BS EN 62305:2006BS EN 62305:2006

Protection against lightningProtection against lightning

An OverviewAn OverviewAn OverviewAn Overview

Sanjeev Talwar

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BS EN 62305:2006 is the first ever British Li ht i P t ti St d d t b il d bLightning Protection Standard to be compiled by experts from all over the world

Very ‘wordy’ yet comprehensive document

Following presentation is based on our interpretation of BS EN 62305:2006interpretation of BS EN 62305:2006

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BS EN 62305 parts 1 4BS EN 62305 parts 1-4

• Published September 2006

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Now lets review BS EN 62305 inNow lets review BS EN 62305 in a little more detail

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Peak currents are developedPeak currents are developed in a lightning strike……..

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b t t i i…but, event is over in millionths of a secondmillionths of a second (typically 50s)( yp y )

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Lightning flash - adjacent air inLightning flash adjacent air in ionized channel of strike

--approx 30000approx 30000°°CC

-- explosive expansionexplosive expansion-- explosive expansion explosive expansion of surrounding airof surrounding air

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St ik d lStrike damage examples

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St ik d lStrike damage examples

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BS EN 62305

BS EN 62305 (4 documents)I t d d i S t b 2006Introduced in September 2006

BS6651 withdrawal date isBS6651 withdrawal date is August 31st 2008

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Key changes: BS 6651 and BS EN 62305

BS 6651 BS EN 62305

Simple Risk Assessment (structural damage)

Comprehensive Risk Management Calculation based on Four types ofdamage) Calculation based on Four types of

risk (R1-R4)

T l l f li ht i t ti F l l f Li ht i P t tiTwo levels of lightning protection –ordinary and high risk

Four levels of Lightning Protection System (LPS)

I-IV

Transient Over-voltage (Surge) protection in Appendix C

(informative)

Transient Over-voltage / current (Surge) protection incorporated in main standard detailed in BS EN(informative) main standard – detailed in BS EN

62305-4

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BS EN 62305 - 4 parts

BS EN 62305-1 General Principles

BS EN 62305-2 Risk Management

BS EN 62305-3 Physical damage & life hazardhazard

BS EN 62305-4 Electrical & electronicBS EN 62305 4 Electrical & electronic systems

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BS EN 62305-1 (Part 1)

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BS EN 62305-1 (Part 1)

General Principles of Lightning protection

Leads-in/introduction to other partsLeads in/introduction to other parts

Explains storyline how to design an LPSin accordance with accompanying parts ofp y g pthis standard

1862305-1

Scope – BS EN 62305 - 1 pProvides general principles for protection against lightning of:• structures, their installations, contents and persons• services connected to a structure

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BS EN 62305 1BS EN 62305-1LPL (Lightning Protection Level)

- number related to a set of lightning current parameters, which allows relevant protection measures to be applied i l di th i f th lli hincluding the size of the rolling sphere

LPL Maximum (kA) Minimum (kA)LPL Maximum (kA) Minimum (kA)

I 200 3

II 150 5

III 100 10III 100 10

IV 100 16

2062305-1

In order to evaluate whether lightning

protection is required, a risk assessment

needs to be carried outneeds to be carried out

(BS EN 62305-2)

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BS EN 62305-2 (Part 2)( )

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BS EN 62305 2 (Pa t 2)BS EN 62305-2 (Part 2)

Risk ManagementRisk ManagementComplex document embracing many more factors than the BS6651 risk assessment New approach to Riskthe BS6651 risk assessment. New approach to Risk assessment. Looks at Risk in a far broader sense.

By working through series of formulae the processBy working through series of formulae the process allows the user to decide on what protection is required to reduce the actual Risk (R) below it’s corresponding tolerable level (RT)

The ultimate protection may be the installation of anThe ultimate protection may be the installation of an LPS system, transient (LEMP) protection or even an automatic fire fighting systemg g y

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62305-2

Following primary risks (Rn) relate to g p y ( n)corresponding types of loss (L)

R1 – risk of loss of human life

R2 – risk of loss of services to the public

R i k f l f lt l h itR3 – risk of loss of cultural heritage

R risk of loss of economic valueR4 – risk of loss of economic value

2462305-2

P t ti i t li ht i i i d ifProtection against lightning is required if

the risk Rn(whether R1 or R2 or R3) isthe risk Rn(whether R1 or R2 or R3) is

greater than the tolerable level of risk RT

ie R > Rie Rn > RT

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Tolerable risk RT (BS EN)T ( )

Type of loss RT(y-1)

Loss of human life or permanent injury R

10-5

permanent injury R1

Loss of service to public R2 10-4

Loss of cultural heritage R3 10-4

Note. y-1 means ‘in one year’

