IEC/TR 62066

Surge overvoltages and surge protection in low-voltage a.c. power systems - General basic information

Presents a general overview on the different kinds of surge overvoltages that can occur on low-voltage installations. Typical surge magnitude and duration as well as frequency of occurrence are described. Information on overvoltages resulting from interactions between power system and communications system is also provided.  Additionally, general guidelines are given concerning surge protection means and systems on the basis of availability and risk considerations, including interactions and the need for coordination and consideration of temporary overvoltages in the selection of surge-protective devices.

Prenapetostna zaščita in zaščita v nizkonapetostnih izmeničnih močnostnih sistemih – Splošne osnovne informacije

General Information

• Status: Not Published
• ICS: 29.020 - Electrical engineering in general
• ICS: 91.140.50 - Electricity supply systems
• Technical Committee: TC 64 - Electrical installations and protection against electric shock
• Current Stage: PPUB - Publication issued
• Start Date: 24-Jun-2002
• Ref Project: SIST-TP IEC/TR 62066:2006 - Surge overvoltages and surge protection in low-voltage a.c. power systems - General basic information

Standards Content (Sample)

SLOVENSKI SIST-TP IEC/TR 62066:2006

STANDARD
september 2006
Prenapetostna zaščita in zaščita v nizkonapetostnih izmeničnih močnostnih
sistemih – Splošne osnovne informacije
Surge overvoltages and surge protection in low-voltage a.c. power systems -
General basic information
ICS 29.020; 91.140.50 Referenčna številka
©  Standard je založil in izdal Slovenski inštitut za standardizacijo. Razmnoževanje ali kopiranje celote ali delov tega dokumenta ni dovoljeno

TECHNICAL IEC
REPORT
TR 62066
First edition
2002-06
Surge overvoltages and surge protection
in low-voltage a.c. power systems –
General basic information
Surtensions de choc et protection contre la foudre
dans les réseaux à basse tension –
Informations générales fondamentales
 IEC 2002  Copyright - all rights reserved
No part of this publication may be reproduced or utilized in any form or by any means, electronic or
mechanical, including photocopying and microfilm, without permission in writing from the publisher.
International Electrotechnical Commission, 3, rue de Varembé, PO Box 131, CH-1211 Geneva 20, Switzerland
Telephone: [phone] Telefax: [phone] E-mail: [e-mail]  Web: www.iec.ch
PRICE CODE
Commission Electrotechnique Internationale
XF
International Electrotechnical Commission
Международная Электротехническая Комиссия
For price, see current catalogue

– 2 – TR 62066  IEC:2002(E)
CONTENTS
FOREWORD.7
1 Scope.9
2 Reference documents.9
3 Definitions .10
4 Overvoltages in low-voltage systems .12
5 Lightning overvoltages.13
5.1 General .13
5.2 Origin of lightning surge overvoltages.18
5.3 Lightning surges transferred from MV systems .21
5.4 Surges caused by direct flash to LV lines .23
5.5 Lightning surges induced into LV systems .23
5.6 Examples of induced overvoltages .25
5.7 Overvoltages caused by flashes to the structures or in close vicinity .27
5.8 Recapitulation on lightning overvoltages.30
6 Switching overvoltages.31
6.1 General .31
6.2 Operation of circuit-breakers and switches .35
6.3 Operation of fuses.37
6.4 Frequency of occurrence .38
6.5 Interactions with surge-protective devices .38
6.6 Recapitulation on switching overvoltages .39
7 Temporary overvoltages .40
7.1 General .40
7.2 Magnitude of temporary overvoltages due to MV and LV faults.40
7.3 Temporary overvoltages due to defects in the LV electrical installation.42
7.4 Probability of occurrence and severity of harm .42
7.5 Recapitulation on temporary overvoltage.44
8 System interaction overvoltages .44
8.1 General .44
8.2 Interaction between power system and communications system .45
8.3 Other interactions.46
8.4 Recapitulation on system interactions.46
9 Observations on surge overvoltages and failure rates.46
9.1 General .46
9.2 Using field failure data.47
9.3 Recapitulation of observations on failure rates .48
10 Considerations on system outage/equipment failure/fires .48
10.1 General .48
10.2 Avoiding interference in system operation .49
10.3 Preventing permanent damage.49
10.4 Costs of surge-related interruptions and failures.50
10.5 Recapitulation on outages and failures .52

