Lightning protection Protection of structures and open areas against lightning using early streamer emission air terminals.Part 2

hem) is the height difference between the air terminal tip and the horizontal plane


Rp(m) is the protection radius in the horizontal plane considered.

Radii of protection of the E.S.E. lightning conductors

Level of protection 11I(0 == 60 m)

2.2.4 Materials and dimensions

The E.S.E. lightning conductor partes) through which·lightning current flows should

be made of copper, copper alloy or stainless steel. The rod and the air terminal tip

should have a conductive cross-sectional area larger than 120 mm2•

2.2.5 Positioning E.S.E. lightning conductor

The ES.E. lightning conductor tip should be at le~st 2 metres higher than the

area that it protects, including antennae, cooling towers, roofs, tanks, etc.

The down-conductor is attached to the E.S.E. lightning conductor by a connecting

system located on the support rod. This connecting system consists of a suitable

mechanical device providing long=1astingeledrical contact.

If the external installation for a given structure comprises several E.S.E lightning

conductors, these are interconnected by a conductor complying with the data in

table 2.3.4, unless it has to be routed over a structural obstacle (cornice, parapet

wall) with a positive or negative level difference in excess of 1.50m (see figure –

When ES.E lightning conductors protect open areas such as playing fields, golf

courses, swimming pools, camping sites, etc.,they should be installed on specific

supports such as lightning poles, pylons, or any other nearby structures which

enable the E.S.E. lightning conductor to cover the area to be protected.

C 17-102 – July 1995 -18 – Elevation masts

The E.S.E. lightning conductor height may be increased by means of an elevation

masl If the E.S.E. lightning conductor is steadied by conductive guy lines, these

should be connected at the bottom attaching points to the down-conductors, by

means of conductors complying with table 2.3.4. Preferred installation points

The architectural features favourable to the E.S.E. lightning conductor installation

should be taken into account during the lightning protection system design.

Usually, these features are high structural points, such as :

– equipment rooms on flat roofs,

– gables,

– metal or masonry chimneys.


2.3.1 General principles

Down-conductors are designed to let the lightning current flow from the airtermination

systems to the earth termination system. .The down-conductors should

be installed outside of the structure, except in the cases mentioned in

2.3.2 Number of down-conductors

Each E.S.E.· lightning conductor should be connected to the earth termination

system by at least one down-conductor. Two or more down-conductors are

required when :

-·the horizontal projection of the conductor is larger than its vertical projection (see

figure 2.3.2) ..

– ElPls are installed on structures higher than 28m.

The down-conductors should be installed on two different main walls.


-19 – C 17-102 -July 1995

A <28m and A > B : 1 down-conductor




A> 28m or A<B : 2 down-conductors

A : Vertical projection of down conductor

B : Horizontal projection of down conductor

Figure 2.3.2 – Number of down-conductors


The down-conductor should be installed in such a way that its path is as direct as

possible. The down-conductor routing should take into account the earth

termination location (see 2.5.2). It should be as straight as possible along the

shortest path without sharp bends or upward sections. The bend radii should not

be less than 20 cm (see figure 2.3.3). For the diverting of down-conductors, bends

formed edgewise should preferably be used.

The down-conductors should not be routed along or across electrical conduits.

However, when electrical conduit crossing is unavoidable, the electrical conduit

should be placed inside a metal screen which extends 1m beyond the point of

crossing. The screen should be connected to the down-conductor.

Routing round parapet walls or cornices should be avoided. Provisions should be

made to ensure that down-conductor paths are as direct as possible. However, a

maximum height increase of 40cm is permissible for passing over a parapet wall

with a slope of 45Q or less(see figure 2.3.3 e).

C 17-102 -July 1995 – 20-


[ = length of the loop in metres,

d = width of the loop in metres.

No risk of dielectric breakdown if the requirement d > [/20 is met

Figure 2.3.3. LPS down-conductor bend shapes

The down-conductors should be attached on the basis of three fixings per metre.

The flXings should be suitable for the supports and their installation should not

alter the roof water-tightness. The fixings should allow for possible thermal

expansion of the conductors.

– 21 – C 17-102 -July 1995

All the conductors should be connected together by means or clamps ef the same

material. or by solid rivets, soldering or brazing. Drilling through down-conductors

should be avoided wherever possible.

