Lightning protection Protection of structures and open areas against lightning using early streamer emission air terminals.Part 3

7.1 INITIAL INSPECTION .

Once the E.S.E. lightning conductor installation is completed, it should be

inspected to make sure that it complies with the provisions of this standard.

The purpose of this inspection is to make sure that:

– the E.S.E. lightning conductor is 2 metres or more above the entire protected

area,

– the materials and the gauges used for the down-conductors are suitable,

C 17-102 -July 1S95 – 36·

– the down-conductors are routed, focated and electrically bonded as required,

– all the installation components are firmly secured:

– the safety distance(s) is(are) respected and/or equipotential bondings are

provided,

– the earth termination system resistance values are correct,

– the earth termination systems are interconnected.

This inspection should be performed visually under the conditions stated in part 6

of standard NF C 15-100.

However, where a conductor is entirely or totally hic;1den,its electrical continuity

should be tested. Such a test should conform to part 6 of standard NF C 15-100.

7.2 SCHEDULEDINSPECTION

The inspection frequency is determined by the protection level. The following

inspection intervals are recommended:

INntoernmsaiflieidnteinrfvearlval

2 YEA1RYSEAR

3 YE2ARYSEARS

YE2AYRESARS

Note: The intensified interval is recommended in a corrosive atmosphere.

An LPS should also be inspected whenever the protected structure is modified,

repaired or when the structure has been struck by lightning.

Note : Lightning flashes can be.recorded by a lightning flash counter installed on

one of the down-conductors.

7.2.1 Inspection procedure

A visual inspection should be performed to make sure that:

– no extension or modification of the protected structure calls for the installation of

additional lightning protective measures,

– the electrical continuity of visible conductors is correct, .

– all component fasteners and mechanical protectors are in good condition,

– no parts have been weakened by corrosion,

– the safety distance is respected and there are enough equipotential bondings

and their condition is correct.

·37 – C 17-102· July 1995

Measurements should be taken to verify :

– the electrical continuity of hidden conductors,

– the earth termination system resistance values (any variation should be

analysed).

7.2.2 Inspection report

Each scheduled inspection should form the subject of a detailed report containing

all the findings of the inspection and the corrective measures to be taken.

7.3 MAINTENANCE

Any faults found in the LPS during a scheduled inspection should be corrected as

soon as possible in order to maintain its optimal effectiveness.

C 17·102 -July 1935. -38 –

..—…..-.

Ai

A 1.1

«,

«~ ‘

…… :~:- …

APPENDIX A

(Normative)

PROTECTION MODEL

ATIACHMENT PROCESS DESCRIPTION

Striking point determination

The formation or arrival of a stormy cloud .creates an electrical field (ambient)

between the cloud and the ground. This electrical field may exceed 5 kV/m on the

ground, thereby initiating corona discharges from ground reliefs or metal parts.

The lightning stroke begins with the formation of a downward leader within the

stormy cloud which propagates in steps towards the ground. The downward leader

conveys electric charges which causes the ground field to»build up.

An upward leader develops from a structure or an object linked to the ground. The

upward leader propi;lgates until it joins the downward leader and the lightning

current flows through the resulting channel. Other upward leaders can be emitted

~y several ground structures. The first one which joins the’ downward leader

determines the lightning striking point (Fig. A1).

Figure Ai

Note : This description only concerns the negative downward lightning stroke,

which is the only application case of the electro-geometrical model. This type of

lightning stroke is by far the most frequent.

A 1.2 Leader propagation velocity

Recent experimental data obtained from the nature shows that the average

velocities of the upward and downward lead~rs are comparable during the

attachment phase and the velocity ratio vuplvdown is close to 1

-39 – C 17-102-July 1995

Assuming that v = vup = vdown = 1 m/lJs (average measured leader velocities),

where:

vup is the upward leader velocity,

vdown is the downward leader velocity,

v is the common velocity.

A 2 ADVANTAGE OF AN E.S.E. LIGHTNING CONDUCTOR IN TERMS OF

PROTECTION

A 2.1 Triggering advance

An E.S.E. lightning conductor is built to reduce the average statistical time related

to the upward leader initiation. An E.S.E. lightning conductor features an triggering

advance as compared with a simple rod lightning conductor installed under the

same conditions. This gain in time is assessed in a l:Iigh-voltage test laboratory as

recommended in paragraph 2.2.2.1 and Appendix C to this standard.

A 2.2 Gain in length of the upward leader

The gain in upward leader length L\L is given by 6L(m) = V(m/lJs) .6T(lJs).

The protected volume is determined from the protection model described above

on the basis of the electra-geometrical model.

A3

MODEL OF PROTECTION

Protection radius of a S.R. lightning conductor

In the caze of a simple rod, according to the electra-geometrical model, the

lightning striking point is determined by the ground object which is the first one to

be located at a distance D from the downward leader even though this object is

the flat ground itself. The distance 0 between the strike point and the upward and

downward leader joining point is known as the «striking distance» : this is also the

development length of the upward leader.

Therefore, it appears as if a fictitious sphere of radius 0 was centred on and

moving rigidly with the downward 1eader head.

Considering a simple rod of height «h» relative to the reference surface (building

roof, ground, etc.), there are three possibilities (see figure A 2) :

Figure A 2 • Fictitious sphere method

– if the sphere comes into contact with the vertical rod (A’) only, the vertical rod will

be the strike point,

– if the sphere comes into contact with the reference surface and not with the

vertical rod, the strike point will be on the ground at S only,

– if the sphere comes into contact with both the simple rod and the reference

surface at the same time, there are two possible strike points: A’ and C’, but the

lightning discharge will never strike the hatched area (see figure A 3).

h

Figure A 3

The striking distance 0 is generally given by the ‘following equation:

D(m) = 10.1213,where

I is the peak current ?f the first return stroke in kiloAmperes (kA).

A 3.2 Protection radius of an E.S.E. lightning conductor

In the case of an E.S.E. lightning conductor of triggering advance ~T, and with jL

=: v.,;lT. the possible strike points are A and C (Figure A 4) with a protection radius

Rp. such that: .

·41 – C 17-102 – July 1995

Rp = J h (20 – h) + tlL (20 +llL)

where:

o is the striking distance

I1L is the upward leader length gain defined by ~L = v.~T

h is the E.S.E. lightning conductor tip height above the surface to be protected.

Rp is the E.S.E. lightning conductor protection radius

11T is the triggering advance ofthe E.S.E. lightning conductor. ,

Figure A4

C 17-102 -July 1995 . – 42 –

APPENDIX B

(Normative)

LIGHTNING RISK ASSESSMENT GUIDE AND

SELECTION OF PROTECTION LEVEL FOR AN ELPI

B 1 GENERAL

The lightning risk assessment guide is intended to assist the design manager in

the analysis of all the criteria used to assess the risk of damage due to lightning

and to determine the need for protection and the required protection level. Only

the damage caused by a direct lightning stroke on the structure to be protected

and the lightning current flow through the LPS is covered. .

In many cases, the need for protection is obvious. EXamples are:

– large crowd,

– service continuity, –

– very high lightning stroke frequency,

– tall or isolated structures,

– building containing explosive or flammable materials, or irreplaceable cultural

heritage.

Some typical consequences of a lightning stroke on several types of common

structures are listed in table B1 for information.

Structure classification Structure tLyipgehtning consequences

equipmeonfitnsetalellcaatntriidocnaslP,erfofirraetion

to the lightning

Risk of fire and dangerous sparks.

tRRhieisskkIQocSofSnsostefepqvuevenontlitltaagtitoeon. p·ocwoenrtroflaialunrde fo:ocdattdleistrdibyuintigona. s a result of

ThReisaktreo,f spcahnoicol,and fire alarm failure resulting in delayed fire

hypermfigahrktientgs., sports

Bank, insurance

ab~ve plus problems related to loss of information

and computers malfunction.

care

.

Same as above plus problems related to patients in intensive

care units and evacuation of handicapped persons.

Additional effects depending on the factory contents, ranging

lforosms. minor damage to unacceptable damage and production

Irreplaceable losses in cultural heritage.

-43 – C 17-102 – July 1995

Table 81

Note : Sensitive electronic equipment may be installed in any type of structures

and can be. $asily damaged by voltage surges due to lightning.

A riskasses’Sment method is proposed in this guide, it takes into account the

lightning risk and the following factors:

.. ,

,1. Building environmer;1t,’: .

.’····2. Type of construction’, :….

. .’..- 3. Structure contents· •… ··

‘ ..’ 4. Structure occupancy,

, ..·5~ Ligjltning st~oke consequences.

The building’ location in the environment, and the euilding height are taken into

consideration for the computation of the’exposure risk ..

In some cases ho~ever, certain criteria specific to ~ ~iven structure cannot be

assessed and may prevail over any other consid.eratjon. Protective measures can

then be applied which are more .stringent than’th.ose resulting from the application

of the guide. ….’: .’ .’

The selection of the suitable protection level for the ELPI to be installed is based

on the expected direct lightning stroke frequency on the structure or the area to

be protected and on the accepted yearly lightning stroke frequency Nc.

B 2 Determination of Nd and Nc

8 2.1 Lightningflash densityNg

The lightning flash density is expressed as the yearly number of lightning flashes

per km2 and can be determined by :

– ~ theslrokedensitymap Na i1 FJgUre 84. rnthiscase,Ng= Na/2.2

– oonsuIlinga [ghtningkx:ationnebNork, .

-l.ISirg thelocalisoI<eraunK:: level~ : Ng l1BX =0.04 ~ 125 == ~/10

The value Ng max takes into account the maximum lightning density and the

Note: The map of figure 84 shows the stroke density. The constant 2.2 is the

average ratio of the number of strokes to the number of flashes.

C 17-102 -July 1995 -44 _.

B 2.2 Expected frequency Nd of direct lightning to a structure

The yearly average frequency Nd of direct lightning to a structure is assessed

using the following equation:

Nd:: Ng max .. Ae . C1 10-6/year, where: (Equation 6)

Ng is the yearJy average lightning flash density in the region where the structure is

located (number of lightning flashes/year/km2);

Ae is the equivalent collection area of the isolated struct~re (m2);

C1 is the environmental coefficient.

The equivalent collection area is defined as the ground area having the same

yearly direct lightning flash probability as the structure.

According to table 82, the equivalent collection area Ae for isolated structures is

defined as an area of ground surface which has the same annual frequency of

direct lightning as the structure. It is the area between the lines obtained by the

intersection of the ground surface and 1 :3 slope line passing through the top of

the structure and revolving around the structure (see figure 83).

For a rectangular structure with length L, width W an~ height H, the collection area

is then equal to :

Ae:: LW + 6H (L + W) + 9;rH2 (Equation 7)

The topography of the site and the objects located within the distance 3H from the

stru(;ture significantly affect the col!ection area. This effect is taken into account by

applying environmental coefficient C1 (table 82.).

Table 82 – Determination of environmental coefficient C1

– When the equivalent collection area of a structure entirelY.covers that of another

structure, the latter is disregarded.

– When the collection areas of several structures are overlapped, the

corresponding common collection area is considered as a single collection area.

Note: Other more sophisticated methods may be used to. assess the equivalent

collection area with greater accuracy.

C 17-102 -July 1995

Figures 83 – Typical computations

Note: Specific regulations may impose other values for Ne in some cases.

C 17-102 – July 1995 -48 –

B 3 PROTECTION LEVEL SELECTION METHOD

The tolerable lightning frequency Nc is compared with the expected lightning

frequency Nd.

The result of this comparison is used to decide whether an LPS is required and, if

so, the protection level to be used:

– If Nd ~ Nc, the LPSis not required systematically.

– If Nd > Nc• an LPS of effectiveness E ~ 1 – Nc/Nd should be installed and the

associated protection level selected in table 8 10.

The LPS design shall meet the specifications given in the standard for the selected

protection levels.·

When an LPS with an effectiveness factor E’ smaller than the computed factor Eis

installed, additional protective measures should be taken. Typical additional

protective measures are:

– measures limiting the step or contact voltage,

– measures restricting fire .propagation.

– measures reducing the effects of voltage surges induced by lightning on

sensitive equipment.

A practical method for selecting the protection level is given in fig!Jre 89.

Table 810 gives the critical effectiveness values Ec corresponding to the limits

between the protection levels and the protection levels corresponding to computed

effectiveness E.

