IMPACT OF LIGHTNING ON BUILDINGS AND ITS REMEDIAL MEASURES 1. INTRO INTRODUC DUCTIO TION N 1.1.
The Phenomenon of Lightning
Thunderstorms develop when ground heat creates a hot rising current of air. This air gradually cools until it condenses into small cumulus clouds. The cumulus continues to grow vertically until it eventually becomes a storm cloud c loud or cumulonimbus. These atmospheric conditions lead to the creation of electric charges resulting from collisions between water, hail and ice particles of different sizes. There are charges separation inside the cloud, with a negative charge at the bottom of the cloud and a positive charge at the top. The centre of the negative charges is usually at the base of the cloud due to the movement of electrons through the heavier drop drople lets ts and and hail hailst ston ones es,, whil whilst st the the cent centre re of the the posi positi tive ve charges moves up to the top of the cloud carried by convection curr curren ents ts,, whic which h can can ea easi sily ly lift lift the the ligh lightt posi positi tive vely ly char charge ged d particles. The effect produces a similar change at the earth's sur surface face due due to the char charge ge repul epulsi sion on,, of about bout the the sam same magnitude but opposite polarity.
The potential inside the cloud is usually of the order of several million volts and electric field may exceed 5 kV/m at ground level, which gives the creation of the upwards leaders rising from surface irregularities or metallic structures. (Fig.2 a). Electrical field is so strong that small discharges are produced from the cloud, known as step leaders. As these step leaders get closer to ground level, the upward leaders rise up to meet them. When the step leader and the upward leader meet, the circuit is completed creating a short circuit, the lightning strike, with discharges current from 10 to 200 kA (Fig. 2c). The energy carried by a lightning strike can easily reach 20 GW. The The most most comm common on ligh lightn tnin ing g stri strike kes s ar are e from from the the clou cloud d to ground (in 80% of cases), and are named negative discharges, discharges, but when the discharge is positive in the downward direction, the intensity is extremely high. 1.2. 1.2. Stat Statist istic ics s
The potential inside the cloud is usually of the order of several million volts and electric field may exceed 5 kV/m at ground level, which gives the creation of the upwards leaders rising from surface irregularities or metallic structures. (Fig.2 a). Electrical field is so strong that small discharges are produced from the cloud, known as step leaders. As these step leaders get closer to ground level, the upward leaders rise up to meet them. When the step leader and the upward leader meet, the circuit is completed creating a short circuit, the lightning strike, with discharges current from 10 to 200 kA (Fig. 2c). The energy carried by a lightning strike can easily reach 20 GW. The The most most comm common on ligh lightn tnin ing g stri strike kes s ar are e from from the the clou cloud d to ground (in 80% of cases), and are named negative discharges, discharges, but when the discharge is positive in the downward direction, the intensity is extremely high. 1.2. 1.2. Stat Statist istic ics s
Weather changes due to natural phenomena and to human activities are more and more important, affecting for example the the high higher er freq freque uenc ncy y and and the the inte intens nsit ity y of thun thunde ders rsto torm rms s worldwide. Known statistic information indicates that there are around 5,000 thunderstorms at any time around the world, with the associated threat to people and property, buildings, houses and and vari variou ous s indu indust stri rial al stru struct ctur ures es.. The The worl worldw dwid ide e aver averag age e discharge intensity of lightning strikes is reckoned to be 5 kA. Lightning density may vary in different parts of the world and periods of the year. In the Iberian Peninsula, about two million lightning strikes fall every year, killing people and animals. The faults and damages caused to industry by lightning every year can can be esti estima mate te in many many mill millio ions ns of euro euros. s. Of cour course se the the orog or ogrraphy aphy of ea each ch count ountry ry det deter erm mines ines the numb number er and and intensity intensity of thunderstorm thunderstorms s produced, produced, which can vary within an own country. Knowledge of the danger zones its an important info inform rmat atiion in orde rder to dete determ rmiine the the most ost app appro ropr priiate ate lightning protection system and its technical features. The Impacts of Lightning The effects of lightning may be classified as direct when is the result of an impact of a lightning strike or indirect when is due to the phenomenon of electromagnetic field generated during its discharge to the ground. (Fig. 1). Through a direct effects may have catastrophic consequences for people and animals, buildings, industrial structures and telecom antennas whilst the indirect effects tends to be more common, and causes huge financial losses.
