Wind energy generation systems - Part 24: Lightning protection

IEC 61400-24:2019 applies to lightning protection of wind turbine generators and wind power systems. Refer to guidelines for small wind turbines in annex.
This document defines the lightning environment for wind turbines and risk assessment for wind turbines in that environment. It defines requirements for protection of blades, other structural components and electrical and control systems against both direct and indirect effects of lightning. Test methods to validate compliance are included.
Guidance on the use of applicable lightning protection, industrial electrical and EMC standards including earthing is provided.
This second edition cancels and replaces the first edition, published in 2010. This edition includes the following significant technical changes with respect to the previous edition:
a) it is restructured with a main normative part, while informative information is placed in annexes.

Systèmes de génération d’énergie éolienne - Partie 24: Protection contre la foudre

l’IEC 61400-24:2019 s’applique à la protection des aérogénérateurs et des parcs éoliens contre la foudre. Se reporter à l’Annexe M pour les lignes directrices applicables aux éoliennes de petite taille.Le présent document définit l’environnement de foudre applicable aux éoliennes et l’appréciation du risque pour ces mêmes éoliennes dans cet environnement. Il définit les exigences concernant la protection des pales, des autres composants structurels, ainsi que des réseaux de puissance et de commande contre les effets directs et indirects de la foudre. Les méthodes d’essai pour validation de la conformité sont incluses dans le présent document.Des recommandations relatives à l’utilisation des normes applicables en matière de protection contre la foudre, ainsi que des normes électriques industrielles et de CEM, y compris la mise à la terre sont fournies.
Cette deuxième édition annule et remplace la première édition parue en 2010. Cette édition inclut les modifications techniques majeures suivantes par rapport à l'édition précédente:
a) sa restructuration comprend une partie normative principale, les informations informatives étant intégrées dans des annexes.

General Information

Status
Published
Publication Date
02-Jul-2019
Current Stage
PPUB - Publication issued
Completion Date
03-Jul-2019
Ref Project

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IEC 61400-24
Edition 2.0 2019-07
INTERNATIONAL
STANDARD
colour
inside
Wind energy generation systems –
Part 24: Lightning protection
IEC 61400-24:2019-07(en)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
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All rights reserved. Unless otherwise specified, no part of this publication may be reproduced or utilized in any form

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---------------------- Page: 2 ----------------------
IEC 61400-24
Edition 2.0 2019-07
INTERNATIONAL
STANDARD
colour
inside
Wind energy generation systems –
Part 24: Lightning protection
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
ICS 27.180 ISBN 978-2-8322-6599-4

Warning! Make sure that you obtained this publication from an authorized distributor.

® Registered trademark of the International Electrotechnical Commission
---------------------- Page: 3 ----------------------
– 2 – IEC 61400-24:2019 © IEC 2019
CONTENTS

FOREWORD ......................................................................................................................... 11

1 Scope ............................................................................................................................ 13

2 Normative references .................................................................................................... 13

3 Terms and definitions .................................................................................................... 15

4 Symbols and units ......................................................................................................... 21

5 Abbreviated terms ......................................................................................................... 24

6 Lightning environment for wind turbine .......................................................................... 25

6.1 General ................................................................................................................. 25

6.2 Lightning current parameters and lightning protection levels (LPL) ........................ 25

7 Lightning exposure assessment ..................................................................................... 26

7.1 General ................................................................................................................. 26

7.2 Assessing the frequency of lightning affecting a single wind turbine or a

group of wind turbines ........................................................................................... 28

7.2.1 Categorization of lightning events .................................................................. 28

7.2.2 Estimation of average number of lightning flashes to a single or a group

of wind turbines ............................................................................................. 28

7.2.3 Estimation of average annual number of lightning flashes near the wind

turbine (N ) .................................................................................................. 31

7.2.4 Estimation of average annual number of lightning flashes to the service

lines connecting the wind turbines (N ) ......................................................... 32

7.2.5 Estimation of average annual number of lightning flashes near the

service lines connecting the wind turbine (N ) ................................................ 32

7.3 Assessing the risk of damage ............................................................................... 33

7.3.1 Basic equation ............................................................................................... 33

7.3.2 Assessment of risk components due to flashes to the wind turbine (S1) ......... 34

7.3.3 Assessment of the risk component due to flashes near the wind turbine

(S2) ............................................................................................................... 34

7.3.4 Assessment of risk components due to flashes to a service line

connected to the wind turbine (S3) ................................................................ 35