– 49- I 17-102 ·July 1995

Table 89 – Determination of protection requirement and protection level

Result Data input Computation

area:

Figure 84 – Map of lightning stroke density Na in France

This map is based on statistical data coming from measures collected since 1987 by the

national network of lightning detection.

– 51 – C 17-102 • July 1995

APPENDIXC

(Normative)

E.S.E. LIGHTNING CONDUCTOR ASSESSMENT PROCEDURE

C 1 EXPERIMENTAL CONDITIONS

The effectiveness of an E.S.E. lightning conductor is assessed by comparing the

upward leader triggering time emitted by the E.S.E. lightning conductor against the

upward leader triggering time emitted by an S.R. lightning conductor.

For this purpose, the SR lightning conductor and E.S.E. lightning conductor are

assessed one after the other under the same electrical and geometrical conditions

during laboratory tests simulating the natural conditions of the upward leader

initiation (positive upward leader). .•

C 1.1 Ground field simulation

The natural ground field existing before a lightning stroke affects the conditions of

corona formation and of existing space charges. The natural ground field should

therefore be simulated: its value ranges from 10 kV/m to 25 kV/m.

C 1.2 Impulse field simulation

To reproduce the natural phenomenon as closely as possible, the ground field

bUild-up is simulated by a waveform the rise time of which ranges from 100 ~sec

. tsoho1u0ld00be~bseetcw.eeTnhe2.w10aaeafonrdm2.1s0l0g>Ve/mw/isthoin the. upward leader initiation region

C 2 EXPERIMENTAL seT-UP

C 2.1 Positions of lightning protection systems to ~e compared

The upper plate/air-termination distance should be sufficient for the upward leader

to propagate in free space and, in any case, over a length greater than 1 m (d ~

1m). The objects to be compared should be placed in the same electrical

environment which is independent of their locations : they should be tested one

after the other and centred on ground above the· plate and their height should be

the same.

C 2.2 Dimensions of experimental set-up

The upper plate/ground distance (H) should be greater than 2 m. The ratio h/H of

the air-termination height to the plate height above ground level should range from

0.25 to 0.5. The smaller horizontal dimension of the upper plate is the upper

plate/ground H distance.

C 17-102 -July 1995 ·52·

d

H

.PTS h

Configuration 1

Figure C1

Configuration 2

C 3 PARAMETERS TO BE CH~CKED – MEASUREMENTS TO BE TAKEN

C 3.1 Electrical parameters

– Applied voltage waveforms and amplitudes (ambient field calibration, pulsed

voltage wave, associated current, etc.);

– Continuous polarisation setting;

– Initiation setting on the reference equipment (simple rod lightning conductor) :

initiation probability equal to 1.

C 3.2 Geometrical conditions

The distance d should be strictly the same in each configuration : it should be

checked before each test.

C 3.3 Climatic parameters

The climatic conditions should be recorded before and after testing in each

configuration (pressure, temperature, absolute humidity).

C 3.4 Number of lightning strokes in each configuration

The number of lightning strokes should be statistically adequate in each

configuration, e.g. about one hundred lightning strokes in each configuration.

C 3.5 Triggering time

The criterion adopted for assessing the effectiveness of an E.S.E.lightning

conductor is its capacity to initiate an upward leader before an SR lightning

conductor under the same conditions. The average upward leader triggering time

T is measured for each usable lightning stroke on the SR lightning conductor and

then on the E.S.E. Iight~ing conductor.

– 53- C 17:’102-July 1995

· C4

C 4.1

EFFICIENCY OF THE E.S.E. LIGHTNING CONDUCTOR

Experimental Assessment of the average triggering times

The upward leader triggering times measured during usable shocks on an SR

lightning conductor and an E.S.E. lightning conductor are used to compute the

average triggering times T’SRLC and T’ESELC in compliance with the selected

experimental curve parameters.

C 4.2 Reference waveform

The reference waveform is defined by a rise time TR of 650 I-Isecand a shape as

shown in the graph of Figure C2.

C 17-102 – July 1995 – 54-

Reference waveform

C 17-102· july 1995

C 4.2 Determination of the triggering advance of the E.S.E. lightning conductor

The experimental curve is plotted on the same graph as the reference

waveform to which is assigned the same field value EM as the experimental

field EMexp.

Lines are dropped from T’SRlC and T’ESElC onto the rererence curve and the

ordinates of.the intersection points give the E field values. The triggering times

are obtained by projecting lines from the E values to the points where they

intersect the reference curve; the associated values on the x-axis gives the

triggering advance ~T (JJsec)= T’SRlC and T’ESElC’

Note : The method proposed above can be used to determine a AT value in a

laboratory. Using the upward leader initiation fields which only-depend on airtermination

height h, a tlT value independent of d can-be _determined. This

transposition is accomplished using the continuous leader starting threshold

field model developed by Rizk & Berger.

C 17-102 – July 1995 ·56·

APPENDIX D

(Informative)

TYPICAL LIGHTNING PARAMETERS AND ASSOCIATED EFFECTS

D 1 TYPICAL LIGHTNING PARAMETERS

D 1.1 . Impulse component waveforms (discharges) of a lightning stroke

Figure 01 shows a few lightning current waveforms. Such lightning currents

have been recorded at the San Salvatore Mount research station in

Switzerland. Tables 03 to 015 show the cumulated frequency distributions of

the lightning characteristics. .

Negative and positive lightning currents measured on San Salvatore Mount.at

lugano (Switzerland)

Figure D1 – Examples of lightning currents

D 1.2. Distribution of the different lightning parameters

A considerable number of parameters are used to describe the lightning

impulse (or impulses in case of negative lightning), including in particular: .

current amplitude, rise time, decay’time, charge and specific energy.

These parameters refer to the actual lightning stroke waveforms as measured

to compute the distribution statistics. Initially, the amplifude, decay time and rise

time may be considered as defined as in a laboratory. The charge corresponds

to f idt and the specific energy to I j2dt. The usefulness of these parameters is

explained below.

The steepness (steepest current slope in kNlJsec) is also sometimes a useful

data for characterising an impulse though it is related to other parameters

already defined: rise time and amplitude. .

C 17-102 – July 1995

The total lightning flash, including the impulse(s) and the following current

flowing in the interval between two impulses is essentially characterised by its

total duration.

02 THERMAL EFFECTS OF LIGHTNING PARAMETERS

The parameters mentioned in the foregoing do not generally have the same

effects or failure modes as regards the different types of equipment.

The current amplitude is useful for addressing the voltage surge problems and

mechanical load problems generated by lightning.

The rise time is only used to address the voltage surge problems.

The decay time is related to mechanical loads in that it is used to determine the

electromagnetic force application time; it is mainly representative of the

lightning stroke energy in connection with the amplitude. To represent this

energy, the amplitude/decay time binomial can be replaced by :

– Specific energy I j2dt (amplitude and decay time) when the LPS component

dimensions are considered (connectors, conductors, etc.);

– Charge I idt (amplitude and decay time) in the case of the characteristics of

surge protective devices connected to lightning protection systems (E.S.E.

lightning conductor + earth-termination system) -or metal melting at the

lightning strike point.

o 2.1 Thermal effects related to charge quantity Q

Thermal effects are observed in lightning protection inst::lll:Jtion:; especially

when the air-termination systems have sharp tips on· which melting is

sometimes observed over a maximum of a few millimetres. In the case of flat

surfaces (sheet-metal plates), evidence of melting is found which may result in

complete piercing.

An exceptional lightning stroke (300 C) is capable of piercing sheet-metal plates

of up to 2-3mm thick.

This accounts for the minimum thickness requirement when a metal plate is

used or likely to serve as a lightning collector (e.g., 4 mm for iron, 5 mm for

copper) ..

Low-intensity discharges with a long duration may readily ·cause ignition. As

lightning discharges are usually accompanied by a continuing current. lightning

strokes are seldom cold. Even dry wood can be ignited by this kind of lightning

with long-lasting continuing currel}ts.

Poor contacts are particularly dangerous points along the lightning current path.

Contact resistance values of a few thousandths of an ohm already generate

enough heat to melt appreciable quantities of metal producing sparks. When a

readily flammable material is located near such poor contact points, indirection

ignition may result. This kind of sparking is particularly dangerous in premises .

exposed to a risk of explosions and in explosive manufacturing plants.

C 17-102 – July 1995 – 58 –

«D 2.2

D 2.3

Thermal effects related to current integral J j2dt

When the lightning current enters a metal conductor in which it can propagate,

the resulting heat dissipation obeys the Joule’s law which involves the square of

the current i2, current flowing time t and ohmic resistance R.

Significant thermal effects are therefore encountered especially at highresistance

points.

The direct-current resistance measured on a conductor should not however be

taken as the resistance value R. Lightning currents are short shock waves

which produce a skin effect as in the case of high-frequency currents, Le., the

current flow is confined to a thin conductor surface layer a few tenths of a

millimetre thick, as measured in direct current, which corresponds to the total

cross-sectional area.

There are no visible consequences of this heating, in spite of the skin effect,

when the conductor gauge is large enough. Temperature rises up to the melting

point .temperature only occur in conductors having a small gauge or high

resistivity. Melting effects are often observed, for instance, in antenna cables

and wires. On the other hand, cases of melting are seldom observed on larger

gauge wires of a few millimetres in diameter (such a barbed wires). Melting has

never been seen in lightning conductors having the gauge recommended in this

standard.

On the other hand, the current flow in poor conductors releases a large amount

of energy in the form of heat. This is why the water contained in wood, concrete

and similar materials is heated up and vaporised. The entire phenomenon lasts

a very short time and, as a consequence of the subsequent pressure rise,

trees, wooden masts, beams and walls burst. Explosive effects of this kind

more particularly occur in places where mpisture has accumulated (slits,

vessels full of sap) or the current density has risen significantly, i.e., at the

points of current entry or exit between a material having a poor conductivity

(cement) and a material having a high conductivity (attaching clamps of a

damaged lightning down-conductor, electrical conduit cramps, water and gas

pipe steel clamps).

Electrodynamic effects

Significant mechanical loads may occur only when sections of the lightning

current path are laid out one relative to the other in such a way that one of them

is located within the magnetic field generated by the other. In this case, the load

increase is inversely proportional to the distance between these sections. Small

turns are subjected to considerable enlarging loads. Considering a 10 cm

diameter ring made of 8 mm diameter wire, a very heavy lightning current of

100 kA will apply a force of 1200N to each centimetre of the periphery. With a

2m» diameter, the for.ce would drop to 140N. Due to the reciprocal interaction

between the lightning current in a conductor and the Earth’s magnetic field,

mechanical effects of only about 10N per metre of conductor can be produced;

such effects are trivial.

– 59- C 17-102 -July 1995

In addition to these repulsion forces, which may distort conductors in rare

cases, there are also strong attraction forces between parallel lightning current

paths»when they are quite close. In this way, thin tubular antennae are crushed

and parallel conductors knock together.

D 2.4 Potential differences and arcing

The surprising profusion of spark traces observed after a violent lightning

stroke, sometimes even in buildings provided with lightning protectioR systems,

can be explained by two effects well known in electrical engineering : the earthtermination

potential rise, which mainly depends on the peak intensity

(amplitude) of the drained current, and the induction phenomena which mainly

depend on the dildt gradient (leading edge steepness) of this current.

D 2.4.1 Earth-termination potential rise

Due to the earth-termination resistance R, resulting from the resistivity of the

soil itself, there is a potential difference between the LPS down-conductor and

nearby points while the current is flowing. The total potential rise relative to the

unaffected remote «ground’ (therefore remaining at the conventional zero

potential) is expressed by Ohm’s law : U = RI

A 100 kA current flow through a 5-ohm earth-termination system will cause a

potential rise in the lightning current draining system of 500 kV relative to

remote ground points.

Such a potential rise is actually distributed in the ground according to a law

which depends on the type of earth-termination system and the soil

characteristics.

All the conductive parts of the structure which are connected to the earth in any

way (heating systems, pipe lines, electrical systems, cable armours) are also

subjected to a potential rise if they are not interconnected. The only way to

prevent insulation breakdown is to provide an electrical connection through

down-conductors to independently earthed parts. In thi~ way, these become

integral parts of the lightning protection system and can therefore drain part of

the lightning current according to branch circuit laws. Their connection to the

down-conductors make them an integral part of the LPS.