Lightning strikes can affect directly (b) and indirectly (a). 1.3. Necessity Necessity of consider considering ing the the effects effects of direct direct and indirect lightning
The power of a direct strike to a facility is easy to understand as we visual visualise ise the potenti potential al result resultant ant damage damage.. Howeve However, r, a near strike can also cripple most facilities. •
The The mass massiv ive e amou amount nt of curr curren entt in a typi typica call ligh lightn tnin ing g discharge (30,000-50,000 A), has a large magnetic field that can couple into low voltage circuits destroying nearby communication, control and fire/security systems.
•
The voltage rise at the strike point can be several hund hundre reds ds of thou thousa sand nds s of volt volts s high higher er than than “rem “remot ote e earth”, causing current to flow in nearby circuits in an attempt to equalise voltages.
•
A strike to a distant power or phone line can cause a vol voltage age tra rans nsiient ent that that ente enters rs into nto your your faci facillity, ity, and and damaging equipment.
A strike some kilometres from a university raised the ground potential sufficiently that Ethernet circuits between buildings
were damaged. The copper circuits between building became a path for the equalisation current. The correct application of surge protection could have prevented the resulting damage. This is why an effective lightning protection system will include protection against the direct strike (i.e. an external lightning protection system), and protection against the indirect strike (i.e. an internal lightning protection system using Surge Protection).
2. LIGHTNING PROTECTION AND ITS WORKING
Lightning protection creates a preferred point for lightning to strike (avoiding strikes to sensitive rooftop equipment) using an air termination network, then conducts the energy to ground using down conductor(s) and injects the energy into a purpose designed earthing system. In some cases, existing structure materials can be used as part of the lightning protection system, such as using reinforcing steel as down conductors. The items are referred to as “natural components”. The use of existing structure items is most applicable to situations where the lightning protection is included in the initial design and construction. For buildings where lightning protection is retrofitted, it is often difficult to use “natural components”.
There are many possible designs for air termination networks, and final selection is based on efficiency of performance, ease of
installation/maintenance,
compatibility
cost,
visual
impact
with existing building materials. While
and the
traditional lightning rod is well known, horizontal conductors, handrails, parapet flashings and conductive roofing materials may also be used. Down conductors are selected to route the energy to ground and reduce the risk of side-flashing to nearby items. Routes are selected to reduce electromagnetic radiation and control risk of dangerous touch potentials being developed. The size and interconnection method of down conductors reduces the risk of heating and resultant structure fire during a lightning strike. For new concrete construction, the reinforcing steel within the building may be utilised. The earthing system is designed to inject the energy into ground and reduce the risk of voltage-ground-potential-rise (step and touch potentials). Various positioning and layout options are evaluated to select the best choice. Lightning protection systems are designed to: •
Reduce the presence of dangerous voltages (reduce step and touch potentials)
•
Reduce the risk of flash-over’s (reducing the risk of the building catching fire)
•
Reduce physical damage to buildings (stop holes being punctured in roofs, stop chucks of building materials being knocked out)
•
Reduce the risk of equipment damage
2.1. Protection zone
To aid in the design of the lightning and surge protection system, the concepts of “zones” is used. For example zones are classified based on: •
Is the area vulnerable to a direct strike?
•
Is the area exposed to the full or partial lightning current?
•
Is the area exposed to the full or partial electromagnetic field?
Zone
Lightning Flash
Current
Field
LPZ 0a
Yes
Full
Full
LPZ 0b
No
Partial
Full
LPZ 1
No
Limited
Partial
LPZ 2
No
Reduced
Reduced
To aid in the design of the lightning and surge protection system, the concepts of “zones” is used. For example zones are classified based on: •
Is the area vulnerable to a direct strike?
•
Is the area exposed to the full or partial lightning current?
•
Is the area exposed to the full or partial electromagnetic field?