7.3.5 Assessment of risk component due to flashes near a service line

connected to the wind turbine (S4) ................................................................ 35

8 Lightning protection of subcomponents .......................................................................... 36

8.1 General ................................................................................................................. 36

8.1.1 Lightning protection level (LPL) ..................................................................... 36

8.1.2 Lightning protection zones (LPZ) ................................................................... 37

8.2 Blades .................................................................................................................. 37

8.2.1 General ......................................................................................................... 37

8.2.2 Requirements ................................................................................................ 37

8.2.3 Verification .................................................................................................... 38

8.2.4 Protection design considerations ................................................................... 38

8.2.5 Test methods ................................................................................................. 41

8.3 Nacelle and other structural components .............................................................. 42

8.3.1 General ......................................................................................................... 42

8.3.2 Hub ............................................................................................................... 42

8.3.3 Spinner .......................................................................................................... 42

8.3.4 Nacelle .......................................................................................................... 43

8.3.5 Tower ............................................................................................................ 43

8.3.6 Verification methods ...................................................................................... 44

---------------------- Page: 4 ----------------------
IEC 61400-24:2019 © IEC 2019 – 3 –

8.4 Mechanical drive train and yaw system ................................................................. 44

8.4.1 General ......................................................................................................... 44

8.4.2 Bearings ........................................................................................................ 44

8.4.3 Hydraulic systems ......................................................................................... 45

8.4.4 Spark gaps and sliding contacts .................................................................... 46

8.4.5 Verification .................................................................................................... 46

8.5 Electrical low-voltage systems and electronic systems and installations ................ 46

8.5.1 General ......................................................................................................... 46

8.5.2 Equipotential bonding within the wind turbine ................................................ 50

8.5.3 LEMP protection and immunity levels ............................................................ 51

8.5.4 Shielding and line routing .............................................................................. 52

8.5.5 SPD protection .............................................................................................. 53

8.5.6 Testing methods for system immunity tests .................................................... 57

8.6 Electrical high-voltage (HV) power systems .......................................................... 57

9 Earthing of wind turbines ............................................................................................... 59

9.1 General ................................................................................................................. 59

9.1.1 Purpose and scope ........................................................................................ 59

9.1.2 Basic requirements ........................................................................................ 59

9.1.3 Earth electrode arrangements ........................................................................ 59

9.1.4 Earthing system impedance ........................................................................... 60

9.2 Equipotential bonding ........................................................................................... 60

9.2.1 General ......................................................................................................... 60

9.2.2 Lightning equipotential bonding for metal installations ................................... 60

9.3 Structural components .......................................................................................... 61

9.3.1 General ......................................................................................................... 61

9.3.2 Metal tubular type tower ................................................................................ 61

9.3.3 Metal reinforced concrete towers ................................................................... 61

9.3.4 Lattice tower .................................................................................................. 61

9.3.5 Systems inside the tower ............................................................................... 62

9.3.6 Concrete foundation ...................................................................................... 62

9.3.7 Rocky area foundation ................................................................................... 62

9.3.8 Metal mono-pile foundation ............................................................................ 63

9.3.9 Offshore foundation ....................................................................................... 63

9.4 Electrode shape dimensions ................................................................................. 63

9.5 Execution and maintenance of the earthing system ............................................... 64

10 Personal safety .............................................................................................................. 64

11 Documentation of lightning protection system ................................................................ 66

11.1 General ................................................................................................................. 66

11.2 Documentation necessary during assessment for design evaluation...................... 66

11.2.1 General ......................................................................................................... 66

11.2.2 General documentation .................................................................................. 66

11.2.3 Documentation for rotor blades ...................................................................... 66

11.2.4 Documentation of mechanical systems .......................................................... 67

11.2.5 Documentation of electrical and electronic systems ....................................... 67

11.2.6 Documentation of earthing and bonding systems ........................................... 67

11.2.7 Documentation of nacelle cover, hub and tower lightning protection

systems ......................................................................................................... 67

11.3 Site-specific information ........................................................................................ 68

11.4 Documentation to be provided in the manuals for LPS inspections ........................ 68

---------------------- Page: 5 ----------------------
– 4 – IEC 61400-24:2019 © IEC 2019

11.5 Manuals ................................................................................................................ 68

12 Inspection of lightning protection system ....................................................................... 68

12.1 Scope of inspection .............................................................................................. 68