Down-conductors should be protected against the risk of impact by installing

sleeves up to a height of 2m above ground level. Internal routing

When external routing is impracticable. the down-conductor may be routed inside

a specific service duct running along the full height or part of the height of the


Insulating non-flammable internal ducts may be used when their internal crosssectional

area is 2000 mm2 or more. The proximity requirements stated in

chapters 2 and 3 should be complied with in all cases.

The down-conductor system effectiveness may be reduced by internal routing.

The project manager must be aware of the reduced lightning protection system

effectiveness, inspection and maintenance difficulties, and the risks resulting from

the entry of voltage surges into structures. External cladding

When the outside of a building or structure has a metal cladding or stone or glass

curtain-walls, or in the case of a fixed cladding item, the dov:n-conductor may be

attacr.ed behind the cladding to the concrete wall or the load-bearing structure.

In such a case, the conductive cladding componen~s and the supporting structure

lTlust be bonded to the down-conductor at the top and bottom ends.

2.3.4 Materials and dimensions

Down-conductors’ consist of strips, braided cables, or round sections. Their

minimum cross-sectional area of 50mm2 is defined in table 2.3.4.


Minimum dimeInsions Remarks

SRtreipco: m3m0exn2dmemd for its

Rgoooudndcosnedcutioctniv: ity8mamnddia.

Braided cable: 30×3.5mm

SRtericpo:m3m0~xn2dmemd in certain


RoUnd 8mm dia.


STotripb:e 3u0sxe3dmomn aluminium

Round section: 10mm dia.


Table 2.3.4

C 17-102 – July i!!!?5 – 22-

The use of insulated coaxial cables as down-conductors is not permitted. The use

of insulating sheaths or coatings around down-conductors is not permitted except

for the cases described in 5.2.


(1) Tin-plated copper is recommended in view of its physical, mechanical and

electrical properties (conductivity, malleability, corrosion resistance, etc.).

(2) As the lightning current has an impulse characteristic, the flat conductor is

preferred to the round conductor since its outside surface area is larger for a

given cross-sectional area.

2.3.5 Test clamp/Disconnect terminal (or test terminal)

Each down-conductor should be provided with a testdamp used to disconnect the

earth termination system for measuring it. The test clamp should .bear the term

“lightning conductor” and the symbol @.

Test clamps are usually installed on the down-conductors at height of about 2 m

above ground level. When lightning protection systems have metal walls or are not

provided with specific down-conductors, test clamps are inserted in between each

earthing system and the metal building item to which the earth termination system

is connected; the test clamps are installed inside inspection chambers which bear

the symbol @. .

2.3.6 Lightning flash counter

When a lightning flash~ceunter is~provided, it should be installed on the most direct

down-conduclor. above the test· clamp and, in any case, at height of about 2m

above ground level.

2.3.7 Natural com~onents

Some conductive structural components may be used in place of an entire downconductor

or part thereof, or supplement the down-conductor. Natural components which can be used in place of the entire downconductor

or part thereof

Generally, external interconnected steel frames (metal structures) can be used as

down-conductors in so far as they are conductive and their resistance is 0.01 nor


In such a case, the upper end of E.S.E. lightning conductors is connected directly”

to the metal frame whose lower end is to be connected to the earth termination


The use of a natural down-conductor should meet the equipotential bonding

requirements stated in chapter 3.

– 23- C 17-102-July 1995

Note : As natural components may be modified or removed without the fact that

they belong to a lightning protection system being taken into account, specific

conductors should be preferred. Natural components which can be used to supplement down-conductor(s)

The following items can be used to supplement the lightning protection system and

be connected to it :

(a) interconnected steel frames providing electrical continuity

– internal metal structures, concrete reinforcements and metal structures sunk

into walls, subject to specific connection terminals being provided for this

purpose in the upper section and lower section (at least in three points at

each level);

– external metal structures which do not run over the entire structure height.

Note : When prestressed concrete is used, special attention should be paid to .

the risk of mechanical effects due to the lightning current flowing through the

lightning protection system.

(b) metal sheets covering the area to be protected, provided that ~

– long-lasting electrical continuity is provided between all the parts;

– metal plates are not coated with insulating material.

Note : A light coat of protective paint, a 1mm thick asphalt film or a O.5mm

thick PVC film is not considered as an insulation.

(c) metal pipes and tanks if made of material 2mm thick or more.




