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

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