IEC 61643-12:2008
(Main)Low-voltage surge protective devices - Part 12: Surge protective devices connected to low-voltage power distribution systems - Selection and application principles
Low-voltage surge protective devices - Part 12: Surge protective devices connected to low-voltage power distribution systems - Selection and application principles
IEC 61643-12:2008 describes the principles for selection, operation, location and coordination of SPDs to be connected to 50 Hz to 60 Hz a.c. and to d.c. power circuits and equipment rated up to 1 000 V r.m.s. or 1 500 V d.c. Specific change with respect to the previous edition is the incorporation of Amendment 1, which was not published separately due to the number of changes and pages.
Parafoudres basse tension - Partie 12: Parafoudres connectés aux réseaux de distribution basse tension - Principes de choix et d'application
La CEI 61643-12:2008 décrit les principes relatifs au choix, à la mise en uvre, à l'emplacement et à la coordination des parafoudres à connecter sur des circuits de puissance 50 Hz à 60 Hz en courant alternatif et des circuits en courant continu, et des matériels de puissance allant jusqu'à 1 000 V en valeur efficace ou 1 500 V en courant continu. Le changement spécifique par rapport à l'édition précédente est l'intégration de l'Amendement 1, qui n'a pas été publié séparément en raison du nombre important de modifications et de pages.
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IEC 61643-12
Edition 2.0 2008-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Low-voltage surge protective devices –
Part 12: Surge protective devices connected to low-voltage power distribution
systems – Selection and application principles
Parafoudres basse tension –
Partie 12: Parafoudres connectés aux réseaux de distribution basse tension –
Principes de choix et d'application
IEC 61643-12:2008
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IEC 61643-12
Edition 2.0 2008-11
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
Low-voltage surge protective devices –
Part 12: Surge protective devices connected to low-voltage power distribution
systems – Selection and application principles
Parafoudres basse tension –
Partie 12: Parafoudres connectés aux réseaux de distribution basse tension –
Principes de choix et d'application
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
PRICE CODE
INTERNATIONALE
XG
CODE PRIX
ICS 29.240; 29.240.10 ISBN 978-2-88910-550-2
® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
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CONTENTS
FOREWORD.8
0 Introduction .11
0.1 General .11
0.2 Keys to understanding the structure of this standard .11
1 Scope.13
2 Normative references .13
3 Terms, definitions and abbreviated terms .14
3.1 Terms and definitions .14
3.2 List of abbreviations and acronyms used in this standard .25
4 Systems and equipment to be protected .26
4.1 Low-voltage power distribution systems.26
4.1.1 Lightning overvoltages and currents .27
4.1.2 Switching overvoltages .28
4.1.3 Temporary overvoltages U .28
TOV
4.2 Characteristics of the equipment to be protected .30
5 Surge protective devices .31
5.1 Basic functions of SPDs .31
5.2 Additional requirements.31
5.3 Classification of SPDs .31
5.3.1 SPD: classification.31
5.3.2 Typical design and topologies.32
5.4 Characteristics of SPDs.33
5.4.1 Service conditions described in IEC 61643-1 .33
5.4.2 List of parameters for SPD selection.34
5.5 Additional information on characteristics of SPDs.35
5.5.1 Information related to power-frequency voltages.35
5.5.2 Information related to surge currents .36
5.5.3 Information related to voltage protection level provided by SPDs.37
5.5.4 Information related to SPD failure modes .39
5.5.5 Information related to short-circuit withstand .40
5.5.6 Information related to load current I and to voltage drop (for two-
L
port SPDs or one-port SPDs with separate input and output
terminals) .40
5.5.7 Information related to change of characteristics of SPDs .40
6 Application of SPDs in low-voltage power distribution systems .40
6.1 Installation and its effect on the protection given by SPDs.40
6.1.1 Possible modes of protection and installation .41
6.1.2 Influence of the oscillation phenomena on the protective distance