When lightning current flows through a conductor, differences of potential appear

between this conductor and nearby earthed metal parts. Dangerous sparks may

be produced across the ends of the resulting open loop.

Depending on the distance between the ends of the open loop (down-conductor(s)

and earthed metal part), equipotential bonding· mayor may not be achieved. The

minimum distance at which no dangerous sparks can be produced is known as the

safety distance s and depends on the selected protection level, the number of

down-conductors, the material between the loop ends, and the distance from the

metal part considered to earth connection point.

C.~7-102 – July 1995 – 24-

It is often difficult to provide for insulation during the installation of the lightning

protection system (through lack of information needed to take a decision), or to

provide for long-term insulation (structural changes, work, etc.). Equipotential

bonding is therefore frequently preferred.

However, equipotential bonding is not provided in some cases (flammable or

explosive piping). The down-conductors are then routed further away than the

safety distance s (see 3.2.1 (c».

3.1.1 Equipotentialbonding

The equipotential bonding should be provided wherever possible at the closest

point by an equipotential conductor, a lightning arrester or a spark gap, between

the down-conductor or: the E.S.E. lightning conductor draining the lightning current

and the component to be put at the same potential and located on the structure. in

the structure walls or inside the structure. .

3.1.2 Safetydistance

The safety distance is the minimum distance at which no dangerous spark is

produced between a down-conductor draining the lightning current and a nearby

earthed conductive mass (see figure 4.5).

The insulation with respect to dangerous sparks is achieved when the distance d

between the lightning protection system and the conductive item considered is

more than ds.


Safety distance: S(m) = n. km I(m)


(Equation 3)

– n is the number of down-conductors for each E.S.E. lightning conductor before

the contact. point considered :

n = 1 for one. down-conductor,

n = 0.6 for two down-conductors.

n = 0.4 for three or more down-conductors.

– ki is a factor related to the selected protection level:

kj = O.1for protection level I,

kj = 0.075 fo~ protection level 11,

kj = 0.05 for protection level Ill.

. – km is a factor related to the material used between the two loop ends:

km = 1 for air, .

km = 0.5 for asolid material which is not a metal.

– I (in meters) is the length along the down-conductor(s) from the point where the

proximity is to be considered to the earthing system of the metal part or the

nearest equipotential bonding point.

– 25- C 17-102 -July 1995


(1) When the nearby conductive part is not electrically earthed, it is not necessary

to provide an equipotential bonding.

(2) When the LPS is connected to reinforced concrete structures with

interconnected reinforcing steel and in case of steel frame structures or of

structure~ equivalent screening performance, proximity requirements are

usually met.


In most cases. a connection using an equipotential conductor is possible. If it is

not possible or authorised by the competent authorities, the connection must be

made using a surge protective device.

3.2.1 Equipotential bonding using an equipotential conductor

Equipotential bonding shoul~ be provided at the following locations:

(a) Above the ground and underground.

All the structur~ earth terminals should be interconnected as· provided for in

paragraphs 4.4 and 4.5.

(b) Whenever the proximity requirements are not met: when d<s.

In such a case, the acceptable equipotential conductors should be of the.

same type as those used to make down-conductors (table 2.3.4). They should

be kept as short as possible.

In the event of a lightning protection system separated from the structure to

be protected, the equipotential bonding should be made at ground level only.

(c) In the case of gas service pipes located downstream of the insulating sleeve,


3.2.2 Equipotential bonding using a surge protective device

An antenna or a small post supporting electrical lines should be bonded at the

nearest to the down-conductor, via a antenna-mast spark-gap type surge

protective device.

If pipe lines (water, gas, etc.) with insulated parts are (aid within the space

considered, such insulated parts should be by-passed by the surge protective



The guidelines stated in paragraphs 3.2.1 (a) and (b) are still applicable in so far as

connecting terminals have been provided for this purpose in the relevant batches.

. Special. attention sho~ld be paid to wa·ter-tightness problems.

C 17-102 -July 1995 . – 26 –

Note: For existing structures, the competent authorities should be contacted.