12.2 Order of inspections .............................................................................................. 68

12.2.1 General ......................................................................................................... 68

12.2.2 Inspection during production of the wind turbine ............................................ 69

12.2.3 Inspection during installation of the wind turbine ............................................ 69

12.2.4 Inspection during commissioning of the wind turbine and periodic

inspection ...................................................................................................... 69

12.2.5 Inspection after dismantling or repair of main parts ........................................ 70

12.3 Maintenance ......................................................................................................... 71

Annex A (informative) The lightning phenomenon in relation to wind turbines ...................... 72

A.1 Lightning environment for wind turbines ................................................................ 72

A.1.1 General ......................................................................................................... 72

A.1.2 The properties of lightning ............................................................................. 72

A.1.3 Lightning discharge formation and electrical parameters ................................ 72

A.1.4 Cloud-to-ground flashes ................................................................................ 73

A.1.5 Upward initiated flashes................................................................................. 79

A.2 Lightning current parameters relevant to the point of strike ................................... 82

A.3 Leader current without return stroke...................................................................... 83

A.4 Lightning electromagnetic impulse, LEMP, effects ................................................. 83

Annex B (informative) Lightning exposure assessment ........................................................ 84

B.1 General ................................................................................................................. 84

B.2 Methodology to estimate the average annual flashes or strokes to the wind

turbines of a wind farm and upward lightning activity in wind turbines ................... 84

B.2.1 General ......................................................................................................... 84

B.2.2 Methodology to determine average annual flashes to turbines of a wind
farm estimation by increase of the location factor to consider upward

lightning from wind turbines ........................................................................... 84

B.2.3 Upward lightning percentage in wind farms .................................................... 88

B.3 Explanation of terms ............................................................................................. 88

B.3.1 Damage and loss ........................................................................................... 88

B.3.2 Composition of risk ........................................................................................ 90

B.3.3 Assessment of risk components ..................................................................... 90

B.3.4 Frequency of damage .................................................................................... 91

B.3.5 Assessment of probability, P , of damage ..................................................... 92

B.4 Assessing the probability of damage to the wind turbine ....................................... 93

B.4.1 Probability, P , that a lightning flash to a wind turbine will cause

dangerous touch and step voltage ................................................................. 93

B.4.2 Probability, P , that a lightning flash to the wind turbine will cause

injury to an exposed person on the structure ................................................. 94

B.4.3 Probability, P , that a lightning flash to the wind turbine will cause

physical damage ............................................................................................ 94

B.4.4 Probability, P , that a lightning flash to the wind turbine will cause

failure of internal systems .............................................................................. 96

B.4.5 Probability, P , that a lightning flash near the wind turbine will cause

failure of internal systems .............................................................................. 96

B.4.6 Probability, P , that a lightning flash to a service line will cause injury

to human beings owing to touch voltage ........................................................ 96

B.4.7 Probability, P , that a lightning flash to a service line will cause

physical damage ............................................................................................ 97

---------------------- Page: 6 ----------------------
IEC 61400-24:2019 © IEC 2019 – 5 –

B.4.8 Probability, P , that a lightning flash to a service line will cause failure

of internal systems ........................................................................................ 97

B.4.9 Probability, P , that a lightning flash near an incoming service line will

cause failure of internal systems .................................................................... 98

B.4.10 Probability P that a person will be in a dangerous place .............................. 99

B.4.11 Probability P that equipment will be exposed to damaging event .................. 99

B.5 Assessing the amount of loss L in a wind turbine ................................................ 99

B.5.1 General ......................................................................................................... 99

B.5.2 Mean relative loss per dangerous event ......................................................... 99

Annex C (informative) Protection methods for blades ......................................................... 101

C.1 General ............................................................................................................... 101

C.1.1 Types of blades and types of protection methods for blades ........................ 101

C.1.2 Blade damage mechanism ........................................................................... 102

C.2 Protection methods ............................................................................................. 103

C.2.1 General ....................................................................................................... 103

C.2.2 Lightning air-termination systems on the blade surface or embedded in

the surface .................................................................................................. 104

C.2.3 Adhesive metallic tapes and segmented diverter strips ................................ 104

C.2.4 Internal down conductor systems ................................................................. 105

C.2.5 Conducting surface materials ....................................................................... 105

C.3 CFRP structural components .............................................................................. 106

C.4 Particular concerns with conducting components ................................................ 107