TR 62066  IEC:2002(E) – 3 –
11 Considerations on the use of surge protection .52
11.1 General .52
11.2 Power system configuration.52
11.3 Types of installation .53
11.4 Occurrence of surges .53
11.5 SPD disconnector.54
11.6 Risk assessment .55
11.7 Recapitulation on the need for surge protection.57
12 Surge protection application .57
12.1 General .57
12.2 Surge protective devices in power distribution systems .58
12.3 Basic system characteristics for SPD selection.59
12.4 Considerations for installation of SPDs.64
12.5 Coordination among SPDs and with equipment to be protected .66
12.6 Recapitulation on surge protection application.67
Annex A (informative)  Complementary information on lightning-related overvoltages .68
Annex B (informative)  Switching overvoltages.79
Annex C (informative)  Complementary information on temporary overvoltages .94
Annex D (informative)  Complementary information on system interaction overvoltages
(see clause 8) .97
Annex E (informative)  Complementary information on SPD application .102
Annex F (informative)  Avoiding overvoltages through good practice for earthing and
cabling.124
Bibliography.128
Figure 1 – Examples of lightning flash coupling mechanisms .13
Figure 2 – Examples of lightning flashes to a complex electrical system .15
Figure 3 – Possible waveforms of lightning current striking ground-based objects.16
Figure 4 – Frequency distribution of peak currents for three types of lightning events .16
Figure 5 – Map of annual thunderstorm days [7] .18
Figure 6 – Direct flash to an overhead line.19
Figure 7 – Example of resistive coupling from lightning protection system .21
Figure 8 – Typical earth coupling mechanisms.22
Figure 9 – Typical overvoltages induced on an LV line by a near lightning flash.24
Figure 10 – Example of estimated frequency of occurrence of prospective induced
lightning overvoltages on LV overhead lines .25
Figure 11 – Model of distribution system used in the simulation .26
Figure 12 – Model for computing dispersion of lightning current
among parallel buildings in an example of TN-C system .28
Figure 13 – Generation of overvoltage by switching an RLC circuit .31
Figure 14 – Typical switching overvoltages .33
Figure 15 – Example of a high-frequency switching surge.33
Figure 16 – Distribution of the rate of rise of switching surges at different locations.34
Figure 17 – Distribution of the rise time of switching surges.34
Figure 18 – Rate of rise of the switching surges and their crest values .35
Figure 19 – Distribution of the duration of the switching surges.35

– 4 – TR 62066  IEC:2002(E)
Figure 20 – Example of distribution of switching surge amplitudes measured
in industrial distribution systems rated 230/400 V .36
Figure 21 – Switching surge during interruption by a miniature fuse [48] .38
Figure 22 – Distribution of the relative frequency of occurrence
of switching surges at different installations .39
Figure 23 – PC/modem connections to the power system
and to the communications system .46
Figure 24 – Example of diversion of lightning current
into the external services (TT system) .61
Figure 25 – Considerations required for the selection of an SPD.63
Figure 26 – Effect of additional connecting lead on the limiting voltage of a varistor .65
Figure 27 – Basic model for energy coordination of SPDs .66
Figure A.1 – Frequency distribution of the lightning peak current I .68
max
Figure A.2 – Frequency distribution of the total lightning charge Q .69
total
Figure A.3 – Frequency distribution of the transient lightning charge Q .69
trans
Figure A.4 – Frequency distribution of the specific lightning energy W/R.70
Figure A.5 – Frequency distribution of the maximum slope of transient current (di/dt) .70
max
Figure A.6 – Frequency distribution of the slope of current (di/dt)
30/90 %
of negative subsequent strokes.71
Figure A.7 – Simplified example with lightning flash to overhead LV line.71
Figure A.8 – Prospective voltages between line and true earth at point of strike (node 1),
at the transformer (node 2) and at the neutral conductor in the consumer installation
(node 3) .72
Figure A.9 – Prospective voltages relative to true earth at node 3 and at node 4 .72
Figure A.10 – Current to earth at the point of strike (node 1), at the transformer (node 2),
and at the consumer installation (node 3) .72
Figure A.11 – Distribution of overvoltage peak magnitudes recorded at the primary
of an MV/LV transformer .73
Figure A.12 – Circuit used for the statistical computation .74
Figure A.13 – Comparison of measured overvoltages [51]
and computed overvoltages (Anastasia).74
Figure A.14 – Model for computing dispersion of lightning current among parallel
buildings (TN-C system) [24].75
Figure A.15 – Dispersion of ligh
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