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1 Use and type of structure (Lf)2 Dimensions of structure (L x W x H in metres)3 No of service lines feeding the structure

power single/three phase overhead underground Critical Weighting- power, single/three phase, overhead, underground- telecon, how many lines, overhead, underground

4 Length of service lines (Lc)5 Location (Cd)

Critical Weighting Factors

d

6 Environment (urban, suburban, rural) (Ce)7 Service line only or with transformer (Ct)8 Special hazards (low, average, high level of panic) (hz)9 Type of surface (concrete asphalt wood etc) (r & r )9 Type of surface (concrete, asphalt, wood etc) (ra & ru)10 Any fire protection provisions? (manual extinguisher, automatic extinguishing system) (rp)11 Risk of fire (high, ordinary, low) (rf)12 Soil resistivity (ρ)y (ρ)13 Voltage withstand (Uw) of (a) power cable (b) telecom cable (KS4)14 Any spatial screening (any re-inforcing bars/stanchions within the framework of the structure? (KS1)15 - Any details of service lines? (KS3)

Screened/unscreened cable- Screened/unscreened cable- routing

16 Flash Density (Ng)

27 S1

S3

S2S2S4

Sources of damage to a structureS1 – Flashes to a structureS1 Flashes to a structure

S2 – Flashes near a structure

S3 Fl h t i t d t t tS3 – Flashes to services connected to a structure

S4 – Flashes near services connected to a structure

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R +R +R R +R +R

R +R +RA B C R +R +RU V W

RM RRM RZ

R R RR1 = RD + Ri

= (RA + RB + RC) +( A B C)(RM + RU + RV + RW + RZ)

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Each primary risk consists of numerous risk components

R1 = RA + RB + RC(1) + RM

(1) + RU + RV + RW(1) + RZ

(1)

R2 = RB + RC + RM + RV + RW + RZ

R R + RR3 = RB + RV

R4 = RA(2) + RB + RC + RM + RU + RV + RW + RZ

(1) Structures – risk of explosion or hospitals – life saving equipment( ) p p g q p

(2) Properties where animals may be lost

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Definition of numerous risk componentsDefinition of numerous risk components

Source of Damage Type of DamageXRSou ce o a age ype o a age

Flashes to the structure (S1) Injury to living beings (D1)

Flashes to the structure (S1) Physical damage caused by

AR

BRdangerous sparking inside the structure (D2)

Flashes to the structure (S1) Failure of internal systems caused by Lightning Electro Magnetic Pulse -CR

BR

g g gLEMP (D3)

Flashes near the structure (S2) Failure of internal systems caused by LEMP (D3)MR

Flashes to a service connected to the structure (S3)

Injury to living beings (D1)

Flashes to a service connected to structure (S3)

Physical damage caused by dangerous sparking inside the

UR

VR ( ) g p gstructure (D2)

Flashes to a service connected to structure (S3)

Failure of internal systems caused by LEMP (D3)WR

VR

Flashes near a service connected to structure (S4)

Failure of internal systems caused by LEMP (D3)ZR

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Generic equation for evaluating each risk component is:component is:

RX = NX . PX . LX

where

N = annual number of dangerous eventsNX = annual number of dangerous events

PX = probability of damage

LX = consequential loss (social values)

32For example RB component related to physical damage caused by dangerous sparking inside structure triggering fire or explosion

RB = ND . PB . LB

RB = (NgAd/bCd/b . 10-6) (PB) (hz.rp.rf.Lf)Where, Ad/b (collection area) = LW + 6H (L+W) + 9π(H)2

Cd/b is the Location factor, derived from the table/

PB is the probability of damage to the structure, derived from the table, depending upon the level of protection

hz is the factor increasing the loss due to physical damage, when a special hazard is present, derived from the table

rp is the factor reducing the loss due to physical damage depending on the provision taken to reduce the consequences of fire, derived from the table

rf is the factor reducing the loss due to physical damage depending on the risk of fire, derived from the table

LLf is loss due to physical damage

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Lf ( loss due to physical damage )np is the possible number of victims in case of S1

nt is the number of people occupying the structuret p p py g

tp is the expected time spent by people in the structure

ptxpn

L 8760xtnfL

87603650

200200 xfL 42.0fL

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Equivalent risk component to RB applicable to services is RV, (most important for the ME area) component related to physical damage (fire or explosion) triggered by dangerous sparking generally at entrance point of line into structuresparking generally at entrance point of line into structure due to lightning current transmitted along incoming service

R = N P LRV = NV . PV . LV

and RV = (NL + NDa)(PV)(hz.rp.rf.Lf)

where NL = Ng . Al . Cd . Ct . 10-6

and N = N A C C 10-6and NDa = Ng . Ad/a . Cd/a . Ct . 10 6

and Al = Lc – 3(Ha + Hb)6Hc – Aerial (overhead) cable

This exercise is repeated for all other all risk componentsor Al = [L c – 3(Ha + Hb)] – Buried cable