As no conductive connections to live electrical lines can be made, this standard

recommends the installation of voltage surge protective devices known as

lightning arresters (varistors or spark gaps). However, these lightning arresters

should then be sized to withstand a non-negligible portion (from a few per cent

up to 50 per cent, approximately, in the worst case) of the lightning current

striking the LPS.

Note : Given the frequencies involved in lightning phenomena, the earthtermination

system impedance should be taken into account in addition to the

measured earth-termination system direct-current resistance.

C 17-102 -July 1995 – 60-

D 2.4.2 Induction phenomena

Shorter ~istance between down-conductbr and metal building structures

An LPS down-conductor forms open loops with the various metal structures of

a building (water pipes, central heating system, electrical power lines, etc.).

These loops will be subjected to induction phenomena and electromotive ~orces

will appear between their open ends. This standard allows for this phenomena

in article 3.

TABLES 02 TO 014

These’tables are extracted from IEC 1024-1, Part 1, Se.ction 1, Guide A,

«Selection of protection levels for lightning protection systems»

Basic values of lightning current parameters

Cumulative frequency distribution

APPENDIX E

(Informative)

PROTECTING PEOPLE AGAINST ELECTRICAL SHOCKS

E 1 GENERAL

People standing outdoors run the greatest risk of being struck by lightning,

‘. whether directly or caused by the step voltage. For people inside a structure,

.the hazards are due to :

{a} the abrupt potential rise in items connected to lines leading from the

outside such as power lines, telephone lines, outdoor TV antenna cables;

(b) metal objects within the structure which may» also be brought to high

potentials : contact voltage.

The measures stated in this standard to prevent dangerous sparking are

designed to reduce the risks run by people inside structures.

E 2 PERSONAL BEHAVIOUR

To protect themselves against lightning, individuals should take the following

minimum precautions : .

(a) look for a shelter in a place covered by an earthed roof is or an all-metal

shelter.

Note: Conventionally manufactured tents do not provide protection ..

(b) when there is no shelter nearby, reduce one’s height (crouch down) and

surface area on the ground Goin the two feet) and do not touch any earthed

object with the hands, .

(c) do not ride a bicycle or a horse. Do not remain in an open-top car,

(d) do not walk or swim in water,

(e) keep away from high places, or tall or isolated trees. If the vicinity of a tree

cannot be avoided, stand beyond the foliage limits. .

(f) do not touch or stand next to metal structures, metal fences, etc.,

(g) do not carry any object which extends above the head (umbrella, golf club,

tool, etc.),

(h) do not use or minimise the use of cord telephones,

(i) do not touch any metal object, electrical appliances, window frames, radio

sets, TV sets, etc.

C 17-102 – July 1995 – 64-

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

considered.

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

2.2.5.1 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

2.2.5.1). –

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 –

2.2.5.2 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.

2.2.5.3 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 DOWN-CONDUCTORS

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 2.3.3.1.

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.

A

-19 – C 17-102 -July 1995

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

B

2.3.3

A

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

Routing

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.

2.3.3.1 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

building.

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.

2.3.3.2 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.

Down-conductors

Minimum dimeInsions Remarks

SRtreipco: m3m0exn2dmemd for its

Rgoooudndcosnedcutioctniv: ity8mamnddia.

Braided cable: 30×3.5mm

SRtericpo:m3m0~xn2dmemd in certain

environments.

RoUnd 8mm dia.

(2)

STotripb:e 3u0sxe3dmomn aluminium

Round section: 10mm dia.

(2)

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.

Notes:

(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.

2.3.7.1 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

less.

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

systems.

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.

2.3.7.2 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.

3. EQUJPOTENTIAL BONDING OF METAL PARTS AND

INTERNAL LIGHTNING PROTECTION INSTAllATION

3.1 GENERAL

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.

_ki

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

where:

(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

Notes:

(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.

3.2 EQUIPOTENTIAL BONDING OF EXTERNAL METAL MASSES

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,

s=3m.

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

device.

3.3 EQUIPOTENTIAL BONDING OF METAL PARTS SUNK INTO WALLS

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.

3.4 EQUIPOTENTIAL BONDING OF INTERNAL METAL PARTS: INTERNAL

LIGHTING PROTECTION INSTALLATION

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.

4. EARTH TERMINATION SYSTEMS

4.1 GENERAL

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 be.as 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.

4.2 EARTH TERMINATION SYSTEM TYPES

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

20-100

10-150

5-100

50

200

30-40

50-500

200-3000

1500-3000

300-500

.•

100-300

1000-5000

500-1000

300

800

1500-10000

600

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

connector

B

\Disconnectable

connector

D : Down-conductor

B : Building foundation loop earth

P : Lightning earth termination system

,.

Figure 4.2 – Typical earth termination system diagrams

4.3 ADDITIONAL MEASURE~

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.

4.4 EARTH TERMINATION SYSTEM INTERCONNECTION

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

purposes.

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

equipment.

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.

4.5 PROXIMITY REQUIREMENTS

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

tEearmrthinatetiromninastyiosntem

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.

4.6 MATERIALS AND DIMENSIONS

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

RecoMmimnimenudmatidoinmsensions

for the good

cRoonudnudctsiveictytioann:d8cmormrosdiioan.

Grid made of wire with a min.

cITSmIgruoomblsi2dusl-asstrearckoteido::na12l55mamrmemad0oia.f.0,1.01.m1m

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.).

5. ANTICORROSION PROTECTION

5.1 GENERAL

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.

5.2 PRECAUTIONS AND MEASURES TO BE TAKEN

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

influences.

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

examples:

– 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

down-conductors.

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

admitted.

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

material under corrosive environmental conditions.

6. SPECLl1.LMEASURES

6.1 ANTENNAE

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.

6.2 THATCHED ROOFS

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.

6.3 FACTORY CHIMNEYS

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.

6.4 FLAMMABLE AND EXPLOSIVE MATERIAL STORAGE AREAS

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.

6.5 RELIGIOUSBUILDINGS

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

terminal.

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

H~40m H>40m

Figure 6.5 – Religious building

– 35- C 17-102 -July 1995

.•6.6 STRUCTURES OF ALTITUDE

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.

6.7 OPEN AREAS, LEISURE OR SPORTS AREAS

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

standard.

6.8 TREES

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.

7. INSPECTION,MAINTENANCE

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.

Lightning protection Protection of structures and open areas against lightning using early streamer emission air terminals.Part 1

This standard provides information for the state-of-the-art design of a satisfactory lightning

protection system for structures (building, fixed facilities …) and open areas (storage areas,

leisure or sports areas …) using an early streamer emission lightning conductor and provides

instructions as to the methods to be used for achieving such protection.

As in the case with anything related to the natural elements, a lightning protection system,

designed and installed in accordance with this standard, cannot guarantee absolute

protection to structures, persons or objects; however, applying this standard will significantly

reduce the risk of protected structures being damaged by lightning. .

The decision to provide a structure with a lightning protection system depends on the

following factors: lightning stroke probability. severity and acceptable consequences. The

selection is based on the parameters contained in the risk assessment guide (Appendix B to

this standard). The risk assessment guide also indicates the appropriate protection level.

Examples of structures which may need a lightning protection system are:

buildings open to the publict

– tower blocks and, generally, high structures (pylons, water towers, lighthouses, etc.).

– buildings and warehouses containing dangerous materials (explosive, flammable or toxic

materials, etc.).

– buildings containing highly vulnerable or valuable equipment or documents (such as

telecommunication facilities, computers, archives, museums, historical monuments).

From the structure design stage onwards and then during the installation, particular attention

should be paid £0 ;

– take into consideration all the items which are to be used for making up a lightning

protection system which meets the requirements of this standard by requesting

professional advice from those involved in the sector : designers. builders, installers,

users, etc.

– plan the complementary use of conductive items in the structures to be protected.

The measures stated in this standard are the minimum requirements for a statistically

effective protection.

C 17-102 -July 1995 -2-

Contents

1. GENERAL.•……•…….•…………………………………………………….•………………….•.•…………………………..4

1.1 SCOPE AND .OBJECT 4

1.2 REFERENCE STANDARDS 4

1.3 DEFINITIONS 5

1.4 STORMY PHENOMENA AND LIGHTNING PROTECTION SYSTEM BY E.S.E. LIGHTNING

CONDUCTOR 7

2. EXTERNAL L1GHT~ING PROTECTION INSTALLATION (ELPI) ………………………………..••.. :….•• 10

2.1 GEN ERAL 10

2.2 AIR-TERMINATION SySTEMS 11

2.3 DOWN-CON DUCTORS 19

3. EQUIPOTENTIAL BONDING OF METAL PARTS AND INTERNAL LIGHTNING PROTECTION

INSTA LLA TI 0 N .•••.•••••••••••.••…•••.•.•..•.••••……•…………..•…•.•••••…..••…..•.••…•..•…………•…•…..•••..•…… 24

3.1 GEN ERAL 24

3.2 EQUIPOTENTlAL BONDING OF EXTERNAL METAL MASSES 26

3.3 EQUIPOTENTIAL BONDING OF METAL PARTS SUNK INTO WALLS 26

3.4 EQUIPOTENTIAL BONDING OF INTERNAL METAL PARTS : INTERNAL LIGHTING

PROTECTION INSTALLA TION ‘~ 27

4. -EARTH TERMINATION SYSTEMS .•..•.•••…•.•…….•….•••…..•••••….•………•…..•………….•..••.•.•••••.••.•…• 27

4.1 GEN ERAL 27

4.2 EARTH TERMINATION SYSTEM lYPES ………………………..•……………………………………………….. 28

4.3 ADDITIONAL MEASURES 30

4.4 EARTH TERMINATION SYSTEM INTERCONNECTION 30

4.5 PROXIMITY REQUIREMENTS 31

4.6 MATERIALS AN D DIMENSIONS 31

5. ANTICO RR OS10N PROTECTIO N .••………..•……………•.•.•..•….•………••……..•………….•………•…….•.. 32

5.1 GENERAL 32

5.2 PRECAUTIONS AND MEASURES TO BE TAKEN 32

6. SP ECIAL MEAS URES …••..•.•..••.•..•……….•………..•……….•..••.•..•….•….••…•…•………•….•..•…….•……… 33

6.1 ANTENNAE : 33

6.2 THATCHED ROOFS …..••; 34

6.3 FACTORY CHI MNEYS ‘» : -..:: 34

6.4 FLAMMABLE AND EXPLOSIVE MATERIAL STORAGE AREAS 34

6.5 RELIGIOUS BUI LDINGS 35

6.6 STR UCTU RES OF ALTITUDE 36

6.7 OPEN AREAS, LEISURE OR SPORTS AREAS 36

6.8 TREES : 3ef

7. INS PECTIO N. MAl NTENAN CE .•..•..•………..••…………..•••….••••….•..••……..•..••.•. :….•………•.•…••.•…..• 36

7.1 INITIAL INSP ECTlON 36

. 7.2 SCH EDULED INSP ECTION 37

7.3 MAl NTENANC E 38

AP PEN DIX A •••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••.•••••••••••••••••39

AP PEN DIX B •••••.•••••••••••••••••••••••.•••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••••~••••••••••••••••••••••••••••••••..• 43

AP PEN DIX C ••••••.•.••••••••••••••••••••••••••••••••••••••••••••••••••••••••..•••••••••••••••••••••••••••••••••••••••••••••••••.•••••.••••••••••.••••••• 52

AP PEN 0 IX D ••••••••••••••••••••••••••••••••••••••••••••.•••.•••••••••.•••••.••.••.•••••••••••••••••••••••.••••••••••••••••••••.•••••••••••..••••.•..•..• 57

AP PENDIX E •..••…••••.••..••.•••••…•……..••..•……….•…..•……….••.••••…..•.••.•..••…..•..•.•..•.•.••.•…….••..•…………….. 64

-3- C 17-102-July 1995

1.1

1.1.1

GENERAL

SCOPE AND OBJECT

Scope

This standard is applicable to the lightning protection using early streamer

emission lightning conductors of common structures of less than eO-m high and of

open areas (storage areas, leisure areas, etc.). It includes the protection against

the electrical consequences due to the lightning current flow through the lightning

protection system.