Zone
Lightning Flash
Current
Field
LPZ 0a
Yes
Full
Full
LPZ 0b
No
Partial
Full
LPZ 1
No
Limited
Partial
LPZ 2 No Reduced Reduced By identifying the various zones around and within a structure, protection can be applied appropriately. For example, electrical services passing through a LPZ 0 zone will require surge protection where they enter into a LPZ 1 zone. Note that zones may not necessarily be physical boundaries of the structure 2.2. Isolated lightning protection system
Lightning protection systems may be isolated or non-isolated. Non-isolated systems electrically bond all conductive building materials together so they rise and fall at the same potential, eliminating potential differences and the risk of flash-over’s. This is the traditional lightning protection method. However, with modern facilities containing a large amount of electronic equipment, and more critically, rooftop equipment (air handling units, lift motors, TV aerials and communication equipment), non-isolated systems can be difficult and costly to implement. Isolated systems use special methods to capture the lightning strike and conduct this to ground without it contacting the structure. Isolated conductors are the main methods to achieve this. Isolated systems are ideal for: •
Highly flammable structures (grass/straw roofs)
•
Locations
with
a
high
concentration
equipment (communication towers)
of
electronic
•
Structures where the cost of bonding all metallic items would be prohibitive
Isolated systems are ideal to keep the dangerous lightning energy away from: •
Rooftop communication equipment
•
Solar cells and other electrical/electronic equipment
•
Explosion or gas hazard areas
2.3. Surge protection and its working
Surge protection devices are non-linear voltage dependent devices that transition from high impedance state to low impedance state to divert over voltages and over current safely
to ground. They are similar to a safety pressure value that stops dangerous pressures being built up in pressure vessels. The correct selection and installation of surge protection is essential for reliable performance. Unfortunately there are a number of people selling these products with little knowledge of
these
issues.
HV
Power
have
specialist
application
knowledge to guide you. It is important that: •
The right ratings are installed at the right locations
•
That electrical safety is maintained by having the correct backup over current protection
•
That devices are installed in such a manner to ease inspection and replacement
•
That the location and wiring to the SPD’s does not compromise the possible protection
•
That surge protection is properly coordinate
2.4. Coordinated protection
With surge protection designs, the normal approach to apply a large “lightning rated” surge protection device on the main service entrance. This stops energy entering the facility via the Z0/Z1 boundary. These are referred to as “Lightning Current Arrestors” (IEC 61643-11 Type 1). Secondary coordinated protection is then installed closer to the sensitive equipment to be protected. According to IEC 6164311 these SPD’s are Type II devices, or “Surge Arrestors”. You cannot rely on a Surge Protection Device (SPD) mounted in the main switchboard to protect equipment 10-100’s of metres away, especially when other loads in your facility may also be generating transient voltages. Having two SPD’s ensures the massive lightning current/voltage is suitably reduced so as not to damage sensitive equipment. The term "coordinated-
protection" is used as these two devices must be selected to work in a coordinated fashion. This first of this two-pronged approach diverts the bulk of the energy away from the point-of-entry to the facility, thus: •
Stopping
energy
radiating/coupling
from
entering
into
nearby
into
building low
and
voltage
data/communication circuits •
Stopping damage to electrical distribution boards (so power is not disrupted!)