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Risk Management

Long hand calculations – laborious, time consuming,Long hand calculations laborious, time consuming, not practicable in commercial environment

Furse strike risk software – commercialFurse strike risk software commercial availablility by 30th June 2007

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BS EN 62305-3 - Physical damage to d lif h dstructures and life hazard

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BS EN 62305 3 Ph i l d tBS EN 62305-3 Physical damage to structures and life hazard

Relates directly to major part of BS6651

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62305-3

• Follows Faraday Cage principle

4 l f l LP• 4 classes of structural LP

2 types of earthing arrangements• 2 types of earthing arrangements

• focus on importance of equipotential bonding• focus on importance of equipotential bonding

• encourages use of natural metalwork

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Class Mesh Size ( )

DC spacing (m)

Rolling Sphere (m)(m x m) (m) Sphere (m)

I 5 x 5 10 20

II 10 x 10 10 30

III 15 x 15 15 45

IV 20 20 20 60IV 20 x 20 20 60

Each class has its own mesh size, dc spacing and relevant radius of rolling sphere

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Minimum Lightning Current ParametersMinimum Lightning Current Parameters

The minimum values of Lightning current haveThe minimum values of Lightning current have been used to derive the Rolling Sphere radius for each Lightning Protection Level Thefor each Lightning Protection Level. The relationship between the minimum peak current and the striking distance (or in othercurrent and the striking distance (or in other words the Rolling Sphere Radius and is expressed as:expressed as:

65010 I 65.010 Ixr

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Ai T i ti S t62305-3

Air Termination System

3 basic protective methods for determining position of air termination system

• Rolling sphere method

• Protective angle method

• Mesh method

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Mesh Method

Suitable for majority of the surfaces provided:

Mesh Method

• conductors are positioned at roof edges and p goverhangs, and on roof ridges

• no installation should protrude above air termination system – or provide air t i l t t t thterminals to protect them

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LPZ 0A

Zone of protection

LPZ 0B

sLPS

EquipmentB

Overvoltage SPD LPZ 1 (8/20 s)LPZ 1

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LPZ 0LPZ 0A

LPS

Equipment

Lightning current SPD (10/350 )LPZ 1 (10/350 s)LPZ 1

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D C d tDown Conductors

Use of aesthetic covering (pvc, paint) overUse of aesthetic covering (pvc, paint) over

external LP conductors permitted

(BS EN 50164 2 (A1))(BS EN 50164-2 (A1))

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Aluminum roof – air termination network

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Mesh Method62305-3

Natural components (metallic roofs)

Mesh Method

Class of LPS Material Thickness(1)

t (mm)Thickness(2)

t’ (mm)

Lead - 2.0

Steel (stainless, 4 0.5

I to IVgalvanized)

Copper 5 0.5

Al i i 7 0 65Aluminium 7 0.65

Zinc - 0.7NOTE 1 hi k h i i iNOTE 1: thickness t prevents puncture, hot spot or ignition.NOTE 2: thickness t’ only for metal sheets if it is not important to prevent puncture, hot spot or ignition problems.

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•Spacing Between Fixing clips : 500mm on a•Spacing Between Fixing clips : 500mm on a vertical surface at a height of 20m upwards. 1000mm on vertical surface upto 20m from the1000mm on vertical surface upto 20m from the ground and on all Horizontal surfaces

• Ring Conductor

- conductor forming loop around structure and interconnecting down conductors to gimprove lightning current distribution down themthem.

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Ri C d t S i62305-3

Ring Conductor SpacingDepending on the level of protection, the radius of the rolling sphere is decidedsphere is decided.

Assume LPL I1st Ri C d t t 20 h i ht•1st Ring Conductor at 20 m height

•Spacing of 20 meters (5 floors) between 20m to 120m height

•Spacing of 10 meters (3 floors) between 120m to 400m height

•Spacing of 5 meters (each floor) from 400m height onwards

•If the structure is >120m in height, then apply ring conductor onIf the structure is >120m in height, then apply ring conductor on each floor for the top 20% and then follow the above rule

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Down Conductors

Where it is not possible to install d.c’s down a particular side due to practical/architectural

b l d ’restraints – compensate by placing more d.c’s at closer spacings on other accessible sides

d.c centres should not be less than one third of its relevant distance

eg Class III LPS equates to 15m spacing

Thus minimum d c spacing (15/3) 5mThus minimum d.c spacing (15/3) = 5m

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Natural Components62305-3

Encourages use of natural fortuitous metalwork

Natural Components

Encourages use of natural fortuitous metalwork present (ie rebars, etc)