Notes:

1. This standard does not cover the protection of electrical equipment or systems

against voltage surges of atmospheric origin whidl are transmitted by networks

entering the structure.

2. Other standards describe lightning protection systems using simple rod

lightning conductors, stretched wires and meshed conductors.

Some Administrations. public services or operators of hazardous installations

may have adopted specific regulations.

1.1.2 Scope

This standard provides the information for the design. construction. inspection and

maintenance of lightning protection systems using early streamer emission

lightning conductors. The purpose of these lightning protection systems is to

safeguard persons and property as effectively as possible.

1.2 REFERENCE STANDARDS

The following standards contain provisions which are referred to herein and thus

applicable to this standard. At the time of publishing, the stated issues were

current. Any standard is subject to revision and the parties involved in agreements

based on these standards are urged wherever possible to use the latest issues of

the documents listed below:

NF C 15-100 (May 1991)

Installations electriques it basse tension: Regles

NF C 90-120 (October 1983)

Materiel electronique et de telecommunications – Antennes individuelles ou

collectives de radiodiffusion sonore ou visuelle : Reg.les

NF C 17-100 (February 1987)

Protection of structl:lres against lightning – Requirements.

C 17-102 – ..July 1995 .4·

-1.3 DEFINITIONS

1.3.1 Lightning flash to earth

An electrical discharge of atmospheric origin between cloud and earth, consisting

of one or more current impulses (return strokes).

1.3.2 Lightning stroke

One or more lightning discharges to earth.

1.3.3 Striking point

A point where a lightning stroke contacts the earth, a structure, or a lightning

protection system.

1.3.4 Protected volume

Volume of influence of the early streamer emission lightning conductor within

which the early streamer emission lightning conductor is the striking point.

1.3.5 Lightning flash density Ng

Yearly number of lightning flashes per km2•

1.3.6 Return stroke density Na

Yearly number of return strokes per km2• A lightning stroke consists, in average;

of several retrurn strokes. See map in Appendix B.

1.3.7 Lightning protection system (lPS)

The compl~te system used to protect structures and open areas against the

effects of lightning. It consists of an external lightning protection installation and of

an internal lightning protection installation, if any.

1.3.8 External lightning protection installation (ElPI)

An external lightning protection installation consits of an air-termination system,

one or more down-conductors, and one or more earth termination systems.

1.3.9 Internal lightning protection installation (ILPI)

An internal lightning protection installation consists of all the devices and

measures reducing the electromagnetic effects of lightning current within the

volume to be protected.

1.3.10 Early streamer emission (E.S.E.) lightning conductor

A lightning rod equipped with a system which Cieates the triggering advance of tile

upward leader when compared with a simple rad (SR.) lightning conductor in tthe

same conditicns.

– 5 – C 17-102 – July 1995

1.3.11 Triggering process

Physical phenomenon between the inception of the first corona and the continuous

propagation of an upward leader.

1.3.12 Triggering advance (.1. T)

Mean gain in triggering time of the upward leader of the E.S.E. lightning conductor

when compared with a S.R. lightning conductor in the same conditions and

derived from the evaluation test. This is expressed in ~s.

1.3.13 Natural component

A conductive part located outside the structure, sunk in the walls, or situated

inside a structure and which may be used to re~lace all or part of a dbwncondu~

tor or as a supplement to an ELPI.

1.3.14 Equipotential bonding bar

A collector used to connect the natural components, ground conductors, earth

conductors, screens, shields and conductors protecting electrical

telecommunication lines or other cables, to the lightning protection system.

1.3.15 Equipotential bonding

An electrical connection putting ground conductors and conductive parts at the

same potential or a substantially equal potential.

1.3.16 Equipotentiai conductor

A conductor providing for equipotential bonding.

1.3.17 Dangerous sparking

An electric arc produced by a lightning current within the volume to be protected.

1.3.18 Safety distance (5)

The minimum distance for which no dangerous spark can be produced.

1.3.19 Interconnected reinforcing steel

Natural components within a structure which provid~ an electrical path resistance

smaller than 0.01 nand can be used as down-conductors.

1.3.20 Down-conductor·

Part of the external lightning protection installation designed to conduct the

lightning current from the E.S.E.lightning conductor to the earth termination

system.

C 17-102 -July 1995 -6-

·1.3.21 Test joint/Disconnect terminal (or measurement terminal)

A device used to disconnect the earth termination system from the remainder of

the system.

1.3.22 Earth electrode

A part or group of parts of the earth termination system which provides direct

electrical contact with the earth and disperses the lightning current to earth.

1.3.23 Earth termination system

A conductive part or a group of conductive parts in intimate contact with and

providing an electrical connection with earth.

1.3.24 Earth termination system resistance

Resistance between the tes~ joint and earth : it equals the quotient of potential

increase, measured at the test joint with respect to an infinitely remote reference,

and of the applied current to the earth electrode.

1.3.25 Surge Protective Device (S.P.D.)

A device designed to limit transient surge voltages ~mdto provide a path for the

current waves. It contains at least one non linear component.

1.3.26 Transient surge voltage of atmospheric origin

Overvoltage lasting a few milliseconds only, oscillatory or not, usually strongly

damped.

1.3.27 Protection level

Classification of a lightning protection system which expresses its efficiency.

Note: This definition should not be confused with that used with surge protective

device (S.P.D.).

1.3.28 Equivalent collection area of a structure Ae

A flat ground surface subjected to the same number of Iigh~ning flashes as the

structure under consideration.

1.4 STORMY PHENOMENA AND LIGHTNING PROTECTION SYSTEM BY

E.S.E. LIGHTNING CONDUCTOR

1.4.1 The storm phenomena and the need for lightning protection

The need for protection is determined according to the lightning flash density of

the area being considered. The probability of a structure being struck by lightning

over a one-year period is the product of the lightning stroke frequency times its

equivalent collection area.

-7- C 11-102 -July 1995

1.4.2

The lightning flash density is given by the formula Ng = Na/2.2, Na is given in the

map situated in Appendix B. .

The structure protection appropriateness and the protection level to be used are

given in Appendix B.

Note : Other’ requirements (statutory requirements or personal considerations)

may lead to the decision being taken to adopt protection measures for reasons

other than statistical ones.

Characteristic lightning parameters and associated effects

Lightning is mainly characterised by parameters related to the electric arc between

the cloud and the ground, hence those related to the lightning current flow in the

arc and the conductors. ~

The most important parameters are the following:

– amplitude,

– rise time,

– decay time,

– current variation rate (di/dt),

– polarity,

– charge,

– specific energy,

-. number of strikes per discharge.

The first three parameters are independent in terms of statistics. Any amplitude

may be encountered, for instance, with any decay time (see the world-wide data

presented in the tables in Appendix D). –

As an electrical phenomenon, lightning may have the same consequences as any

other current flowing through an electrical conductor or any other current flow

through a bad conductor or an insulator.

The expected effects of the characteristic lightning parameters are as follows

– optical effects,

– acoustical effects,

– electro-chemical effects,

– thermal effects,

– electra-dynamic effects,

– electro-magnetic radiation.

The thermal and electro-dynamic effects are taken into account when sizing the

different components of the lightning protection system. The electro-magnetic

radiation effects (f1ashover, inductions, etc.) are taken into consideration in article

3.

The remaining effects have no appreciable effect on the design of a lightning

protection system. All the effects are described in Appendix D.

C 17-102 – July 1995 ·8-

1.4.3 Components of a lightning protection system

A lightning protection system consists of an external lightning protection

installation (ELPI) and. if necessary. of an additional internal lightning protection

installation (ILPI).

(bl

(iJ

(a)

(b)

. (d)

(fl

{k)

Figure 1.4.3

(f)

Cd)

le)

(t J

..

The external lightning protection installation consists of the following

interconnected items :

(a) One or more ESE lightning conductors

(b) One or more down-conductors

(c) A test joint for each down-conductor

(d) A lightning conductor earth electrode for each down-conductor

(e) Oisconnectable connector

(t) One or more connections between earths

(g) One or more equip-otential bounding .

(h) One or more equipotential bounding through antenna mast arrester

– 9· C 17-102 – July 1995

The internal lightning protection installation consists of:

(i) One or more equipotential bonding(s)

m One or more equipotential bonding bar(s)

The equipment of the electrical installation are:

(k) Earth termination of the structure

(I) Main earth terminal

(m) One or more surge protective device(s).

2. EXTERNALLIGHTNINGPROTECTIONINSTALLATION (ELPI)

2.1 GENERAL

2.1.1 Design

A prior survey should be conducted to determine the protection level to be

considered, the E.S.E. lightning conductor location(s), the down-conductor path(s),

the earth termination system location(s) and type(s).

Architectural constraints may be taken into account in the lightning protection

system design but this may substantially reduce the lightning protection system

effectiveness.

2.1.2 Prior survey

The prior survey is divided into two parts:

(a) Assessment of the lightning strike probability and selecting the protection level

using the datc! in Appendix B.

(b) Location of all the elements of the lightning protection installation.

This information should take the form of a specification, stipulating:

– structure sizes,

– relative geographical position of the structure: isolated, on a hilltop, amidst other

buildings which are higher, of the same height or lower, .

– frequency with· which the structure is occupied by people whose mobility is

restricted or othelWise,

– risk of panic,

– difficulty of access,

– service continuity,

C 17-102 -July 1995 -10 –

– structure confents : presence of persons, animals, flammable materials, sensitive

equipment such as computers, electronic or high-value or irreplaceable

apparatus,

– roof shapes and slopes,

– roof, wall and load-bearing structure types,

– metal parts or the roof and large external metal items, such as gas heaters, fans,

stairs, antennae, water tanks,

– roof gutters and rainwater pipes,

– salient building parts and types of materials (metal or non-conductive material),

– most vulnerable points of the building,

– lay-out of the building metal pipes (water, electricity, gas, etc.),

– nearby obstacles which may affect the lightning path, such as overhead electrical

lines, metal fences, trees, etc.,

– environmental conditions which may be highly corrosive (salt air; petrochemical

plant, cement works, etc.). .

The structural points considered as vulnerable are. the salient parts, particularly

towers or spires, chimney stacks and flues, roof gutters, edges, metal masses (air

exhausters, main wall cleaning system, guardrails, etc.), staircases, equipment

rooms on flat roofs.

2.2· AIR-TERMINATION SYSTEMS

2.2.1 General principles

An early streamer emission lightning conductor consists of a pointed air terminal, a

triggering device and a support rod with a down-conductor connecting system.

The area protected by an E.S.E. lightning conductor can be determined using the

electro-geometrical model, such as the one used in Appendix A, and the E.S.E.

lightning conductor triggering advance as defined in 2.2.2.

The E.S.E. lightning conductor should preferably be installed on the highest point

of the supporting structure. It should always be the highest point within the area

that it protects.

2.2.2 Triggering advance

An E.S.E. lightniQg conductor is characterised by its triggering advance which is

demonstrated during evaluation tests. Such tests compare an early streamer

emission lightning conductor against a simple rod lightning conductor situated in

the same conditions.

-11 –

The triggering advance (~T) is used for computing the protection radius. This is

expressed as follows:

tJ.T = TSR – TE.S.E. lightning conductor, where:

TSR is the mean triggering time of the upward leader of a simple rod lightning

conductor.

TE.S.E. is the mean triggering time of the upward leader of a ESE lightning

conductor.

2.2.2.1 E.S.E. lightning conductor evaluation test

This test procedure involves assessing, the triggering advance of an E.S.E.

lightning conductor. The natural conditions are simulated in the high-voltage

laboratory by adding the superimposition of a permanent field, representative of

the ambient field during a storm, and of·.an impulse field, representative of the

.downward leader approach. .

Note: In-situ correlation tests are in the process of being defined.

2.2.3 Positioning of the E.S.E. lightning conductor

2.2.3.1 Protected area

The protected area is delineated by the envelope of revolution having the same

axis as the E.S.E. lightning conductor and defined by the protection radii

corresponding the different heights h under consideration (see figure 2.2.3.1).

Figure 2.2.3.1. Protection radii

hn is the height of the E.S.E. lightning conductor tip relative to the horizontal

plane passing through the top of the element to be protected.

C 17-102 – July 1995 – 12 –

RPn is the E.S.E. lightning conductor protection radius at the height under

consideration.