C.5 Interception efficiency ......................................................................................... 108

C.6 Dimensioning of lightning protection systems ...................................................... 109

C.7 Blade-to-hub connection ..................................................................................... 111

C.8 WTG blade field exposure ................................................................................... 111

C.8.1 General ....................................................................................................... 111

C.8.2 Application ................................................................................................... 112

C.8.3 Field exposure ............................................................................................. 112

Annex D (normative) Test specifications ............................................................................ 113

D.1 General ............................................................................................................... 113

D.2 High-voltage strike attachment tests ................................................................... 113

D.2.1 Verification of air termination system effectiveness ...................................... 113

D.2.2 Initial leader attachment test ........................................................................ 113

D.2.3 Subsequent stroke attachment test .............................................................. 123

D.3 High-current physical damage tests .................................................................... 127

D.3.1 General ....................................................................................................... 127

D.3.2 Arc entry test ............................................................................................... 127

D.3.3 Conducted current test ................................................................................ 132

Annex E (informative) Application of lightning environment and lightning protection

zones (LPZ) ........................................................................................................................ 137

E.1 Lightning environment for blades ........................................................................ 137

E.1.1 Application ................................................................................................... 137

E.1.2 Examples of simplified lightning environment areas ..................................... 137

E.1.3 Area transitions ........................................................................................... 139

E.2 Definition of lightning protection zones for turbines (not blades).......................... 139

E.2.1 General ....................................................................................................... 139

E.2.2 LPZ 0 .......................................................................................................... 140

E.2.3 Other zones ................................................................................................. 141

---------------------- Page: 7 ----------------------
– 6 – IEC 61400-24:2019 © IEC 2019

E.2.4 Zone boundaries .......................................................................................... 142

E.2.5 Zone protection requirements ...................................................................... 143

Annex F (informative) Selection and installation of a coordinated SPD protection in

wind turbines ...................................................................................................................... 146

F.1 Location of SPDs ................................................................................................ 146

F.2 Selection of SPDs ............................................................................................... 146

F.3 Installation of SPDs ............................................................................................ 146

F.4 Environmental stresses of SPDs ......................................................................... 147

F.5 SPD status indication and SPD monitoring in case of an SPD failure .................. 148

F.6 Selection of SPDs with regard to protection level (U ) and system level

immunity ............................................................................................................. 148

F.7 Selection of SPDs with regard to overvoltages created within wind turbines ........ 148

F.8 Selection of SPDs with regard to discharge current (I ) and impulse current

(I ) .................................................................................................................. 148

imp

Annex G (informative) Information on bonding and shielding and installation technique ..... 150

G.1 Additional information on bonding ....................................................................... 150

G.2 Additional information on shielding and installation technique ............................. 151

Annex H (informative) Testing methods for system level immunity tests ............................. 154

Annex I (informative) Earth termination system .................................................................. 159

I.1 General ............................................................................................................... 159

I.1.1 Types of earthing systems ........................................................................... 159

I.1.2 Construction ................................................................................................ 159

I.2 Electrode shape dimensions ............................................................................... 161

I.2.1 Type of arrangement ................................................................................... 161

I.2.2 Frequency dependence on earthing impedance ........................................... 163

I.3 Earthing resistance expressions for different electrode configurations ................ 164

Annex J (informative) Example of defined measuring points ............................................... 167

Annex K (informative) Classification of lightning damage based on risk management ........ 169

K.1 General ............................................................................................................... 169

K.2 Lightning damage in blade .................................................................................. 169

K.2.1 Classification of blade damage due to lightning ........................................... 169

K.2.2 Possible cause of blade damage due to lightning ......................................... 170

K.2.3 Countermeasures against blade damage due to lightning ............................ 171

K.3 Lightning damage to other components ............................................................... 173

K.3.1 Classification of damage in other components due to lightning .................... 173

K.3.2 Countermeasures against lightning damage to other components ................ 173

K.4 Typical lightning damage questionnaire .............................................................. 173

K.4.1 General ....................................................................................................... 173

K.4.2 Sample of questionnaire .............................................................................. 173

Annex L (informative) Monitoring systems .....................................................................

...