Still eq i es elect ical contin it ma im mStill requires electrical continuity - maximum overall resistance of 0.2 ohm

R i f i b i li h iReinforcing bars carrying lightning currents should be welded, clamped with suitable connection components or overlapped minimumconnection components or overlapped minimum of 20 times rebar diameter

Rebars used for EMC purposes wire lashing isRebars used for EMC purposes – wire lashing is deemed suitable

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Earth Termination System

a) Type A arrangementa) Type A arrangement

rods or horizontal conductor electrodes

b) Type B arrangementb) Type B arrangement

ring conductor or foundation earth electrode

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Type A Arrangement62305-3

Type A Arrangement

Total number of rods/earth electrodes shouldTotal number of rods/earth electrodes should not be less than two

OR

Minimum length of earth rod shall be 2.4m

However, please use the formula to find out the actual number of earth rods required beforeactual number of earth rods required before deciding on installation

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Lightning Protection Components

BS EN 62305 requires that all connection

components used in an LPS meet the relevant

requirements of the BS EN 50164 series ofrequirements of the BS EN 50164 series of

Standards.

Testing done by BSEN accredited laboratory only

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BS EN 50164-1

E l f b f d ft t tiExamples of before and after testing

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Lightning Protection Components

All Furse components meet the requirements of

BS EN 50164-1 and BS EN 50164-2BS EN 50164 1 and BS EN 50164 2

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Maintenance and Inspection of LPSBS6651 – inspect/test annually (11 months)

Maximum period between inspections (62305-3)

Protection Visual Complete Critical level inspection

(year)

pinspection (year)

systems * complete i tiinspection (year)

I d II 1 2 1I and II 1 2 1

III and IV 2 4 1

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Non-conventional Air Termination Systems

Lot of technical (and commercial) debate raged over the yearsy

Topic discussed extensively within technical

D i i t i ith i f ti t i d

p yworking groups

Decision to remain with information contained within this standard

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Non-conventional Air Termination Systems

Annex A (normative) states unequivocally that f i ff d d b i i l h ll

Non conventional Air Termination Systems

zone of protection afforded by air terminal shall be determined by “real physical dimensions” of that terminalthat terminal

5m tall Class II LPS 64° (10.5m radius) f t tizone of protection

BS EN 62305 remain in force until at least 2010

No other standard being contemplated to run in parallelparallel

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BS EN 62305 4BS EN 62305 -4

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BS EN 62305 - 4

Electrical and electronic systems within structures

BS EN 62305 4

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• Electronic systems now part of our everyday life –totall dependent on thei smooth efficient nningtotally dependent on their smooth efficient running

• Any malfunctions, loss of data etc – disastrous effects on companies

• Part 4 recognizes vital importance of protecting electrical/electronic systems housed within structureselectrical/electronic systems housed within structures – integral part of BS EN 62305

6762305-4

Electrical and electronic systems within structures

Basic protection measures in an LPMS

Electrical and electronic systems within structures

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• earthing and bonding• earthing and bonding

ti hi ldi d li ti• magnetic shielding and line routing

• surge protective device set

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S t ti d i t (SPD t)62305-4

Surge protective device set (SPD set)

• protection of internal systems against• protection of internal systems against surges may require an SPD set consisting of a coordinated set of SPD’sof a coordinated set of SPD s

SPD shall be suitably located at :• SPD shall be suitably located at :

- Main distribution board (service entrance)( )

- Sub distribution board

- Terminal equipment

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BS EN 62305 4 P t ti f l t i t• BS EN 62305-4 Protection of electronic systems

-LPMS (LEMP Protection Measures System)

- complete system of protection measures for internal systems against LEMP.

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LPZ0A

RA

LPZ1

LPZ2LPZ0B

• LPZ (Lightning Protection Zone)( g g )- zone (area) where lightning electromagnetic environment is defined

0A Full current, full magnetic field, 0B Partial/induced current full magnetic field

1 Limited induced current damped magnetic field

2 Limited induced current, further damped magnetic field

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Coordinated SPDs

Series of SPDs installed in structure – from heavy duty lightning current Type I SPD atheavy duty lightning current Type I SPD at service entrance, through to overvoltage SPD protecting terminal equipmentprotecting terminal equipment

E h SPD h ld l t h thEach SPD should complement each other such that LEMP effects are completely

llifi dnullified

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All above information is merely an insight into new standard and requires a lot more in depth reviewq p

All topics discussed today are included and expanded upon in our Guide to BS EN 62305:2006p p

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ANY QUESTIONS ?ANY QUESTIONS ?

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This concludes the presentation on p

BS EN 62305:2006 An Overview