2.2.3.2 Protection radius

The protection radius of an E.S.E. lightning conductor is related to its height (h)

relative to the area to be protected, to its triggering advance and to the selected

protection leve’!. (See Appendix A.).

Rp = ~h{2D ~h) + ~L{2D + ~L) with h ~ Srn. (Equation 1)

When h < Srn, the graphic method is applied using the curves in 2.2.3.3.a, band c.

Rp is the protection radius.

. .

h is the E.S.E. lightning conductor tip height relative to the horizontal plane

passing through the top of th~ element to be protected.

o is :

20m for protection level I,

4Sm for protection level 11,

SOmfor protection level Ill.

~L :’~L(m) = V(m/~s) . ~T(~S), where: (Equation 2)

AT is the triggering advance determined by the evaluation tests (see 2.2.2.1) as

defined in Appendix C.

2.2.3.3 Selection and positioning of an E.S.E. lightning conductor.

A prior survey is conducted to determine the required protection level (see para.

2.1.2) for each lightning protection system installation.

The required protection radius Rp for the protection of the structure is thendetermined

using equation 1 or the curves in figures 2.2.3.3.a, b, c for h ~ Sm, and

using the curves in figures 2.2.3.3. a), b) or c) for h < Sm for protection levels I to

III as follows : .

. – level I : graph of figure 2.2.3.3.(a)

-level 11 : graph of figure 2.2.3.3.(b)

-level III : graph of figure 2.2.3.3.(c) .

When the graphs are used, the protection radius Rp is determined by locating

required height h and ~L for the E.S.E. lightning conductor under consideration in

the appropriate graph:

Note: The ~L values in the graphs are non-restrictive examples.

-13 – C 17-102 -Jury 1995

0= 20 m

50

: ! !

; ! !

60

~ Le m >= 5 10 15 20 25 30 35 40 L, 5

Radii of protection for h = 20 to 60 m

20 10 20 _ …. 30 L,O 50

c::17·102 • July 1995 -14 –

20

hem)

o (m) is the striking distance or rolling sphere radius.

ol(m} is the triggering advance of the E.S.E. lightning conductor considered.

h(m) is the height difference between the air terminal tip and the horizontal plane

considered.

Rp(m} is the p’rotection radius in the horizontal plane considered.

Figure 2.2.3.3. (a)

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

Level of protection I (0 = 20 m)

~D=45m

i 0 10 _ 20 30 .. 1.0 50 60 70 80 90 100

L\L(m)= 510 152025 30351.0 loS 50

-15 – ,C 17-102 -July 1995

Radii of protection for h = 20 to 60m

o (m)

~L(m45)

1434123500505050 5

Rp (m)

478578963415014605.83..2945670309491456089

48758967527267127.18..64578028321657583

48578967538838.27…6057823409714895782

4785896785494949.49..341423901764738

478567959494494.7..87887545891237

586795670050505.0.000

5867956700505505.0…0000000

586789576050505.0.00

56895670050505.0.000

o (m) is the striking distance or rolling sphere radius.

~L(m) is the triggeri!1g advance of the E.S.E. lightning conductor considered.

h(m) is the height difference between the air terminal tip and the horizontal plane

considered.

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

Figure 2.2.3.3. (b)

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

Level of protection 11(0 = 45 m)

c 17:102 – July 1995 – 16 –

O=60m

hvn> LlL(m)=5101520253035L.04550

Radii of protection for h :: 20 to 60m

Norma Oficial Mexicana de Emergencia Sistemas de Medición de Energía Eléctrica. Especificaciones y métodos de prueba de Medidores Multifunción y Transformadores de Instrumento.

Participación del Regulador, Suministrador, Centro Nacional de Control de Energía, Transportista / Distribuidor, Usuarios.

  • Objetivo y alcance de la NOM de emergencia.
  • Justificación de la emergencia.
  • Marco jurídico, obligaciones y delimitación de responsabilidades.
  • Proceso metrológico, instrumentos de medición de energía eléctrica.
  • Revisión, pruebas y aseguramiento.
  • Protocolo de Verificación.
  • Conclusiones.

Objetivo y alcance de la NOM de emergencia

A partir del anteproyecto de NOM, Instrumentos Metrológicos, Sector eléctrico parte 2
(del grupo de trabajo radicado en el CCNNE) y de:
– Especificación CFE G0000-48, 2010
– NMX relacionadas con Transformadores de instrumento.

Establece las características físicas y condiciones mínimas aceptables de funcionamiento, métodos de prueba.

Conforma el espectro o menú de opciones tecnológicas aprobadas para su uso, definiendo una estratificación de funciones conforme a tipo de usurario.

No incluye sistemas de comunicación

Sistema delimitado por los siguientes elementos:
– Medidor de energía eléctrica
– Transformadores de instrumentación de Potencial (Tensión), (TP).
– Transformadores de instrumentación de Corriente, (TC).
– Instalaciones inherentes

Justificación de la emergencia

Riesgo de afectaciones económicas a los suministradores y usuarios (centrales eléctricas y centros de carga)

Riesgo de constituir barreras técnicas injustificadas a la industria eléctrica

No se cuenta con Norma Oficial Mexica en la materia (NOM ordinaria)

Al menos ocho meses para la emisión de la NOM ordinaria o definitiva
Aprobación previa del Comité de Normalización.- 75 días
Publicación para consulta pública.- 60 días,
Respuesta a comentarios 45 días,
Periodo de entrada en vigor una vez emitida.- 60 días

Marco jurídico, obligaciones y delimitación de responsabilidades

Artículo 3, fracción XVIII (LFSMN).- Verificación: la constatación ocular o comprobación mediante muestreo, medición, pruebas de laboratorio, o examen de documentos que se realizan para evaluar la conformidad en un momento determinado.

Artículo 73 (LFSMN).- “Las dependencias competentes establecerán, tratándose de las normas oficiales mexicanas, los procedimientos para la evaluación de la conformidad cuando para fines oficiales requieran comprobar el cumplimiento con las mismas, lo que se hará según el nivel de riesgo o de protección necesarios…”

Artículo 74 (LFSMN), 2do párrafo.- La evaluación de la conformidad podrá realizarse por tipo, línea, lote o partida de productos, o por sistema, ya sea directamente en las instalaciones que correspondan o durante el desarrollo de las actividades, servicios o procesos de que se trate, y auxiliarse de terceros especialistas en la materia que corresponda.

Artículo 133 (LIE).- Para certificar el cumplimiento de las normas oficiales mexicanas, las unidades de verificación a que se refiere el artículo 33 de esta Ley deberán ser acreditadas en los términos de la Ley Federal sobre Metrología y Normalización.
Por su parte, las unidades de inspección podrán certificar el cumplimiento de especificaciones técnicas, características específicas de la infraestructura requerida y otros estándares. Dichas unidades deben contar con la aprobación de la Comisión Reguladora de Energía.

Artículo 134 (LIE).- Los organismos de certificación, los laboratorios de pruebas, las unidades de verificación y las unidades de inspección que realicen sus actividades para la industria eléctrica observarán la estricta separación legal a que se refiere el artículo 8 de esta Ley.

Artículo 41 (LIE).- Los Transportistas y los Distribuidores sólo podrán suspender el servicio a los Usuarios Finales en los casos siguientes:

Por caso fortuito y fuerza mayor;
Por mantenimiento programado en las instalaciones, siempre que se haya notificado con anterioridad al Usuario Final o su representante;
Por incumplimiento de las obligaciones de pago o de garantía de un Usuario Calificado Participante del Mercado frente al CENACE, en cuyo caso el CENACE emitirá la instrucción respectiva;
Por incumplimiento de las obligaciones de pago oportuno por el servicio prestado, en cuyo caso el Suministrador que representa al Centro de Carga emitirá la instrucción respectiva;
Por terminación del contrato de Participante del Mercado o del contrato de Suministro, en cuyo caso el CENACE o el Suministrador que representa al Centro de Carga, respectivamente, emitirá la instrucción;
Por realizar actividades o incurrir en omisiones que impidan el funcionamiento adecuado de las redes o que alteren o impidan el funcionamiento normal de los instrumentos de control o de medición;
Por incumplimiento de las normas oficiales mexicanas, o mala operación o fallas en las instalaciones del Usuario Final;

Artículo 37 (RLIE).- El Servicio Público de Transmisión y Distribución de Energía Eléctrica se sujetará a las disposiciones administrativas de carácter general que emita la CRE en materia de Calidad, Confiabilidad, Continuidad, seguridad y sustentabilidad. La prestación de dicho servicio público se realizará observando el correcto funcionamiento e integridad de los equipos y dispositivos de sus redes. El Servicio Público de Transmisión y Distribución de Energía Eléctrica deberá prestarse bajo parámetros aceptables de:
I. Tensión;
II. Disponibilidad de los elementos de las redes;
III. Interrupciones del Suministro Eléctrico;
IV. Componentes armónicos;
V. Pérdidas de energía eléctrica, y
VI. Cualquier otro aspecto técnico que la CRE considere necesario.
Para efectos de lo anterior, al definir los parámetros que se determinen como aceptables, la CRE deberá tomar en cuenta los aspectos económicos asociados.

Artículo 113 (RLIE).- Los Transportistas y Distribuidores deberán usar e instalar únicamente instrumentos de medición que hayan obtenido una aprobación de modelo prototipo conforme a lo dispuesto por la Ley Federal sobre Metrología y Normalización y la norma oficial mexicana correspondiente y, en ausencia de ésta, conforme a la norma mexicana o norma internacional

Los Transportistas y Distribuidores deberán verificar a través de unidades de verificación acreditadas y aprobadas, cuando menos una vez cada tres años, los instrumentos de medición instalados para asegurar que se ajusten a la exactitud establecida en la norma oficial mexicana y en ausencia de ésta conforme a la correspondiente de acuerdo a lo señalado en el párrafo anterior.

Los Transportistas y Distribuidores deberán retirar los instrumentos de medición que no puedan ser calibrados para asegurar la exactitud establecida en la norma correspondiente y sustituirlos por los que cumplan con la misma.

Artículo 87-A (LFSMN).- La Secretaría (Economía), por sí o a solicitud de cualquier dependencia competente o interesado, podrá concertar acuerdos con instituciones oficiales extranjeras e internacionales para el reconocimiento mutuo de los resultados de la evaluación de la conformidad (informe de pruebas y/o certificados) que se lleve a cabo por las dependencias, personas acreditadas e instituciones mencionadas, así como de las acreditaciones otorgadas.

Las entidades de acreditación y las personas acreditadas también podrán concertar acuerdos con las instituciones señaladas u otras entidades privadas, para lo cual requerirán el visto bueno de la Secretaría.

Cuando tales acuerdos tengan alguna relación con las normas oficiales mexicanas, se requerirá, además, la aprobación del acuerdo por la dependencia competente que expidió la norma en cuestión y la publicación de un extracto del mismo en el Diario Oficial de la Federación.