(called separation distance in some countries) .43
6.1.3 Influence of the connecting lead length.44
6.1.4 Need for additional protection.45
6.1.5 Consideration regarding location of the SPD depending on the
classes of test .46
6.1.6 Protection zone concept .46
6.2 Selection of SPD .48
6.2.1 Selection of U , U , I , I , I and U of the SPD.49
c T n imp max oc
6.2.2 Protective distance .52
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61643-12 © IEC:2008 – 3 –
6.2.3 Prospective life and failure mode.53
6.2.4 Interaction between SPDs and other devices.53
6.2.5 Choice of the voltage protection level U .54
p
6.2.6 Coordination between the chosen SPD and other SPDs .55
6.3 Characteristics of auxiliary devices.57
6.3.1 Disconnecting devices .57
6.3.2 Event counters .57
6.3.3 Status indicator .57
7 Risk analysis .57
Annex A (informative) Typical information given with inquiries and tenders and
explanation of testing procedures .59
A.1 Information given with inquiries .59
A.1.1 System data .59
A.1.2 SPD application considerations .59
A.1.3 Characteristics of SPD .59
A.1.4 Additional equipment and fittings.60
A.1.5 Any special abnormal conditions .60
A.2 Information given with tender.60
A.3 Explanation of testing procedures used in IEC 61643-1 .60
A.3.1 Determination of U for SPDs tested according to class I and class II tests.60
res
A.3.2 Impulse waveshape for assessment of U .61
res
A.3.3 Influence of a back filter on determination of U .61
res
A.3.4 Operating duty test for SPDs .61
A.3.5 TOV failure test .62
A.3.6 Differences in the testing conditions of Type 1 (test class I), 2 (test class II)
and 3 (test class III) SPDs.62
A.3.7 Short-circuit withstand capability test in conjunction with overcurrent
protection (if any) .63
Annex B (informative) Examples of relationship between U and the nominal voltage
c
used in some systems and example of relationship between U and U for ZnO
p c
varistor .64
B.1 Relationship between U and the nominal voltage of the system .64
c
B.2 Relationship between U and U for a ZnO varistor.64
p c
Annex C (informative) Environment – Surge voltages in LV systems .66
C.1 General .66
C.2 Lightning overvoltages.66
C.2.1 Surges transferred from MV to the LV system.67
C.2.2 Overvoltages caused by direct flashes to LV distribution systems.67
C.2.3 Induced overvoltages in LV distribution systems.68
C.2.4 Overvoltages caused by flashes to a lightning protection systems or an area
of close vicinity.68
C.3 Switching overvoltages.69
C.3.1 General description .70
C.3.2 Circuit-breaker and switch operations.70
C.3.3 Fuse operations (current-limiting fuses).71
Annex D (informative) Partial lightning current calculations.72
Annex E (informative) TOV in the low-voltage system due to faults between high-
voltage systems and earth .75
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E.1 General .75
E.2 Example of a TT system – Calculation of the possible temporary overvoltages .76
E.2.1 Possible stresses on equipment in low-voltage installations due to earth
faults in a high-voltage system .76
E.2.2 Characteristics of the high-voltage system .77
E.2.3 TOV in low-voltage system due to faults in the high-voltage system .77
E.2.4 Conclusions .78
E.3 Values of the temporary overvoltages according to IEC 60364-4-44 .78
E.4 Values of the temporary overvoltages for the US TN C-S system.88
Annex F (informative) Coordination rules and principles.90
F.1 General .90
F.2 Analytical studies: simple case of the coordination of two ZnO varistor based SPDs .90
F.2.1 General .90
F.2.2 Conclusion .92
F.3 Analytical study: case of coordination between a gap-based SPD and a ZnO
varistor based SPD.93
F.3.1 General .93
F.3.2 Example of the calculation of the estimated values required for a decoupling
inductance between a gap and a varistor.94
F.3.3 Conclusion .95
F.4 Analytical study: general coordination of two SPDs .95
F.5 Let-through energy (LTE) method .96
F.5.1 General .96
F.5.2 Method.97
Annex G (informative) Examples of application .99
G.1 Domestic application .99
G.2 Industrial application .101
G.3 Presence of a lightning protection system.105
Annex H (informative) Examples of application of the risk analysis .107
Annex I (informative) System stresses .111