IEC 61400-24
Edition 2.0 2019-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 24: Lightning protection
Systèmes de génération d’énergie éolienne –
Partie 24: Protection contre la foudre
IEC 61400-24:2019-07(en-fr)
---------------------- Page: 1 ----------------------
THIS PUBLICATION IS COPYRIGHT PROTECTED
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---------------------- Page: 2 ----------------------
IEC 61400-24
Edition 2.0 2019-07
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
Wind energy generation systems –
Part 24: Lightning protection
Systèmes de génération d’énergie éolienne –
Partie 24: Protection contre la foudre
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 27.180 ISBN 978-2-8322-8688-3

Warning! Make sure that you obtained this publication from an authorized distributor.

Attention! Veuillez vous assurer que vous avez obtenu cette publication via un distributeur agréé.

® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 61400-24:2019 © IEC 2019
CONTENTS

FOREWORD ......................................................................................................................... 11

1 Scope ............................................................................................................................ 13

2 Normative references .................................................................................................... 13

3 Terms and definitions .................................................................................................... 15

4 Symbols and units ......................................................................................................... 21

5 Abbreviated terms ......................................................................................................... 24

6 Lightning environment for wind turbine .......................................................................... 25

6.1 General ................................................................................................................. 25

6.2 Lightning current parameters and lightning protection levels (LPL) ........................ 25

7 Lightning exposure assessment ..................................................................................... 26

7.1 General ................................................................................................................. 26

7.2 Assessing the frequency of lightning affecting a single wind turbine or a

group of wind turbines ........................................................................................... 28

7.2.1 Categorization of lightning events .................................................................. 28

7.2.2 Estimation of average number of lightning flashes to a single or a group

of wind turbines ............................................................................................. 28

7.2.3 Estimation of average annual number of lightning flashes near the wind

turbine (N ) .................................................................................................. 31

7.2.4 Estimation of average annual number of lightning flashes to the service

lines connecting the wind turbines (N ) ......................................................... 31

7.2.5 Estimation of average annual number of lightning flashes near the

service lines connecting the wind turbine (N ) ................................................ 32

7.3 Assessing the risk of damage ............................................................................... 33

7.3.1 Basic equation ............................................................................................... 33

7.3.2 Assessment of risk components due to flashes to the wind turbine (S1) ......... 34

7.3.3 Assessment of the risk component due to flashes near the wind turbine

(S2) ............................................................................................................... 34

7.3.4 Assessment of risk components due to flashes to a service line

connected to the wind turbine (S3) ................................................................ 35

7.3.5 Assessment of risk component due to flashes near a service line

connected to the wind turbine (S4) ................................................................ 35

8 Lightning protection of subcomponents .......................................................................... 36

8.1 General ................................................................................................................. 36

8.1.1 Lightning protection level (LPL) ..................................................................... 36

8.1.2 Lightning protection zones (LPZ) ................................................................... 37

8.2 Blades .................................................................................................................. 37

8.2.1 General ......................................................................................................... 37

8.2.2 Requirements ................................................................................................ 37

8.2.3 Verification .................................................................................................... 38

8.2.4 Protection design considerations ................................................................... 38

8.2.5 Test methods ................................................................................................. 41

8.3 Nacelle and other structural components .............................................................. 42

8.3.1 General ......................................................................................................... 42

8.3.2 Hub ............................................................................................................... 42

8.3.3 Spinner .......................................................................................................... 42

8.3.4 Nacelle .......................................................................................................... 43

8.3.5 Tower ............................................................................................................ 43

8.3.6 Verification methods ...................................................................................... 44

---------------------- Page: 4 ----------------------
IEC 61400-24:2019 © IEC 2019 – 3 –

8.4 Mechanical drive train and yaw system ................................................................. 44

8.4.1 General ......................................................................................................... 44

8.4.2 Bearings ........................................................................................................ 44

8.4.3 Hydraulic systems ......................................................................................... 45

8.4.4 Spark gaps and sliding contacts .................................................................... 46

8.4.5 Verification .................................................................................................... 46

8.5 Electrical low-voltage systems and electronic systems and installations ................ 47

8.5.1 General ......................................................................................................... 47

8.5.2 Equipotential bonding within the wind turbine ................................................ 51

8.5.3 LEMP protection and immunity levels ............................................................ 52

8.5.4 Shielding and line routing .............................................................................. 53

8.5.5 SPD protection .............................................................................................. 54

8.5.6 Testing methods for system immunity tests .................................................... 58

8.6 Electrical high-voltage (HV) power systems .......................................................... 58

9 Earthing of wind turbines ............................................................................................... 60

9.1 General ................................................................................................................. 60

