry. Literally thousands of operatives, apprentices and consultants now have to possess some, if not full, comprehension of this new standard. Its arrival has changed how the industry operates forever! For the past three years a dedicated Atlas team has worked tirelessly to disseminate and educate the industry about the fundamental changes, additions and implications of BS EN 62305. What has become apparent is Atlas members who undertook the special training workshops are a cut above the rest.

    The complex risk assessments that are now compulsory under the new standard are extremely time consuming but intrinsic to the whole process. However, several members have reported many contractors still appear to be unaware that these risk assessments are a mandatory requirement and are therefore still accepting quotations from non Atlas members who are not working to the new standard. Colin Clinkard from Best said: "We are extremely happy our LC designers and estimators have passed the Atlas accreditation, however there still needs to be a huge push to ensure that main contractors understand the repercussions of not using a BS EN 62305 accredited lightning protection company."

    This point is further highlighted by another Atlas member, Edward Wilson & Co, who has found many contractors and architects are still requesting quotations from the company based on the old BS 6651. In the current economic climate, contractors are understandably looking for the best price. This, coupled with their lack of knowledge on the extreme differences between the old and new standards means that they are often commissioning unsuitable work that is not compliant. Atlas members are dedicating a lot of time in an attempt to educate the contractors they work with about the BS EN 62305, and it is beginning to have a positive effect. However, with approximately two thirds of contractors and architects clearly not understanding the new standard, it is very frustrating and inconvenient to have to teach them what BS EN 62305 is all about every time they tender for new business.

    Although there are inevitably issues surrounding BS EN 62305, all Atlas members believe the new standard is a positive thing for the industry. Atlas member, John Ashmore from Protectis said: "The next step must be to set up training workshops for engineers and architects. It's as simple as this; unless they understand how the new standard works and the huge benefits that it gives them, inadequate lightning protection will continue to be offered to clients who will then find that their buildings are non-compliant."

    Fellow member, Andy Richie agrees. His company, Lightning Protection Services has noticed a lot of large projects that were originally planned before the new standard's implementation are still being built now with out-of-date protection. Jason Harfield of Orion has also observed the new standard is being ignored with specified separation distances not being adhered to. Orion has put all their employees through the Atlas design course for the BS EN 62305 and feel the whole industry must follow suit, if only to put an end to the ignorance.

    Overall, everyone agrees more education on the new standard needs to be provided to the construction industry as a whole. Atlas is still the only organisation to offer comprehensive training. The National Construction College offers NVQ Level 2 for apprentices but this is only a basic introduction. Like it or loath it, the arrival of BS EN 62305 has split the industry. Lightning protection is now recognised as an extremely skilled profession. The new standard has clearly started to separate out the professionals from the cowboys!

    Case study: Red turned green

    Scout Moor Wind Farm, (the largest onshore wind farm in England), consists of 26 wind  turbines situated on the moors of North West England between Rawtenstall and Rochdale with the Rossendale Way running through the heart of the site. When running at full capacity, the farm generates 65MW of electricity, providing enough power to meet the average needs of 40,000 homes. To ensure continuous and reliable electricity generation in such an exposed location, the site required the installation of extensive earthing and lightning protection systems to protect it from the potentially devastating effects of a lightning strike. McNicholas awarded the contract to Omega Red Group - one of the UK market leaders in earthing and lightning protection.

    In the early stages of the project, Omega personnel conducted soil resistivity surveys at each of the turbine locations, and at the substation situated approximately a mile away, to enable a detailed design to be undertaken. This would not only ensure the safety of the structures themselves, but would also safeguard the general public against the hazardous touch, step and transfer voltages that can occur when lightning strikes or when power system faults occur.

    The remote location of the wind farm combined with unpredictable and often inclement weather conditions (including thick fog, snow, ice, torrential rain and gale force winds) provided additional challenges throughout the project. During the installation, a few potential issues were encountered in obtaining the requisite resistance values at some of the turbine locations, largely due to the ground conditions varying from marsh bogs to solid rock. However, the proactive approach and technical expertise of Omega's onsite engineers and operatives soon ensured that these issues were resolved without compromising the construction programme.

    At the end of the construction and installation phase, Omega was further tasked with carrying out the overall test of the earthing and lightning protection systems on both the substation and turbine sites to confirm their compliance with all statutory requirements. Due to the large footprint of the site, the test leads were required to be run out in excess of 2 kilometres - including across a waterfall - to obtain an accurate set of test results - just another small challenge for the Omega engineers to overcome!

    Because climate change is now widely recognised as one of the most important global issues, and reducing the amount of greenhouse gas emissions is a vital element in limiting the effects of climate change, Omega is committed to working within the renewable energy market, using its expertise, technical competence and extensive experience to overcome the very specific challenges this market presents.

    "The sheer size of wind turbines along with the isolated locations upon which they are constructed renders them vulnerable to lightning strikes. Without adequate earthing and lightning protection systems they are more likely to suffer the detrimental effects of a lightning strike. We are extremely happy to be involved in the success of wind farms across the UK and to use our expertise in the support of this growing, environmentally- friendly industry".

    Colin McElhone, managing director, Omega Red Group

    Case study: Straight sets

    For almost 35 years R. C. Cutting & Co. has been involved with the All England Lawn Tennis  Club (AELTC) both in new installations and the ongoing maintenance surrounding their world famous Championship in June each year.

    Most recently have been the challenging works to Centre Court, where a new retractable roof has been incorporated over a three year construction period. The continued use of the playing surface during the Championships was always a factor and the re-development works had to be scheduled around this.

    Now complete, the roof can be closed and the temperature and humidity controlled dependant on the number of spectators, thus ensuring that play can continue whatever the weather.

    For those that remember, the 1996 Championship was delayed hugely by bad weather and the crowds were frustrated by the conditions and delays. .

    The lightning protection system, originally installed by Cuttings in 1992, has been enhanced and the steel supporting structure of the new retractable roof was incorporated giving particular regard to the many moving parts!

    The closing roof was used during the 2009 Championship and allowed play to continue well into the evening, creating the latest finishing game in the history of the event.

    Originally built in 1922, Centre Court held 13,810 spectators in 2008, increasing to 15,000 for the 2009 Championship by adding six rows of seats to the upper tier on the east, north and west sides.

    An inscription above the entryway to Centre Court reads "If you can meet with triumph and disaster / And treat those two imposters just the same" - lines from Rudyard Kipling's poem If.

     

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