•
Providing effective protection to robust downstream equipment such as heating and lights
The second of this two pronged approach, provides “fine” protection to the sensitive electronic equipment, thus: •
Protecting sensitive equipment to a suitable low voltage
•
Providing
backup if the point-of-entry protection is
damaged •
Protecting equipment from internally generated transients
3. LIGHTNING AND ITS CHARACTERISTICS 3.1. Likelihood of Lightning striking a building
This
cannot
be
precisely
determined,
but
some
rough
predictions can be made. The physics involved are too complex for this FAQ, but the following examples should give a few ideas. The variables involved are many: the local terrain, the shape and composition of the structure, nearby structures or trees,
and,
of
course,
the
overall
local
frequency
of
thunderstorms. Frequency of thunderstorms varies with the weather from year to year, but long-term averages can be used. Statistics are kept on the number of days that locations can expect to hear thunder. This is called the isokeraunic level. In addition to the isokeraunic level, the density of flashes to ground in a typical storm also can be calculated per square kilometer according to the local latitude. The other main factors are the height and area of the structure. As an example, calculations based on these factors show that an 80-foot tall building in Newport, Rhode Island, USA can expect to be struck by lightning approximately every 30 years, but a similar building in central Florida might expect a strike every six years. Put that Florida building in the shadow of a 1,000-foot skyscraper and the chance of it being struck is very low, if not zero. It is tempting to conclude that for many parts of the world, where lightning levels are low, the threat is negligible. But it is very important to remember that lightning need not strike a building directly to cause serious damage to any sensitive
electronic equipment that it might contain. It is common for lightning strikes several kilometers away to cause damaging electrical surges. And even in Newport, Rhode Island, where there are only about 20 thunderstorms a year, each square kilometer is struck an average of twice a year. This is enough to be of concern to facilities where damage can result in expensive downtime, the loss of important data or the potential to lose control over hazardous processes - not to mention the actual damage to costly electronic hardware. 3.2. lightning effect on a building
Direct and indirect effects are the two broad categories. Direct effects include the physical damage produced by lightning. Ignition of fires is a clear example caused by contact of the 20,000°C lightning
channel. Other
direct effects
include
shattering of wood, windows, masonry and other poorly conductive materials. Direct effects also include the burnout of electrical power and distribution equipment caused when lightning injects high currents and voltages into a power distribution line. A common example of this is the explosion of power distribution transformers. Lightning also causes a variety of indirect effects. These result from earth-voltage rises caused when the flash dumps thousands
of
amperes
into
the
earth
and
from
the
electromagnetic fields generated by the lightning stroke currents. These induce voltage and current surges in electric power and signal circuits, which may, in turn, burn out electrical equipment connected by these circuits. Solid-state
electronics are especially vulnerable to these surges unless properly protected. Of particular concern are facilities with several buildings or installations that are interconnected with above or below ground cables. These cables can experience significant induced transients. Power, telephone, data and even underground plumbing have the potential to transfer damaging lightning surges into a building. Even some fiber-optic cables can be susceptible to damage from lightning. Although the fiber-optic signal lines themselves are nonconductive, the cables are often constructed with a conductive metal sheath for strength purposes. Fiber-optic cable sheathes can attract lightning and its blast pressures may crush optical fibers. 3.3. Protection of buildings from direct effects
Since the time of Ben Franklin, the lightning rod, or air terminal, has been the front line of defense against lightning. Its basic concept is to provide a preferential terminal for lightning that would have otherwise hit a vulnerable part of the structure. An air terminal only will protect a portion of a building, so most structures will have several lightning terminals. The spacing and position of air terminals has been well understood for many years and the proper configuration and installation of air terminals is detailed in well-known standards,
such
as
NFPA
780
(National
Fire
Protection
Association). Basic direct-effects protection also includes a system of down conductors connecting the air terminals to the grounding system.
The configuration of the grounding system is very important and depends upon soil conditions, building construction and the presence of other underground conductors. Grounding systems can be created with driven ground rods, plates and possibly a counterpoise, which is a buried cable encircling the site. A counterpoise adds greatly to the protection from earth voltage rises that may injure people standing on the ground. The interconnection (bonding) of other metallic items in the building is important to prevent sparkover from a lightning conductor to other conductive items, such as water pipes, roof edgings, vent stacks or HVAC equipment, depending on their locations. 3.4. Protection of buildings protected from indirect effects
Lightning can cause damaging transient voltages and current surges in equipment through a direct strike to a wire, through earth voltage rise and through magnetic field and capacitive coupling. There are four engineering concepts that, when properly applied, can comprise a total lightning protection plan, whether for a single piece of equipment or a complex of buildings. These concepts are grounding, bonding, shielding and surge suppression. There is no magic bullet for lightning protection. Protection is achieved only through a careful investigation to identify all sensitive components and all possible paths for lightning
currents and voltages, followed by the design, specification, installation and maintenance of a protection system. Grounding and bonding improvements are made to provide additional paths for lightning currents to flow to earth, thereby minimizing
surges.