Equipotential conductors should be used to connect internal metal parts to an

equipotential bonding bar made and laid out in such a way as to allow easy

disconnection for inspection purposes. The minimum cross-sectional area of such

conductors should be 16 mm2 when they are made of copper or aluminium, or 50

mm2 when they are made of steel. The equipotential bonding bar should be

connected to a point as close to the structure earthing circuit as possible. For large

structures, several equipotential bonding bars may be installed provided that they

are interconnected. Each equipotential bonding bar should be made of copper or

the same material as the equipotential conductor anq its minimum cross-sectional

area should be 75 mm2. .•

For electrical or telecommunication systems, using screened conductors, or

conductors installed inside a metal conduit, earthing the screens or metal conduits

usually provides suffiCient protection.

If not, the active conductors should be bonded to the lightning protection system

via surge protective devices.



One earth termination system is provided for each down-conductor.

To allow for the impulse characteristic of the lightning current and to enhance

current draining to earth, while minimising the risk of dangerous voltage surges

within the protected volume, it· is also important to pay attention to the earth

termination system shape and dimensions and also to the earth termination

resistance value.

Earth termination systems should meet the following requirements:

– the resistance value measured using a conventional equipment should be

10 ohms or less. This resistance should be measured on the earthing termination

insulated from any other conductive component.

– the wave impedance or inductance value should low as possible in order to

minimise the back-electromotive force which is added to the ohmic potential rise

occurring during the lightning discharge. For this purpose, earth termination

systems having a single excessively long horizontal or vertical component should

not be used.

The use of a single vertical termination system deeply buried to reach a humid

layer of soil is thus not aqvantageous unless the surface resistivity is particularly

high. .

·27· C 17-102 -July 1995

It should however be noted that such drilled earth termination systems have a high

wave impedance when the. depth exceeds 20 metres. This calls for the use of a

greater number of horizontal conductors or vertical stakes which must always be

perfectly interconnected from an electrical standpoint. Similarly, copper conductors

should be preferred to steel conductors whose cross-sectional area required to

achieve equivalent conductivity makes their use impracticable.

Earth termination systems should be made and laid out as stated above and in

section 544 of standard NF C 15-100.

Unless there is a real impossibility, earth termination systems should always be

directed outward from the buildings.


The earth termination system dimensions depend on the soil resistivity in which

the earth termination systems are installed. The resistivity may vary to a

considerable extent depending on the soil material (clay, marf, sand, rock, etc.).

The resistivity can be assessed from the table below, or measured using a suitable

method with an earth ohmmeter.

Once the resistivity is known, the length of an termination system can be

determined using the following simplified equations: .

Linear horizontal termination system Vertical termination system

L = 2p1R (Equation 4) L = p/R (Equation 5)

L is the termination system length (in m)

p is the soil resistivity (in n.m) .

R is ~hedesired resistance value (:s10 n)

C 17-102 -July 1995 – 28-

Soil Resistivity in n.m

a few units up to 30



















Table 4.2

For each down-conductor, the earth termination systems should at least consist of:

(a) conductors of the same material and cross-sectional area as the downconductors,

except for aluminium, arranged in crow’s foot fashion and buried

at a minimum depth of 50 cm.

Example: three7-8-metre long conductors, buried horizontally at a minimum

depth of 50 cm; or

b) a set of several vertical stakes totalling a minimum length of 6 metres.

– arranged in line or as a triangle and separated from each other by a distance

equal to at least the buried length;

– interconnected ‘”by a conductor which is identical to or has characteristics

compatible with the down-conductor, and buried in a trench at a minimum

depth of 50 cm.

Note : The recommended lay-out is the triangle.

– 29- C 17-102 – July 1995

Disconnectable I





D : Down-conductor

B : Building foundation loop earth

P : Lightning earth termination system


Figure 4.2 – Typical earth termination system diagrams


When the high soil resistivity makes it impossible to achieve an earth termination

system resistance lower than 10 ohms using the above standard protective

measures. the following additional measures may be used :

– add na..tu•.ral materia.l with a lower resistivity around the earth conductors;

– add earth rods to the crow’s feet or to the stakes already installed;

– augment the number of earth termination systems and interconnect them;

– apply a treatment which reduces the impedance and features high current

draining capacity;

– ~hen all the above measures are adopted and a resistance value of less than 10

ohms cannot be obtained, it can be considered that the earth termination system

provides acceptable lightning current draining when it consists of a buried

termination system at least 100m long. assuming that each vertical or horizontal

element is not more than 20 m long.