NOM-022 pararrayos y tierras fisicas

NOM-022: PARARRAYOS Y TIERRAS FÍSICAS (01/04/16)

Norma Oficial Mexicana NOM-022-STPS-2015, Electricidad estática en los centros de trabajo-
Condiciones de seguridad.
Al margen un sello con el Escudo Nacional, que dice: Estados Unidos Mexicanos.- Secretaría del
Trabajo y Previsión Social
JESÚS ALFONSO NAVARRETE PRIDA, Secretario del Trabajo y Previsión Social, con fundamento
en los artículos 40, fracciones I y XI, de la Ley Orgánica de la Administración Pública Federal; 512,
523, fracción I, 524 y 527, último párrafo, de la Ley Federal del Trabajo; 1o., 3o., fracción XI, 38,
fracción II, 40, fracción VII, 41, 47, fracción IV, 51, primer párrafo, 62, 68 y 87 de la Ley Federal sobre
Metrología y Normalización; 28 del Reglamento de la Ley Federal sobre Metrología y Normalización;
5, fracción III, 7 fracciones I, III, VI, VII, X, XI, XII, XIV, XV, XIX y XX, 10 y 29, del Reglamento
Federal de Seguridad y Salud en el Trabajo, y 5, fracción III, y 24 del Reglamento Interior de la
Secretaría del Trabajo y Previsión Social,
CONSIDERANDO
Que conforme a lo previsto por el artículo 46, fracción I, de la Ley Federal sobre Metrología y
Normalización, la Secretaría del Trabajo y Previsión Social presentó ante el Comité Consultivo
Nacional de Normalización de Seguridad y Salud en el Trabajo, en su Décima Segunda Sesión
Ordinaria, celebrada el 9 de diciembre de 2014, el Proyecto de modificación de la Norma Oficial
Mexicana NOM-022-STPS-2008, Electricidad estática en los centros de trabajo-Condiciones de
seguridad, para quedar como PROY-NOM-022-STPS-2014, Electricidad estática en los centros de
trabajo-Condiciones de seguridad, y que el citado Comité lo consideró procedente y acordó que se
publicara como Proyecto en el Diario Oficial de la Federación;
Que de acuerdo con lo que determinan los artículos 69-E y 69-H, de la Ley Federal de Procedimiento
Administrativo, el Proyecto correspondiente fue sometido a la consideración de la Comisión Federal de
Mejora Regulatoria, quien dictaminó favorablemente en relación con el mismo;
Que de conformidad con lo señalado por el artículo 47, fracción I, de la Ley Federal sobre Metrología y
Normalización, se publicó para consulta pública por sesenta días naturales en el Diario Oficial de la
Federación de 6 de enero de 2015, el Proyecto de modificación de la Norma Oficial Mexicana NOM-
022-STPS-2008, Electricidad estática en los centros de trabajo-Condiciones de seguridad, para quedar
como PROY-NOM-022-STPS-2014, Electricidad estática en los centros de trabajo-Condiciones de
seguridad, a efecto de que en dicho periodo los interesados presentaran sus comentarios al Comité
Consultivo Nacional deNormalización de Seguridad y Salud en el Trabajo;
Que habiendo recibido comentarios de diez promoventes, el Comité referido procedió a su estudio y
resolvió oportunamente sobre los mismos, por lo que esta dependencia publicó las respuestas
respectivas en el Diario Oficial de la Federación de 20 de agosto de 2015, con base en lo que dispone el
artículo 47, fracción III, de la Ley Federal sobre Metrología y Normalización;
Que derivado de la incorporación de los comentarios presentados al Proyecto modificación de la
Norma Oficial Mexicana NOM-022-STPS-2008, Electricidad estática en los centros de trabajo-
Condiciones de seguridad, para quedar como PROY-NOM-022-STPS-2014, Electricidad estática en los
centros de trabajo-Condiciones de seguridad, así como de la revisión final del propio proyecto, se
realizaron diversas modificaciones con el propósito de dar claridad, congruencia y certeza jurídica en
cuanto a las disposiciones que aplican en los centros de trabajo, y que en atención a las anteriores
consideraciones, y toda vez que el Comité Consultivo Nacional de Normalización de Seguridad y Salud
en el Trabajo, en su Tercera Sesión Ordinaria de 2015, otorgó la aprobación respectiva, se expide la
siguiente:
NORMA OFICIAL MEXICANA NOM-022-STPS-2015, ELECTRICIDAD ESTÁTICA EN LOS
CENTROS DE TRABAJO-CONDICIONES DE SEGURIDAD
INDICE