These
improvements
usually
involve
interconecting adjacent conductors, such as structural steel, conduits
and
grounding
ground
problems
conductors. include
Commonly
conduits,
metal
overlooked equipment
cabinets and individual components within computer rooms. Shielding of cables helps to reduce surges by providing a preferential path for lightning currents rather than the actual circuits. To be most effective, shielding must be completely continuous,
and
grounded
or
terminated
to
equipment
housings at both ends. In some cases, grounding, bonding and shielding provide a sufficient
reduction
in indirect effects.
However, critical
sensitive equipment, and any equipment interconnected by cables over long distances, requires the installation of surge suppressers. There are many types and many manufacturers of surge-suppression equipment. Care must be taken to select the most cost-effective device that will handle the currents and voltages expected from a severe strike. Surge suppressors should be installed where they readily can be inspected and replaced when damaged by a severe strike. In many cases, the most expensive surge suppressors turn out to be the least effective or appropriate for a particular application.
3.5. Protection of home and small business computers from lightning
By far the best way to protect your computer from lightning is to disconnect it from both the power line and telephone line at the approach of a thunderstorm. Commonly available surge strips do provide protection against some of the surges caused by lightning, specifically voltages induced between the positive and negative lines of the power supply. Surge strips do not always protect against voltages that arise between the power line and house, or system ground or the telephone lines. The larger concern, at least for any one capable of reading this FAQ, is the modem. Simply stated, your computer effectively forms a circuit between your local power company and your local telephone company. The interface between these two widely distributed
networks is your computer.
Lightning
commonly causes serious voltages to arise between circuits at different distances from the strike and/or referenced to earth ground at different locations. These voltages appear at the interfaces between these systems - your computer. It is a misconception to think that the lightning voltages are carried down the telephone lines to your computer. Rather, the voltages appear between the components of your computer. That is why a surge suppressor designed for a modem would be ineffective in most cases. This effect can be mitigated by providing a common ground reference for every device connected to your computer. In such a system, everything that is connected to the computer that has its own power or telephone connection is first connected to a device that
provides a single ground path. This device is based on the concept of an equipotential plane, commonly used for lightning protection of aircraft and other advanced systems. 3.6. Lightning in golf courses
Because public safety is the highest concern in any lightning protection program, the most important installation for a golf course is an early warning system. Early warning systems can include dedicated systems installed at the golf course or connections to realtime lightning data from a commercial network. In addition, strategically placed shelters should be designed and constructed to withstand all lightning effects. Please see our article on golf shelters available on this web site. Golf courses often have sophisticated irrigation systems with electronic controls. Because these systems have power and control cables distributed over many acres, they are highly susceptible to lightning-induced surges. Careful grounding and shielding and the installation of surge suppression devices can protect these systems. There are devices being marketed with claims that they actually reduce the likelihood of a lightning strike and others with claims to provide increased effectiveness as air terminals. What are the merits of these devices? Lightning Technologies, Inc. has no firsthand experience with these devices. Most such items are not available for purchase or installation other than directly through manufacturers and
their licensees, often making it difficult for independent evaluation. Moreover, LTI has had very good success with commonly available conventional parts and materials, and so has not found it necessary or useful to use expensive, unproven and sometimes controversial proprietary protection devices. To our knowledge, no independent studies have yielded any conclusive evidence of the effectiveness of many of these devices. Total lightning protection can be achieved with the proper planning and installation of conventional lightning-protection hardware and improvements to grounding, bonding, shielding, circuit design and surge suppression. Conventional inexpensive.
lightning-protection
hardware
is
relatively
4. LIGHTNING STROKE IMPACTS IN A BUILDING Lightning strokes can affect the electrical (and/or electronic) systems of a building in two ways:
by direct impact of the lightning stroke on the building (seeFig. 5 a );
by indirect impact of the lightning stroke on the building:
- A lightning stroke can fall on an overhead electric power line supplying a building (see Fig. 5 b ). The overcurrent
and
overvoltage
can
spread
several
kilometres from the point of impact. A
lightning stroke can fall near an electric power line
(see Fig. 5 c ). It is the electromagnetic radiation of the lightning
current
that
produces a high current and an overvoltage on the electric power supply network.