When the building or the protected volume has a foundation earth termination

system for the electrical system in compliance with article 542.2 of standard NF C

15-100, the LPS earth termination systems should be connected to it by a

standard sized conductor (see tables 2.3.4 and 4.6).-

For new installations, this measure should be taken into account as from the

design stage, and the interconnection to the foundation earth circuit should. be

made right in front of each down-conductor by a device which can be

disconnected and located in front of an inspection chamber bearing the symbol

C 17-102 -July-1995 – 30-

For existing buildings and installations, ~he connections should be made preferably

on the buried parts and it should be possible to disconnect for inspection


When the interconnection is made inside a building, the interconnecting conductor

should be routed in such a way that no currents are induced in nearby cables or


When several separate structures are included in the protected volume, the E.S.E.

lightning conductor earth termination system should be connected to the buried

equipotential earth network interconnecting all the structures.


The LPS earth termination components should be at minimum distances away

from any buried metal pipe or electrical conduit.

The minimum distances are indicated in table 4.5 hereunder:

Buried services Minimum distances

resistivity ~ 500 n.m

Soil resistivity> 500 n.m

0.5 0.5

Electrical conduit LV


20 10

MLVelami apinipsessufpoprlygas

5 2

Table 4.5

These distances are’. applicable only with conduits which are not electrically

connected to the main. equipotentiallink of the building.

Note: In the case of non metal conduits, compliance with a minimum distance is

not required.


The materials and the’ minimum dimensions for the earth termination systems are

given in the table below.

. – 31 – C 17·102 – July 1995

Earth termination systems


for the good


Grid made of wire with a min.


Rod: 15mm dia., 1m 19

18/10 – 304 stainless steel

RSetrcipo:m3m0exn2dmemd in certain

Round section: 10mm Rod: 15mm dia.

SRterispe:rv3e0dx3fo.5r mprmovisional

sRhoournt-dtesrmectiinosnt:all1a0timonms dia.

Rod :”19mm dia., 1m 19

Table 4.6

Note: (1) TIn-plated copper is recommended in view of its physical, mechanical

and electrical properties (conductivity, malleability, corrosion resistance. etc.).



The corrosion of metals depends on the type of metal used and on the

characteristics of the metal environment. Factors such as fungus, soluble salts

(electrolytes), degree of ventilation, electrolyte temperature and changes make the

conditions highly complicated. “

The contact of dissimilar metals associated with electrolysis phenomena due to

the environmentincreases corrosion in more anodic or active metal and decreases

corrosion in more cathodic or inert metal. Corrosion in more cathodic metal should

be prevented. The electrolyte for this reaction may be” a humid soil, or

condensation retained in cracks.


In order to reduce corrosion, it is necessary to :

– avoid the use of unsuitable metals in an aggressive environment,

– avoid contacts between dissimilar metals with different galvanic couples,

– use conductors of appropriate gauges and corrosion-resisting fasteners,

C 17-102 -July 1995 ·32 –

– provide protective coatings In critical cases as appropriate to the external


To meet the above requirements. the following precautions are given as typical


– the minimum, thickness or diameter or a conductive item should comply with the

provisions of this standard.

– aluminium conductors should not be buried or embedded directly in concrete.

unless they are provided with a suitable long-lasting sheath,

– copper/aluminium joints should be avoided wherever possible. If unavoidable,

joints should be made using suitable two-metal connections.

– copper is usually suitable for earthing, except under certain acid conditions,

when exposed to oxygen or sulphate,

– when there are sulphuric or ammoniacal fumes, a coating may be used on the


Note : The use of insulating material of thickness less or equal to 0.5 mm is


– conductor fasteners should be mace of stainless steel er a suitable synthetic

material under corrosive environmental conditions.



An antenna on the roof of a building increases the lightning stroke probability and

is the first vulnerable item likely to receive the lightning discharge.

When this is an individual or collective radiobroadcasting receiver antenna,

complying with the standard *, the antenna support mast should be connected

through a surge protective device or a spark gap to the dcwn-conduc:ors of the

installation by a standard conductor unless the antenna is outside the protected

area or on another roof.

A common support mast can be used under the following conditions:

– the common support mast consists or adequately slrong tubes which do not need

guy lines,

– the E.S.E. lightning conductor is attached to the tip of the mast.

Materiel electronique et de telecommunications – Antennes individuelJes ou collectives de

radiodiffusion sonore ou visuelle : Regles (StandarcrNF C 90-120 • October 1983, published by Union

Technique de I’electricite).