I.1 Lightning overvoltages and currents [4.1.1] . 111
I.1.1 Aspects of the power distribution system that affect the need for an SPD .111
I.1.2 Sharing of surge current within a structure .111
I.2 Switching overvoltages [4.1.2] .112
I.3 Temporary overvoltages U [4.1.3] .113
TOV
Annex J (informative) Criteria for selection of SPDs. 114
J.1 U temporary overvoltage characteristic [5.5.1.2].114
T
J.2 SPD failure modes [5.5.4].114
Annex K (informative) Application of SPDs .117
K.1 Location and protection given by SPDs [6.1].117
K.1.1 Possible modes of protection and installation [6.1.1] . 117
K.1.2 Influence of the oscillation phenomena on the protective distance [6.1.2] . 126
K.1.3 Protection zone concept [6.1.6] .127
K.2 Selection of SPDs .129
K.2.1 Selection of U [6.2.1] .129
c
K.2.2 Coordination problems [6.2.6.2].130
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61643-12 © IEC:2008 – 5 –
K.2.3 Practical cases [6.2.6.3] .132
Annex L (informative) Risk analysis .133
L.1 Group A – Environmental.133
L.2 Group B – Equipment and facilities.133
L.3 Group C – Economics and service interruption . 134
L.4 Group D – Safety.135
L.5 Group E – Cost of protection .135
Annex M (informative) Immunity vs. insulation withstand. 136
Annex N (informative) Examples of SPD installation in power distribution boards in
some countries .138
Annex O (informative) Coordination when equipment has both signalling and power
terminals.143
Annex P (informative) Short circuit backup protection and surge withstand . 150
P.1 Introduction .150
P.2 Information single shot 8/20 and 10/350 fuses withstand . 150
P.3 Fuse Influencing factors (reduction) for preconditioning and operating duty test .151
P.4 Specific examples with estimated range of factors for reduction of single shot fuse
withstand.151
Bibliography.153
Figure 1 – Examples of one-port SPDs .19
Figure 2 – Examples of two-port SPDs.20
Figure 3 – Output voltage response of one-port and two-port SPDs to a combination
wave impulse.22
Figure 4 – Maximum values of U according to IEC 60634-4-44.30
TOV
Figure 5 – Examples of components and combinations of components .33
Figure 6 – Relationship between U , U , U and U .35
p c cs
0
Figure 7 – Typical curve of U versus I for ZnO varistors.38
res
Figure 8 – Typical curve for a spark gap .39
Figure 9 – Flowchart for SPD application .41
Figure 10 – Connection Type 1 (CT1) .42
Figure 11 – Connection Type 2 (CT2) .42
Figure 12 – Influence of SPD connecting lead lengths .45
Figure 13 – Need for additional protection .46
Figure 14 – Flowchart for the selection of an SPD .48
Figure 15 – U and U .51
T TOV
Figure 16 – Typical use of two SPDs – Electrical drawing .55
Figure D.1 – Simple calculation of the sum of partial lightning currents into the power
distribution system.72
Figure E.1 – Temporary power-frequency overvoltage caused by an earth fault in the
high-voltage system.76
Figure E.2 – TN systems.79
Figure E.3 – TT systems.80
Figure E.4 – IT system, example a.81
Figure E.5 – IT system, example b.82
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Figure E.6 – IT system, example c1 .83
Figure E.7 – IT system, example c2 .84
Figure E.8 – IT system, example d.85
Figure E.9 – IT system, example e1.86
Figure E.10 – IT system, example e2 .87
Figure E.11 – US TN-C-S System .88
Figure F.1 – Two ZnO varistors with the same nominal discharge current .91
Figure F.2 – Two ZnO varistors with different nominal discharge currents.92
Figure F.3 – Example of coordination of a gap-based SPD and a ZnO varistor based
SPD.95
Figure F.4 – LTE – Coordination method with standard pulse parameters .96
Figure G.1 – Domestic installation .100
Figure G.2 – Industrial installation .103
Figure G.3 – Circuitry of industrial installation.104
Figure G.4 – example for a lightning protection system . 106
Figure I.1 – Example of diversion of lightning current into the external services (TT
system).112
Figure J.1 – Typical curve for U of an SPD .114
T
Figure J.2 – Internal disconnector in the case of a two-port SPD .115
Figure J.3 – Use of parallel SPDs .116
Figure K.1 – Installation of surge protective devices in TN-systems . 118
Figure K.2a –Connection Type 1.119
Figure K.2b – Connection Type 2.
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