9.1.1 Purpose and scope ........................................................................................ 60

9.1.2 Basic requirements ........................................................................................ 60

9.1.3 Earth electrode arrangements ........................................................................ 60

9.1.4 Earthing system impedance ........................................................................... 61

9.2 Equipotential bonding ........................................................................................... 61

9.2.1 General ......................................................................................................... 61

9.2.2 Lightning equipotential bonding for metal installations ................................... 61

9.3 Structural components .......................................................................................... 62

9.3.1 General ......................................................................................................... 62

9.3.2 Metal tubular type tower ................................................................................ 62

9.3.3 Metal reinforced concrete towers ................................................................... 62

9.3.4 Lattice tower .................................................................................................. 62

9.3.5 Systems inside the tower ............................................................................... 63

9.3.6 Concrete foundation ...................................................................................... 63

9.3.7 Rocky area foundation ................................................................................... 63

9.3.8 Metal mono-pile foundation ............................................................................ 64

9.3.9 Offshore foundation ....................................................................................... 64

9.4 Electrode shape dimensions ................................................................................. 64

9.5 Execution and maintenance of the earthing system ............................................... 65

10 Personal safety .............................................................................................................. 65

11 Documentation of lightning protection system ................................................................ 67

11.1 General ................................................................................................................. 67

11.2 Documentation necessary during assessment for design evaluation...................... 67

11.2.1 General ......................................................................................................... 67

11.2.2 General documentation .................................................................................. 67

11.2.3 Documentation for rotor blades ...................................................................... 68

11.2.4 Documentation of mechanical systems .......................................................... 68

11.2.5 Documentation of electrical and electronic systems ....................................... 68

11.2.6 Documentation of earthing and bonding systems ........................................... 68

11.2.7 Documentation of nacelle cover, hub and tower lightning protection

systems ......................................................................................................... 68

11.3 Site-specific information ........................................................................................ 69

11.4 Documentation to be provided in the manuals for LPS inspections ........................ 69

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11.5 Manuals ................................................................................................................ 69

12 Inspection of lightning protection system ....................................................................... 69

12.1 Scope of inspection .............................................................................................. 69

12.2 Order of inspections .............................................................................................. 70

12.2.1 General ......................................................................................................... 70

12.2.2 Inspection during production of the wind turbine ............................................ 70

12.2.3 Inspection during installation of the wind turbine ............................................ 70

12.2.4 Inspection during commissioning of the wind turbine and periodic

inspection ...................................................................................................... 70

12.2.5 Inspection after dismantling or repair of main parts ........................................ 71

12.3 Maintenance ......................................................................................................... 72

Annex A (informative) The lightning phenomenon in relation to wind turbines ...................... 73

A.1 Lightning environment for wind turbines ................................................................ 73

A.1.1 General ......................................................................................................... 73

A.1.2 The properties of lightning ............................................................................. 73

A.1.3 Lightning discharge formation and electrical parameters ................................ 73

A.1.4 Cloud-to-ground flashes ................................................................................ 74

A.1.5 Upward initiated flashes................................................................................. 80

A.2 Lightning current parameters relevant to the point of strike ................................... 83

A.3 Leader current without return stroke...................................................................... 84

A.4 Lightning electromagnetic impulse, LEMP, effects ................................................. 84

Annex B (informative) Lightning exposure assessment ........................................................ 85

B.1 General ................................................................................................................. 85

B.2 Methodology to estimate the average annual flashes or strokes to the wind

turbines of a wind farm and upward lightning activity in wind turbines ................... 85

B.2.1 General ......................................................................................................... 85

B.2.2 Methodology to determine average annual flashes to turbines of a wind
farm estimation by increase of the location factor to consider upward

lightning from wind turbines ........................................................................... 85

B.2.3 Upward lightning percentage in wind farms .................................................... 89

B.3 Explanation of terms ............................................................................................. 89

B.3.1 Damage and loss ........................................................................................... 89

B.3.2 Composition of risk ........................................................................................ 91

B.3.3 Assessment of risk components ..................................................................... 91

B.3.4 Frequency of damage .................................................................................... 92

B.3.5 Assessment of probability, P , of damage ..................................................... 93

B.4 Assessing the probability of damage to the wind turbine ....................................... 94

B.4.1 Probability, P , that a lightning flash to a wind turbine will cause

dangerous touch and step voltage ................................................................. 94

B.4.2 Probability, P , that a lightning flash to the wind turbine will cause

injury to an exposed person on the structure ................................................. 95