In the latter two cases, the hazardous currents and voltages are transmitted by the power supply network.
A
lightning stroke can fall near a building (see Fig. 5 d ).
The earth potential around the point of impact rises dangerously.
Fig. 5: Various types of lightning impact
In all cases, the consequences for electrical installations and loads can be dramatic. 4.1. Lightning falls on an unprotected building.
The lightning current flows to earth via the more or less conductive structures of the building with very destructive effects:
thermal effects: Very violent overheating of materials, causing fire,
mechanical effects: Structural deformation,
thermal flashover: Extremely dangerous phenomenon in the
presence
of
flammable
or
explosive
materials
(hydrocarbons, dust, etc.) The building and the installations inside the building are generally destroyed
4.2. Lightning falls near an overhead line
The
lightning
current
generates
overvoltages
through
electromagnetic induction in the distribution system. These over voltages are propagated along the line to the electrical equipment inside the buildings.
The
electrical
installations
inside
the
building
are
generally destroyed 4.3. Lightning falls near a building
The lightning stroke generates the same types of overvoltage as those described opposite. In addition, the lightning current rises back from the earth to the electrical installation, thus causing equipment breakdown.
5. VARIOUS MODES OF PROPAGATION 5.1. Common mode
Common-mode over voltages appear between live conductors and earth: phase-to-earth or neutral-to-earth (see Fig. 7 ). They are dangerous especially for appliances whose frame is connected to earth due to risks of dielectric breakdown.
Fig. 7: Common mode 5.2. Differential mode
Differential-mode
over
voltages
appear
between
live
conductors: phase-to-phase or phase-to-neutral (see Fig. 8 ). They are especially
dangerous
for
electronic
equipment,
hardware such as computer systems, etc.
sensitive
Fig. 8: Differential mode
6. PROCEDURE TO PREVENT RISKS OF LIGHTNING STRIKE The system for protecting a building against the effects of lightning must include:
protection of structures against direct lightning strokes;
protection of electrical installations against direct and indirect lightning strokes.
The basic principle for protection of an installation against the risk of lightning strikes is to prevent the disturbing energy from reaching sensitive equipment. To achieve this, it is necessary to:
capture the lightning current and channel it to earth via the most direct path (avoiding the vicinity of sensitive equipment);
This
perform equipotential bonding of the installation; equipotential
bonding
is
implemented
by
bonding
conductors, supplemented by Surge Protection Devices (SPDs) or spark gaps (e.g., antenna mast spark gap). minimize induced and indirect effects by installing SPDs and/or filters. Two protection systems are used to eliminate or limit overvoltages: they are known as the building protection system (for the outside of buildings) and the electrical installation protection system (for the inside of buildings).
7. BUILDING PROTECTION SYSTEM The role of the building protection system is to protect it against direct lightning strokes. The system consists of:
the capture device: the lightning protection system;
down-conductors designed to convey the lightning current to earth;
"crow's foot" earth leads connected together;
links between all metallic frames (equipotential bonding) and the earth leads.
When the lightning current flows in a conductor, if potential differences appear between it and the frames connected to earth that are located in the vicinity, the latter can cause destructive flashovers. 7.1. The 3 types of lightning protection system
Three types of building protection are used: 7.1.1. The simple lightning rod
The lightning rod is a metallic capture tip placed at the top of the building. It is earthed by one or more conductors (often copper strips) (see Fig. 12 ).
Fig. 12: Simple lightning rod 7.1.2. The lightning rod with taut wires
These wires are stretched above the structure to be protected. They are used to protect special structures: rocket launching areas, military applications and protection of high-voltage overhead lines (see Fig. 13 ).
Fig. 13: Taut wires 7.1.3. The lightning conductor with meshed cage (Faraday cage)
This
protection
conductors/tapes (see Fig.
involves symmetrically
placing all
numerous
around
the
down building. J14 ).