– 33 – . C 17-102 . July 1995

– the E.S.E. lightning conductor tip is at least 2 m above the nearest antenna,

– the down-conductor is attached by a clamp which is fastened directly onto the

md. –

– the antenna coaxial cable is routed inside the mast antenna.

In the case of a lattice mast. it is preferable to route the coaxial cable through a

metal tube.


In this case, the E.S.E. lightning conductor should preferably be installed on the

chimney if it exists. The down-eonductor should be an 8mm diameter annealedcopper

round conductor which should be routed along the roof ridge on stand-off

insulators with a clear space of 20-25cm and down oil thatch gutters.


As factory chimneys are very tall and smoke and hot gasses ionise the air, they

are highly prone to being struck by lightning.

The upper part of the chimney should be provided with a E.S.E. lightning

conductor, preferably using materials suited to the corrosive atmosphere and

exhaust temperature, and located on the prevailing wind side.

For chimney height 40 metres high or more. two down-conductors mInimum

should be installed diametrically opposed’ with one being located on the prevailing

wind side. These down-conductors should be interconnected at the upper end and

at the base of the chimney by an harizontal conductor. Ea<;hdown-conductor

should be provided with an earth termination system.

The external and internal metal items should be connected to the nearest downconductor

under the same conditions as those stated in Chapter 3.


In compliance with the current regulations, tanks containing flammable fluids

should be earthed but such an earth connection does not provide adequate

protection against atmospheric discharges. A thorough additional survey is

therefore necessary.

E.S.E. lightning conductors should be erected on masts, poles, pylons, or any

other structure outside the safety area so as to be above the installations to be

protected. Their location should take the protection radii into account in

accordance with this.standard.

Earth termination systems should be oriented away from the storage installations.

The E.S.E. lightning conductor and protected installation earth termination

systems should be equipotential.

C 17-102 – July 1995 – 34-

Note : The Ministerial Decree dated January 28. 1993 concerning the lightning

protection of certain classified installations makes the installation of lightning

stroke counters compulsory.


Steeples, towers, minarets and belfries are prone to being struck by lightning

because of their prominence.

The main prominence(s) should be protected with E.S.E. lightning conductors

connected to the ground by a direct down-conductor routed along the main tower.

A second down-conductor following the nave ridge should be provided when one

or more of the following conditions is met:

– the total steeple height exceeds 40 metres,

– because of its length, the nave extends outside the E.S.E. lightning conductor

protection area.

In this case, the second down-conductor should originate from the summit of the

main tower.

When a church is fitted with two down-conductors, and the end of the nave is fitted

with a non-metallic cross or statue, the cross or statue will be provided with a air


Both LPS earth termination systems and the electric earth are preferably

interconnected by an earth conductor.

Some religious buildings have electric bells. The electrical power supply is

protected against voltage surges by lightning arresters complying with article 3.


H~40m H>40m

Figure 6.5 – Religious building

– 35- C 17-102 -July 1995


Mountain restaurants, refuges, cableway statiQns are particularly prone to being

struck by lightning. The E.S.·E.lightning conductors may be installed in compliance

with the provisions of this standard, paying. special attention to the equipotential

bonding and earth termination systems.


Play fields, camping and caravan sites, swimming pools, racecourses, motor

racing circuits, amusement parks, etc.

The E.S.E. lightning conductors are installed on flagpoles, floodlight masts, pylons,

or any other existing structure. Their number and location depend on the type and

area of the surfaces to be protected in complian~e with the provisions of this



Certain isolated trees are potentially prone to lightning strikes because of their

height and shape.

Wherever the risk of lightning strike involves hazard to close structures (e.g.,

nearby building), or historical or aesthetic interests ~re involved, the tree may be

usefully protected against lightning by installing an E.S.E. lightning conductor at its

t~p in compliance with the provisions of this standard.

The easiest way to install the down-conductor which does not hinder the tree’s

growth and. damages it as little as possible is to {Jse a conductor in the form of a

flexible braided cable secured by suitabie fasteners taking the most direct path

possible along the tree trunk.


LPS maintenance i~ essential since a number of components may lose their

effectiveness over time due to corrosion, weather, mechanical impacts, and

lightning. The mechanical and electrical characteristics of an LPS should be

maintained throughout the LPS life in order to meet the standard requirements.

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