  1. Objetivo
  2. Campo de aplicación
  3. Referencias
  4. Definiciones
  5. Obligaciones del patrón
  6. Obligaciones de los trabajadores
  7. Condiciones de seguridad
  8. Sistema de protección contra descargas eléctricas atmosféricas
  9. Medición de la resistencia a tierra de la red de puesta a tierra
  10. Capacitación y adiestramiento
  11. Unidades de verificación y laboratorios de prueba
  12. Procedimiento para la Evaluación de la Conformidad
  13. Vigilancia
  14. Bibliografía
  15. Concordancia con normas internacionales
    TRANSITORIOS
    GUÍA DE REFERENCIA I. Ejemplos de instalaciones donde se presenta la generación de
    electricidad estática y medidas tendientes a prevenir accidentes, y casos ejemplo en los que se sugiere
    considerar la instalación de un sistema de protección contra descargas atmosféricas.
  16. Objetivo
    Establecer las condiciones de seguridad en los centros de trabajo para prevenir los riesgos por
    electricidad estática, así como por descargas eléctricas atmosféricas.
  17. Campo de aplicación
    2.1 Esta Norma rige en todo el territorio nacional y aplica en las áreas de los centros de trabajo donde
    se almacenen, manejen o transporten sustancias inflamables o explosivas, o en aquellas en que, por la
    naturaleza de sus procesos, materiales y equipos, sean capaces de almacenar o generar cargas eléctricas
    estáticas.
    2.2 La presente Norma no aplica en vehículos automotores, ferroviarios, embarcaciones y/o aeronaves
    utilizados para el transporte terrestre, marítimo, fluvial o aéreo, competencia de la Secretaría de
    Comunicaciones y Transportes.
  18. Referencias
    Para la correcta aplicación de esta Norma se deberán consultar las siguientes normas oficiales
    mexicanas y la norma mexicana, vigentes o las que las sustituyan:
    3.1 NOM-002-STPS-2010, Condiciones de seguridad – Prevención y protección contra incendios en los
    centros de trabajo.
    3.2 NOM-017-STPS-2008, Equipo de protección personal – Selección, uso y manejo en los centros de
    trabajo.
    3.3 NOM-018-STPS-2000, Sistema para la identificación y comunicación de peligros y riesgos por
    sustancias químicas peligrosas en los centros de trabajo.
    3.4 NOM-026-STPS-2008, Colores y señales de seguridad e higiene, e identificación de riesgos por
    fluidos conducidos en tuberías.
    3.5 NMX-J-549-ANCE-2005, Sistema de protección contra tormentas eléctricas – Especificaciones,
    materiales y métodos de medición.
  19. Definiciones
    Para efectos de la presente Norma, se consideran las definiciones siguientes:
    4.1 Autoridad laboral: Las unidades administrativas competentes de la Secretaría del Trabajo y
    Previsión Social que realizan funciones de inspección y vigilancia en materia de seguridad y salud en el
    trabajo, y las correspondientes de las entidades federativas y de la Ciudad de México, que actúen en
    auxilio de aquéllas.
    4.2 Carga eléctrica estática: La propiedad física de la materia que se manifiesta por la pérdida o
    ganancia de electrones, generalmente en materiales aislantes de la electricidad, o materiales
    conductores aislados de tierra, que han estado en contacto o bajo presión.
    4.3 Conexión a tierra; Puesta a tierra: La acción y efecto de conectar eléctricamente uno o más
    elementos de un equipo o circuito a un electrodo o a un sistema de puesta a tierra, de tal forma que se
    encuentren a potencial eléctrico cero (0).
    4.4 Corriente de rayo: La corriente que circula al punto en donde el rayo hace contacto con la tierra (a
    una estructura o a los elementos constitutivos del sistema de protección contra descargas eléctricas
    atmosféricas), asociada con el proceso súbito de neutralización de la carga de la nube, a través de un
    flujo de electrones en el canal ionizado mediante el que se realiza el movimiento de la carga de la nube
    a tierra, formado por descargas discontinuas en aire.
    4.5 Descarga eléctrica: El flujo de corriente generada entre dos cuerpos con diferencia de potencial
    cuando se rompe el dieléctrico del aire entre ambos.
    4.6 Descarga eléctrica atmosférica: La transferencia de cargas eléctricas entre nube y nube, o nube a
    tierra.
    4.7 Densidad del rayo a tierra: El número de rayos que inciden a tierra por kilómetro cuadrado por año,
    en una región específica.
    4.8 Electricidad estática: Las cargas eléctricas que se generan y almacenan en los materiales sólidos,
    partículas o fluidos.
    4.9 Electrodo(s) de puesta a tierra; Electrodo(s) de la red de puesta a tierra: El (los) elemento(s)
    metálico(s) enterrado(s) que establece(n) una conexión eléctrica a tierra.
    4.10 Pararrayos; Terminal aérea: Los elementos metálicos cuya función es ofrecer un punto de
    incidencia para recibir la descarga atmosférica.
    4.11 Red de puesta a tierra; Sistema de puesta a tierra: El conjunto de conductores y conexiones,
    electrodo o electrodos, accesorios y otros elementos metálicos enterrados que interconectados entre sí
    tienen por objeto drenar a tierra las corrientes de un rayo y las generadas por las cargas eléctricas
    estáticas.
    4.12 Sistema de protección contra descargas eléctricas atmosféricas: El conjunto de elementos
    utilizados para proteger un área contra el efecto de las descargas eléctricas atmosféricas. Este conjunto
    está compuesto de un sistema externo y de un sistema interno de protección, con base en lo siguiente:
    a) Sistema externo de protección contra descargas eléctricas atmosféricas; Sistema de pararrayos: El
    conjunto de elementos para interceptar (terminales aéreas), conducir (conductores de bajada) y disipar
    (red de puesta a tierra) en forma eficiente la corriente de rayo, y
    b) Sistema interno de protección contra descargas eléctricas atmosféricas: El conjunto de elementos
    formado por todas aquellas medidas de protección que permiten reducir el riesgo de daño a los
    trabajadores e instalaciones del centro de trabajo, mediante la puesta a
    tierra, unión equipotencial, blindaje electromagnético, y supresores para sobretensiones.
    4.13 Unión eléctrica; Conexión equipotencial: La conexión permanente de partes metálicas para formar
    una trayectoria eléctricamente conductora que asegure la continuidad y capacidad de conducir, de
    forma que se encuentren al mismo potencial eléctrico.
  20. Obligaciones del patrón
    5.1 Establecer las condiciones de seguridad para controlar la generación y/o acumulación de las cargas
    eléctricas estáticas en las áreas del centro de trabajo, conforme a lo que prevé el Capítulo 7 de esta
    Norma.
    5.2 Instalar un sistema de protección contra descargas eléctricas atmosféricas en las áreas o
    instalaciones de los centros de trabajo donde se almacenen, manejen o transporten sustancias
    inflamables o explosivas, de acuerdo con lo determinado en el Capítulo 8 de la presente Norma.
    5.3 Medir la resistencia a tierra de la red de puesta a tierra, de conformidad con lo que señala el
    Capítulo 9 de esta Norma, comprobar la continuidad en los puntos de conexión a tierra, y en su caso,
    medir la humedad relativa cuando ésta sea una medida para controlar la generación y acumulación de
    cargas eléctricas estáticas, con base en lo dispuesto por el numeral 7.3 de la presente Norma.
    5.4 Informar a todos los trabajadores y a la Comisión de Seguridad e Higiene, sobre los riesgos que
    representa la electricidad estática y la manera de evitarlos, en su caso, considerar a los contratistas,
    proveedores y visitantes.
    5.5 Capacitar y adiestrar a los trabajadores sobre las técnicas para descargar o evitar la generación y
    acumulación de electricidad estática, conforme a lo que establece el Capítulo 10 de esta Norma.
    5.6 Registrar los valores de la resistencia de la red de puesta a tierra, la comprobación de la continuidad
    eléctrica y, en su caso, de la humedad relativa, de acuerdo con lo previsto por los numerales 9.5 y 7.3,
    inciso a), respectivamente, de la presente Norma.
    5.7 Exhibir ante la autoridad laboral, cuando así lo solicite, la información y documentación que esta
    Norma le obligue a elaborar o poseer.
  21. Obligaciones de los trabajadores
    6.1 Observar las medidas de seguridad previstas en la presente Norma, así como las que se establezcan
    en el centro de trabajo para la prevención de riesgos por generación y acumulación de electricidad
    estática.
    6.2 Participar en la capacitación y adiestramiento que el patrón les proporcione.
    6.3 Notificar al patrón, de conformidad con el procedimiento que para tal efecto se establezca,
    cualquier situación anormal que detecten en los sistemas de puesta a tierra y sistema de protección
    contra descargas eléctricas atmosféricas.
  22. Condiciones de seguridad
    7.1 Las condiciones de seguridad para controlar la generación y/o acumulación de electricidad estática,
    se deberán determinar con base en lo siguiente:
    a) La naturaleza del trabajo (se refiere a las etapas del proceso, los equipos, la existencia de fricción,
    la velocidad de conducción o vertido de fluidos y los tipos de procedimientos de trabajo, entre otras
    características);
    b) Las características fisicoquímicas de las sustancias (temperatura, punto de inflamación, límite de
    explosividad, viscosidad, conductividad específica de la sustancia, densidad, entre otras), que se
    manejen, almacenen o transporten;
    c) Las características del ambiente en lo que se refiere a humedad relativa y temperatura, y
    d) Las características de los materiales de construcción de la maquinaria, equipo e inmueble.
    7.2 Para controlar la generación o acumulación de electricidad estática se deberán adoptar, según
    apliquen, las medidas de seguridad siguientes:
    a) Instalar sistemas de puesta a tierra, dispositivos o equipos para controlar la electricidad estática, en
    función de los tipos de procesos e instalaciones con que se cuente, tales como: ionizadores;
    neutralizadores o eliminadores de electricidad estática; dispositivos con conexión a tierra; cepillos
    mecánicos conectados a tierra; barras de disipación de electricidad estática, o mediante la aplicación de
    tratamientos a bandas, entre otros;
    b) Asegurar la unión eléctrica o conexión equipotencial entre máquinas, equipos, contenedores y
    componentes metálicos;
    c) Realizar la medición de la resistencia a tierra de la red de puesta a tierra, conforme a lo señalado
    por el Capítulo 9 de la presente Norma, y la comprobación de la continuidad en los puntos de conexión
    a tierra, al menos cada doce meses. Los valores deberán cumplir con lo siguiente:
    1) Tener un valor menor o igual a 10 ohms, para la resistencia a tierra del (los) electrodo(s) en
    sistemas de pararrayos o sistema de protección contra descargas eléctricas atmosféricas;
    2) Tener un valor menor o igual a 25 ohms, para la resistencia a tierra de la red de puesta a tierra, y
    3) Existir continuidad eléctrica en los puntos de conexión a tierra del equipo que pueda generar o
    almacenar electricidad estática. En la Guía de referencia I, se indican de manera ilustrativa los puntos a
    inspeccionar y la forma de medir la continuidad eléctrica de las conexiones;
    d) Colocar pisos antiestáticos o conductivos;
    e) Humidificar el ambiente manteniendo una humedad relativa superior a 65%. Esta disposición no
    aplica para aquellos casos en que, por la naturaleza de las sustancias, la humedad del aire represente un
    peligro por reacción con la sustancia, en cuyo caso el control de la acumulación de la electricidad
    estática se deberá realizar por otros medios;
    f) Ionizar el aire en la proximidad del equipo, contenedor u objeto cargados, y/o
    g) Aumentar la conductividad de los materiales susceptibles de generar y acumular cargas eléctricas
    estáticas, mediante el agregado de aditivos conductivos (por ejemplo, negro de humo, aditivos de
    carbono, grafito y otros productos conductores de la electricidad).
    7.3 En las áreas de trabajo cerradas donde la humedad relativa sea la medida o una de las medidas
    adoptadas para controlar la acumulación de electricidad estática se deberá realizar lo siguiente:
    a) Mantener la humedad relativa en un nivel superior a 65%;
    b) Medir la humedad relativa y registrar su valor, al menos cada doce meses y/o cuando se realicen
    modificaciones al área de trabajo que puedan afectar esta condición.
  23. c) Monitorear, en su caso, la humedad relativa de las áreas o procesos de manera continua cuando
    constituya una medida de seguridad contra peligro de incendio o explosión. El monitoreo deberá
    realizarse mediante equipos que cuenten con alarma que indique que la humedad relativa ha descendido
    a niveles inferiores al establecido en el inciso a) del presente numeral.
    El equipo que se utilice para la medición y/o monitoreo de la humedad relativa deberá contar con
    certificado de calibración vigente, en los términos que dispone la Ley Federal sobre Metrología y
    Normalización.
    7.4 En las áreas de trabajo donde la presencia de electricidad estática en el cuerpo del trabajador
    drenar a tierra las corrientes que se hayan acumulado en él.
    7.5 En las zonas donde se manejen, almacenen o transporten sustancias inflamables o explosivas,
    deberán conectarse a tierra las partes metálicas que no estén destinadas a conducir energía eléctrica y
    que no se encuentren ya inherentemente conectados a tierra, tales como tanques metálicos, cajas
    metálicas de equipos, maquinaria y tuberías.
  24. Sistema de protección contra descargas eléctricas atmosféricas
    8.1 Los centros de trabajo o áreas que se clasifiquen como riesgo de incendio alto de acuerdo con lo
    establecido por la NOM-002-STPS-2010, o las que la sustituyan, deberán instalar un sistema de
    protección contra descargas eléctricas atmosféricas, tal como el sistema de pararrayos.
    Para el diseño e instalación del sistema de protección contra descargas eléctricas atmosféricas, puede
    consultarse la Norma Mexicana NMX-J-549-ANCE-2005, o las que la sustituyan.
    En la Guía de referencia I, se presentan algunos ejemplos en los que se sugiere considerar la instalación
    de un sistema de protección contra descargas eléctricas atmosféricas.
    8.2 Para seleccionar un sistema externo de protección contra descargas eléctricas atmosféricas, ya sea
    con terminales aéreas convencionales o terminales aéreas de tecnologías alternativas, se deberán
    considerar, al menos, los factores siguientes:
    a) El arreglo general del centro de trabajo (planta, cortes y elevaciones);
    b) Las sustancias inflamables o explosivas que se almacenen, manejen o transporten en el centro de
    trabajo, en cuanto a su inflamabilidad o explosividad, y la tendencia a generar y acumular cargas
    eléctricas estáticas, por sus características fisicoquímicas y las de los contenedores y/o tuberías, así
    como la naturaleza de los procesos a que están sujetas, y las condiciones presentes del ambiente;
    c) La densidad del rayo a tierra de la región, y
    d) La zona de protección del sistema.
    8.3 El centro de trabajo deberá contar con un estudio que demuestre que el área de cobertura del
    sistema externo de protección contra descargas eléctricas atmosféricas comprende el edificio, local o
    zona de riesgo en la que se manejan las sustancias inflamables o explosivas. El estudio deberá ser
    elaborado por un ingeniero electricista o afín, y contener, al menos, lo siguiente:
    a) Tipo y características del sistema instalado;
    b) Altura de las terminales aéreas que sobresalen de cualquiera de las estructuras circundantes;
    c) Ubicación del sistema;
    d) Área de cobertura de protección con la metodología utilizada para su cálculo, y
    e) Nombre y firma de quien lo elaboró, así como número
    de cédula profesional.
    8.4 Para reducir el riesgo de choque eléctrico derivado de la circulación de la corriente de rayo en los
    conductores de bajada y en los elementos de la red de puesta a tierra del sistema externo de protección
    contra descargas eléctricas atmosféricas, se deberá adoptar lo siguiente:
    a) Instalar un arreglo del sistema de puesta a tierra y proveer una superficie de alta resistividad en la
    zona de tránsito de trabajadores, tal como grava triturada de 0.10 metros de espesor como mínimo,
    entre el terreno natural y los elementos del sistema de puesta a tierra;
    b) Proveer una canalización no metálica con resistencia a la intemperie sobre la superficie del
    conductor de bajada con el objeto de reducir la posibilidad de contacto accidental o incidental de los
    trabajadores;
    c) Colocar en la canalización avisos de precaución que indiquen el «PELIGRO: EVENTUAL
    CORRIENTE DE RAYO», conforme a lo dispuesto por la NOM-026-STPS-2008, o las que la
    sustituyan;
    d) Unir eléctricamente al sistema de puesta a tierra (por debajo del nivel de piso) todos los elementos
    metálicos y acero de refuerzo de la estructura a proteger, mediante electrodos de puesta a tierra