This type of lightning protection system is used for highly exposed buildings housing very sensitive installations such as computer rooms.
Fig. 14: Meshed cage (Faraday cage) 7.2. Consequences of building protection for the electrical
installation's equipment As a consequence, the building protection system does not protect the electrical installation: it is therefore compulsory to provide for an electrical installation protection system.
50% of the lightning current discharged by the building protection system rises back into the earthing networks of the electrical installation (see Fig. 15 ): the potential rise of the frames very frequently exceeds the insulation withstand capability of the conductors in the various networks (LV, telecommunications, video cable, etc.). Moreover, the flow of current
through
the
down-conductors
generates
overvoltages in the electrical installation.
Fig. 15: Direct lightning back current
induced
7.3. Lightning protection - Electrical installation protection
system The main objective of the electrical installation protection system is to limit overvoltages to values that are acceptable for the
equipment.
The electrical installation protection system consists of:
one
or
more
SPDs
depending
on
the
building
configuration;
the equipotential bonding: metallic mesh of exposed conductive parts.
7.3.1. Implementation
The procedure to protect the electrical and electronic systems of a building is as follows. 7.3.2. Search for information
Identify all sensitive loads and their location in the building.
Identify the electrical and electronic systems and their respective points of entry into the building.
Check whether a lightning protection system is present on the building or in the vicinity.
Become acquainted with the regulations applicable to the building's location.
Assess the risk of lightning strike according to the geographic location, type of power supply, lightning strike density, etc.
7.3.3. Solution implementation
Install bonding conductors on frames by a mesh.
Install a SPD in the LV incoming switchboard.
Install an additional SPD in each subdistribution board located in the vicinity of sensitive equipment (see Fig. 16 ).
8. CONCLUSIONS Thunderstorms and Lightning are climate related, highly localized
phenomena
in
nature
known
for
devastating
consequences. Many scientific experiments have culminated in inventions for lightning safety, yet the mystery behind lightning is still unresolved and lightning as a phenomena is not completely understood The technology of lightning protection have registered steady improvements but even with all the known precautions, complete safety is still beyond our grasp. Creating awareness among the general people could go a long way in mitigating lightning threats. The Asian countries like India, Sri Lanka, Bangladesh, Nepal and Bhutan have started Lightning Awareness Centres and one of their objectives is to spread awareness among the people. The High Powered
8. CONCLUSIONS Thunderstorms and Lightning are climate related, highly localized
phenomena
in
nature
known
for
devastating
consequences. Many scientific experiments have culminated in inventions for lightning safety, yet the mystery behind lightning is still unresolved and lightning as a phenomena is not completely understood The technology of lightning protection have registered steady improvements but even with all the known precautions, complete safety is still beyond our grasp. Creating awareness among the general people could go a long way in mitigating lightning threats. The Asian countries like India, Sri Lanka, Bangladesh, Nepal and Bhutan have started Lightning Awareness Centres and one of their objectives is to spread awareness among the people. The High Powered Committee
of
the
Government
of
India
on
Disaster
Management too has identified Thunderstorms and Lightning as natural hazards of great concern. The Bureau of Indian Standards purveys lightning protection guidance for structures and the builders are advised to adhere to the prescribed code. Research and Development programmes are being supported on lightning protection and many leading Indian institutes and Laboratories are working on lightning safety. The paper lays stress on spreading the culture of safety against lightning. It deals with the issues, Indian standards and methods of lightning protection, and introduces on going awareness programmes
and
research
and
lightning safety in the Indian context.
development
needs
for
Though lightning incidents are less, whenever they strike, they cause severe damages to life and properties. Casualties due to Lightning can be easily, efficiently and inexpensively avoided, and lightning safety can be achieved mainly by creating public awareness, technical
education
on Lightning
Protections,
educating people on lightning and surge protection. Stringent steps to ensure adherence of building standards and codes wherever necessary and promoting research and development on lightning protection are essential. There is a need to give lightning its due attention as a natural disaster and give it a priority in National Disaster Management Programmes.