B.4.3 Probability, P , that a lightning flash to the wind turbine will cause

physical damage ............................................................................................ 96

B.4.4 Probability, P , that a lightning flash to the wind turbine will cause

failure of internal systems .............................................................................. 97

B.4.5 Probability, P , that a lightning flash near the wind turbine will cause

failure of internal systems .............................................................................. 97

B.4.6 Probability, P , that a lightning flash to a service line will cause injury

to human beings owing to touch voltage ........................................................ 97

B.4.7 Probability, P , that a lightning flash to a service line will cause

physical damage ............................................................................................ 98

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B.4.8 Probability, P , that a lightning flash to a service line will cause failure

of internal systems ........................................................................................ 99

B.4.9 Probability, P , that a lightning flash near an incoming service line will

cause failure of internal systems .................................................................... 99

B.4.10 Probability P that a person will be in a dangerous place ............................ 100

B.4.11 Probability P that equipment will be exposed to damaging event ................ 100

B.5 Assessing the amount of loss L in a wind turbine .............................................. 100

B.5.1 General ....................................................................................................... 100

B.5.2 Mean relative loss per dangerous event ....................................................... 100

Annex C (informative) Protection methods for blades ......................................................... 102

C.1 General ............................................................................................................... 102

C.1.1 Types of blades and types of protection methods for blades ........................ 102

C.1.2 Blade damage mechanism ........................................................................... 103

C.2 Protection methods ............................................................................................. 104

C.2.1 General ....................................................................................................... 104

C.2.2 Lightning air-termination systems on the blade surface or embedded in

the surface .................................................................................................. 105

C.2.3 Adhesive metallic tapes and segmented diverter strips ................................ 105

C.2.4 Internal down conductor systems ................................................................. 106

C.2.5 Conducting surface materials ....................................................................... 106

C.3 CFRP structural components .............................................................................. 107

C.4 Particular concerns with conducting components ................................................ 108

C.5 Interception efficiency ......................................................................................... 109

C.6 Dimensioning of lightning protection systems ...................................................... 110

C.7 Blade-to-hub connection ..................................................................................... 112

C.8 WTG blade field exposure ................................................................................... 113

C.8.1 General ....................................................................................................... 113

C.8.2 Application ................................................................................................... 113

C.8.3 Field exposure ............................................................................................. 113

Annex D (normative) Test specifications ............................................................................ 114

D.1 General ............................................................................................................... 114

D.2 High-voltage strike attachment tests ................................................................... 114

D.2.1 Verification of air termination system effectiveness ...................................... 114

D.2.2 Initial leader attachment test ........................................................................ 114

D.2.3 Subsequent stroke attachment test .............................................................. 124

D.3 High-current physical damage tests .................................................................... 128

D.3.1 General ....................................................................................................... 128

D.3.2 Arc entry test ............................................................................................... 128

D.3.3 Conducted current test ................................................................................ 133

Annex E (informative) Application of lightning environment and lightning protection

zones (LPZ) ........................................................................................................................ 138

E.1 Lightning environment for blades ........................................................................ 138

E.1.1 Application ................................................................................................... 138

E.1.2 Examples of simplified lightning environment areas ..................................... 138

E.1.3 Area transitions ........................................................................................... 140

E.2 Definition of lightning protection zones for turbines (not blades).......................... 140

E.2.1 General ....................................................................................................... 140

E.2.2 LPZ 0 .......................................................................................................... 141

E.2.3 Other zones ................................................................................................. 142

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E.2.4 Zone boundaries .......................................................................................... 143

E.2.5 Zone protection requirements ...................................................................... 144

Annex F (informative) Selection and installation of a coordinated SPD protection in

wind turbines ...................................................................................................................... 147

F.1 Location of SPDs ................................................................................................ 147

F.2 Selection of SPDs ............................................................................................... 147

F.3 Installation of SPDs ............................................................................................ 147

F.4 Environmental stresses of SPDs ......................................................................... 148

F.5 SPD status indication and SPD monitoring in case of an SPD failure .................. 149

F.6 Selection of SPDs with regard to protection level (U ) and system level

immunity ............................................................................................................. 149

F.7 Selection of SPDs with regard to overvoltages created within wind turbines ........ 149

F.8 Selection of SPDs with regard to discharge current (I ) and impulse current

(I ) .................................................................................................................. 149

imp
Annex G (informative) Information on bonding and shield
...

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