    horizontales colocados a una profundidad mínima de 0.60 metros, y
    e) Instalar el conductor de bajada de tal forma que su recorrido sea lo más corto posible y se eviten
    cruces con instalaciones eléctricas.
    8.5 Los trabajadores que realicen actividades en lugares en los que exista exposición a la incidencia de
    descargas atmosféricas, y no estén protegidos contra este riesgo, tales como azoteas de edificios que
    sobresalen en altura con respecto a otras estructuras contiguas, postes o torres de alumbrado o
    cableado, plataformas elevadas, antenas, entre otros, deberán suspender la actividad tan pronto se
    aproxime una tormenta eléctrica.
    8.6 La red de puesta a tierra de los sistemas de pararrayos deberá interconectarse con otras redes de
    puesta a tierra, tales como las de motores, subestaciones o sistema eléctrico en general.
    8.7 Los electrodos de la red de puesta a tierra de los sistemas de pararrayos deberán permitir su
    desconexión cuando se realice la medición a que se refiere el Capítulo 9 de esta Norma. Para ello, los
    electrodos deberán contar con medios que permitan su desconexión y que eviten falsos contactos.
    8.8 Queda prohibido utilizar pararrayos que estén fabricados o funcionen a base de materiales
    radiactivos.
  25. Medición de la resistencia a tierra de la red de puesta a tierra
    9.1 La medición de la resistencia a tierra de la red de puesta a tierra se deberá realizar aplicando el
    método de caída de tensión, de conformidad con lo que prevé el numeral 9.4 de la presente Norma.
    Esta medición deberá efectuarse tomando en consideración la condición más desfavorable en cuanto al
    grado de humedad del terreno en el que se ha instalado la red de puesta a tierra.
    9.2 Para realizar la medición de la resistencia a tierra de la red de puesta a tierra se deberá contar con
    los instrumentos siguientes:
    a) Equipo de medición de resistencia de tierra con las características siguientes:
    1) Intervalo de frecuencia de 90 Hz a 200 Hz o mayor, y
    2) Con capacidad de proveer corriente con valores de al menos 0.1 mA;
    b) Accesorios provistos por el fabricante del equipo de medición o, en caso de no contar con
    accesorios para el equipo de medición, utilizar cable o cordón aislado de cobre de forro apropiado a las
    condiciones de uso con una designación de uso más común de 2.08 mm2 (14 AWG) o 1.307 mm2 (16
    AWG), con accesorios en sus extremos para la correcta conexión al equipo y electrodos auxiliares con
    una longitud mínima de 50 centímetros y un diámetro mínimo de 13 milímetros de alguno de los
    materiales siguientes: acero inoxidable, acero con recubrimiento de cobre o acero galvanizado
    c) Óhmetro o medidor de resistencia a tierra para comprobar la continuidad de las conexiones a tierra,
    con una resolución de al menos 1 ohm;
    d) Voltímetro con resolución de al menos 1 volt, y
    e) Flexómetro o instrumento similar de medición de longitud.
    9.3 El óhmetro o medidor de resistencia a tierra y el voltímetro deberán contar con certificado de
    calibración vigente, en los términos de lo determinado por la Ley Federal sobre Metrología y
    Normalización.
    9.4 La medición de la resistencia a tierra de la red de puesta a tierra se deberá realizar conforme a lo
    siguiente:
    a) Verificar que el electrodo bajo prueba (que corresponde a la red de puesta a tierra) esté
    desconectado de la red de puesta a tierra, considerando lo siguiente:
    1) Realizar la desconexión de la red de puesta a tierra, con los equipos eléctricos desenergizados, y
    2) Efectuar la medición de la resistencia a tierra desconectando cada electrodo de forma individual,
    cuando ésta se realice en condiciones de operación normal, a fin de no desproteger a los trabajadores;
    b) Ajustar a cero la aguja del instrumento de medición analógico o verificar que la fuente de poder
    del equipo digital tenga suficiente energía para realizar el conjunto de mediciones;
    c) Aplicar el método de caída de tensión de la manera siguiente:
    1) Hacer circular una corriente entre dos electrodos: uno llamado C1 (que corresponde a la red de
    puesta a tierra) y un electrodo auxiliar denominado C2, mismo que se introduce al terreno a una
    distancia mínima de 20 metros de C1. Para realizar la primera medición se introduce en el terreno otro
    electrodo auxiliar llamado P1, a un metro de distancia de C1, entre el electrodo bajo prueba C1 y el
    electrodo auxiliar C2;
    2) Desplazar el electrodo auxiliar P1 de manera lineal a 3 metros de la primera medición y en
    dirección al electrodo auxiliar C2 para realizar la segunda medición, y
    3) Realizar las mediciones siguientes desplazando el electrodo auxiliar P1 cada 3 metros hasta
    complementar 19 metros. En la Figura 1 se muestra la colocación de los electrodos de la red de puesta a
    tierra, y auxiliares;
    d) Registrar los valores obtenidos de las mediciones;
    e) Elaborar una gráfica con base en los valores registrados, similar a la que se ilustra en la parte
    inferior de la Figura 1 siguiente;
    D1 Distancia entre el electrodo de la red de puesta a tierra C1 y el electrodo auxiliar P1.
    DT Distancia entre el electrodo de la red de puesta a tierra C1 y el electrodo auxiliar C2.
    Figura 1 Posición de electrodos y gráfica de valores de resistencia eléctrica vs. distancia
    f) Obtener el valor de la resistencia a tierra de la red de puesta a tierra de la intersección del eje de
    resistencia con la parte paralela de la curva al eje de las distancias;
    g) Repetir las mediciones alejando el electrodo C2 del electrodo C1, cuando la curva obtenida no
    presente un tramo paralelo, hasta obtener valores paralelos al eje de las distancias, y
    h) Verificar que los valores de la resistencia a tierra, de la red de puesta a tierra que se obtengan en
    esta prueba, sean menores o iguales a 10 ohms para el (los) electrodo(s) del sistema de pararrayos, y/o
    tener un valor menor o igual a 25 ohms para la resistencia a tierra de la red de puesta a tierra.
    9.5 El resultado de las mediciones tendrá que registrarse, dicho registro deberá contener, como mínimo,
    lo siguiente:
    a) Los datos del centro de trabajo:
    1) Nombre o razón social del centro de trabajo;
    2) Domicilio del centro de trabajo;
    3) Fecha de realización de la medición, y
    4) Nombre y firma de la persona que realizó la medición;
    b) Los datos de los instrumentos de medición:
    1) Nombre genérico del instrumento utilizado;
    2) Características del equipo de medición utilizado (modelo, número de serie, intervalos de medición,
    precisión, exactitud, etc.), y
    3) Copia del certificado de calibración vigente del instrumento utilizado;
    c) Los valores de las mediciones:
    1) Valores de resistencia a tierra de la red de puesta a tierra y/o de la resistencia a tierra del (los)
    electrodo(s) del sistema de pararrayos, y
    2) Indicación de si existe continuidad eléctrica de los puntos de conexión del sistema;
    d) El croquis en el que se muestre los puntos de medición del sistema de puesta a tierra y, en su caso,
    del (los) electrodo(s)del sistema pararrayos, y
    e) Las características del sistema de pararrayos utilizado, en su caso, con al menos lo siguiente:
    1) Tipo de sistema de pararrayos;
    2) Altura de las terminales aéreas;
    3) Ubicación, y
    4) Área de cobertura de protección.
  26. Capacitación y adiestramiento
    10.1 A los trabajadores involucrados en actividades en las que se genere o acumule electricidad
    estática, en la instalación, revisión de sistemas de puesta a tierra y sistemas de pararrayos, así como en
    la determinación de la resistencia a tierra y continuidad de las redes, se les deberá proporcionar
    capacitación y adiestramiento para llevar a cabo estas actividades y prevenir los riesgos derivados de
    estas actividades, la cual comprenderá, al menos, lo siguiente:
    a) Los fundamentos técnicos sobre la generación y acumulación de cargas eléctricas estáticas;
    b) Los procesos en los que ocurre la generación y acumulación de cargas eléctricas estáticas, con
    énfasis en los que se llevan a cabo en su centro de trabajo, y los mecanismos físicos por los cuales se da
    en cada caso este fenómeno;
    c) Los materiales sólidos y fluidos, aislantes, semiconductores y conductores, susceptibles de
    cargarse electrostáticamente;
    d) Los riesgos ocasionados por la electricidad estática, los métodos disponibles para su control,
    disipación y descarga;
    e) Los riesgos derivados de descargas eléctricas atmosféricas y las medidas de seguridad para
    evitarlos;
    f) Las medidas de seguridad que señala esta
    Norma para prevenir los riesgos por generación y acumulación de electricidad estática;
    g) Las condiciones de seguridad implementadas en el centro de trabajo, de manera adicional a lo
    dispuesto por la presente Norma;
    h) Los procedimientos, en su caso, para llevar a cabo la instalación, revisión de sistemas de puesta a
    tierra y sistemas de pararrayos, así como para la determinación de la resistencia a tierra y continuidad
    de las redes, e
    i) El uso adecuado del equipo de protección personal que se le suministre para el desarrollo de sus
    actividades, de conformidad con lo dispuesto por la NOM-017-STPS-2008, o las que la sustituyan.
    10.2 La capacitación y adiestramiento que se proporcione a los trabajadores deberá reforzarse por lo
    menos cada dos años.
    10.3 Los centros de trabajo deberán llevar el registro de la capacitación y adiestramiento que
    proporcionen a los trabajadores, el cual deberá contener, al menos, lo siguiente:
    a) El nombre y puesto de los trabajadores a los que se les proporcionó;
    b) La fecha en que se proporcionó la capacitación y el adiestramiento;
    c) Los temas impartidos
    d) El nombre del instructor y, en su caso, número de registro como agente capacitador ante la
    Secretaría del Trabajo y Previsión Social.
  27. Unidades de verificación y laboratorios de prueba
    11.1 El patrón tendrá la opción de contratar una unidad de verificación y/o un laboratorio de pruebas,
    acreditados y aprobados en los términos de lo que establece la Ley Federal sobre Metrología y
    Normalización y su Reglamento.
    11.2 Las unidades de verificación contratadas a petición de parte deberán verificar el grado de
    cumplimiento con esta Norma, conforme a lo previsto por el procedimiento para la evaluación de la
    conformidad del Capítulo 12 de la presente Norma, y en su caso emitir un dictamen de cumplimiento,
    el cual habrá de contener:
    a) Datos del centro de trabajo verificado:
    1) Nombre, denominación o razón social;
    2) Registro Federal de Contribuyentes;
    3) Domicilio completo;
    4) Teléfono, y
    5) Actividad principal;
    b) Datos del organismo privado:
    1) Nombre, denominación o razón social;
    2) Número de acreditación;
    3) Número de aprobación otorgado por la Secretaría del Trabajo y Previsión Social, y
    4) Domicilio completo, y
    c) Datos del dictamen:
    1) Clave de la norma;
    2) Nombre del verificador evaluado y aprobado;
    3) Servicios prestados: elaboración, ejecución y validación, en el caso de dictámenes con reporte de
    servicios;
    4) Fecha de verificación;
    5) Número de dictamen;
    6) Vigencia del dictamen;
    7) Lugar de emisión del dictamen, y
    8) Fecha de emisión del dictamen.
    11.3 Los laboratorios de prueba sólo podrán evaluar lo que determinan los numerales 5.3 y 7.2 inciso
    c), el Capítulo 9, y en su caso, lo señalado por el numeral 7.3 de esta Norma.
    11.4 Los laboratorios de prueba deberán emitir un informe de resultados que incluya el registro, de
    acuerdo con lo que dispone el numeral 9.5 de la presente Norma y, en su caso, el resultado de la
    medición de la humedad relativa. El informe de resultados deberá contener:
    a) Datos del centro de trabajo evaluado:
    1) Nombre, denominación o razón social;
    2) Registro Federal de Contribuyentes;
    3) Domicilio completo;
    4) Teléfono, y
    5) Actividad principal;
    ventas1@simmexico.com
    www.simmexico.com.mx
    (614) 3-06-20-56 ó 3-35-03-27
    b) Datos del organismo privado:
    1) Denominación o razón social;
    2) Número de acreditación;
    3) Número de aprobación otorgado por la Secretaría del Trabajo y Previsión Social, y
    4) Domicilio completo, y
    c) Datos del informe de resultados:
    1) Clave de la norma, el procedimiento para la medición de la resistencia a tierra del (los) electrodo(s)
    del sistema de pararrayos y de la red de puesta a tierra, de conformidad con lo establecido en los
    numerales 9.1 y 9.4 de esta Norma, la comprobación de la continuidad en los puntos de conexión a
    tierra y, en su caso, la medición y/o monitoreo de la humedad relativa;
    2) Nombre del signatario evaluado y aprobado;
    3) Equipo utilizado y su número de serie, con base en lo que prevén los numerales 9.2 y 9.3 de la
    presente Norma;
    4) Fecha en que se realizó la medición de la resistencia a tierra del (los) electrodo(s) del sistema de
    pararrayos y de la red de puesta a tierra, y comprobó la continuidad en los puntos de conexión a tierra
    y, en su caso, la medición y/o monitoreo de la humedad relativa;
    5) Los resultados de las mediciones conforme a lo determinado por el numeral 9.5 de esta Norma;
    6) Número del informe de resultados;
    7) Vigencia del informe de resultados;
    8) Lugar de emisión del informe de resultados, y
    9) Fecha de emisión del informe de resultados.
    11.5 La vigencia del dictamen de verificación y del informe de resultados cuando éstos sean favorables,
    será de un año, siempre y cuando no sean modificadas las condiciones que sirvieron para su emisión.
    11.6 El directorio de las unidades de verificación y laboratorios de prueba que están aprobados por la
    dependencia, se puede consultar la página de la Secretaría del Trabajo y Previsión Social, vía Internet,
    en la dirección electrónica: http://organismosprivados.stps.gob.mx/organismosprivados/index.html.
  28. Procedimiento para la Evaluación de la Conformidad
    12.1 El procedimiento para la evaluación de la conformidad aplica tanto a las visitas de inspección
    desarrolladas por la autoridad laboral, como a las visitas de verificación que realicen las unidades de
    verificación.
    12.2 El informe de resultados y el dictamen de verificación vigente, en su caso, deberán estar a
    disposición de la autoridad laboral cuando ésta lo solicite.
    12.3 Los aspectos a verificar durante la evaluación de la conformidad de la presente Norma se
    realizarán, según aplique, mediante la constatación física, revisión documental, registros o entrevistas,
    de conformidad con lo siguiente:
    12.4 Para la selección de trabajadores por entrevistar, con el propósito de constatar el cumplimiento de
    las disposiciones que dispone el presente procedimiento para la evaluación de la conformidad, se
    aplicará el criterio muestral contenido en la Tabla 2 siguiente:
    Tabla 2
    Muestreo por selección aleatoria
    Número total de trabajadores
    Número de trabajadores por entrevistar
    1-15
    1
    16-50
    2
    51-105
    3
    Más de 105
    1 por cada 35 trabajadores hasta un máximo de 15
    12.5 Las evidencias de tipo documental o los registros a que alude esta Norma podrán exhibirse de
    manera impresa o en medios magnéticos, y se deberán conservar al menos durante un año.
  29. Vigilancia
    La vigilancia del cumplimiento de la presente Norma Oficial Mexicana corresponde a la Secretaría del
    Trabajo y Previsión Social.
    TRANSITORIOS
    PRIMERO. La presente Norma Oficial Mexicana entrará en vigor a los seis meses siguientes a su
    publicación en el Diario Oficial de la Federación.
    SEGUNDO. Durante el lapso señalado en el artículo anterior, los patrones cumplirán con la Norma
    Oficial Mexicana NOM-022-STPS-2008, Electricidad estática en los centros de trabajo – Condiciones
    de seguridad, o bien realizarán las adaptaciones para observar las disposiciones de esta Norma Oficial
    Mexicana y, en este último caso, la autoridad laboral proporcionará, previa solicitud por escrito de parte
    de los patrones interesados, asesoría y asistencia técnica en los términos que establece el Reglamento
    Federal de Inspección Federal del Trabajo y Aplicación de Sanciones, a efecto de instrumentar su
    cumplimiento, sin que los patrones se hagan acreedores a sanciones por el incumplimiento de la Norma
    en vigor.
    TERCERO. A partir de la fecha en que entre en vigor la presente Norma quedará sin efectos la Norma
    Oficial Mexicana NOM-022-STPS-2008, Electricidad estática en los centros de trabajo – Condiciones
    de seguridad, publicada en el Diario Oficial de la Federación el 7 de noviembre de 2008.
    Ciudad de México, a los diecisiete días del mes de marzo de dos mil dieciséis.- El Secretario del
    Trabajo y Previsión Social, Jesús Alfonso Navarrete Prida.- Rúbrica.