CLC/TS 61643-22:2006

SLOVENSKI STANDARD
01-januar-2007
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Low-voltage surge protective devices -- Part 22: Surge protective devices connected to
telecommunications and signalling networks - Selection and application principles
berspannungsschutzgerte fr Niederspannung -- Teil 22: berspannungsschutzgerte fr den
Einsatz in Telekommunikations- und signalverarbeitenden Netzwerken - Auswahl- und
Anwendungsprinzipien
Parafoudres basse tension -- Partie 22: Parafoudres connects aux rseaux de signaux et
de tlcommunications - Principes de choix et d'application
Ta slovenski standard je istoveten z: CLC/TS 61643-22:2006
ICS:
29.120.50 9DURYDONHLQGUXJD Fuses and other overcurrent
PHGWRNRYQD]DãþLWD protection devices
29.240.10 Transformatorske postaje. Substations. Surge arresters
Prenapetostni odvodniki
2003-01.Slovenski inštitut za standardizacijo. Razmnoževanje celote ali delov tega standarda ni dovoljeno.

TECHNICAL SPECIFICATION
CLC/TS 61643-22
SPÉCIFICATION TECHNIQUE
April 2006
TECHNISCHE SPEZIFIKATION
ICS 29.240; 29.240.10
English version
Low-voltage surge protective devices
Part 22: Surge protective devices connected to telecommunications
and signalling networks -
Selection and application principles
(IEC 61643-22:2004, modified)
Parafoudres basse tension Überspannungsschutzgeräte
Partie 22: Parafoudres connectés für Niederspannung
aux réseaux de signaux Teil 22: Überspannungsschutzgeräte
et de télécommunications - für den Einsatz in Telekommunikations-
Principes de choix et d'application und signalverarbeitenden Netzwerken -
(CEI 61643-22:2004, modifiée) Auswahl- und Anwendungsprinzipien
(IEC 61643-22:2004, modifiziert)

This Technical Specification was approved by CENELEC on 2005-09-10.

CENELEC members are required to announce the existence of this TS in the same way as for an EN and to
make the TS available promptly at national level in an appropriate form. It is permissible to keep conflicting
national standards in force.
CENELEC members are the national electrotechnical committees of Austria, Belgium, Cyprus, the Czech
Republic, Denmark, Estonia, Finland, France, Germany, Greece, Hungary, Iceland, Ireland, Italy, Latvia,
Lithuania, Luxembourg, Malta, the Netherlands, Norway, Poland, Portugal, Romania, Slovakia, Slovenia, Spain,
Sweden, Switzerland and the United Kingdom.

CENELEC
European Committee for Electrotechnical Standardization
Comité Européen de Normalisation Electrotechnique
Europäisches Komitee für Elektrotechnische Normung

Central Secretariat: rue de Stassart 35, B - 1050 Brussels

© 2006 CENELEC - All rights of exploitation in any form and by any means reserved worldwide for CENELEC members.
Ref. No. CLC/TS 61643-22:2006 E

Foreword
The text of the International Standard IEC 61643-22:2004, prepared by SC 37A, Low-voltage surge
protective devices, of IEC TC 37, Surge arresters, together with common modifications prepared by the
Technical Committee CENELEC TC 37A, Low voltage surge protective devices, was submitted to the formal
vote and was approved by CENELEC as CLC/TS 61643-22 on 2005-09-10.
The following date was fixed:
– latest date by which the existence of the CLC/TS
has to be announced at national level (doa) 2006-07-01
__________
- 3 - CLC/TS 61643-22:2006
Contents
Introduction.6
1 Scope.7
2 Normative references.7
3 Terms and definitions.7
4 Description of technologies.8
4.1 Voltage-limiting devices .8
4.1.1 Clamping-type .8
4.1.2 Switching-type.8
4.2 Current-limiting devices .8
4.2.1 Current-interrupting type.8
4.2.2 Current-reducing type.9
4.2.3 Current-diverting type.9
5 Parameters for selection of SPDs and appropriate tests from EN 61643-21 .9
5.1 Controlled and uncontrolled environments .9
5.1.1 Controlled environments.9
5.1.2 Uncontrolled environments.9
5.2 SPD parameters that may affect normal system operation .10
6 Risk management.10
6.1 Risk analysis .11
6.2 Risk identification .11
6.3 Risk treatment.11
7 Application of SPDs.13
7.1 General.13
7.2 Coupling mechanisms.13
7.3 Application, selection and installation of surge protective devices (SPDs) .15
7.3.1 Application requirements for SPDs .15
7.3.2 SPD installation cabling considerations.20
8 Multiservice surge protective devices .23
9 Coordination of SPDs/ITE .23
Annex A (informative) Voltage-limiting devices.25
A.1 Voltage-clamping devices .25
A.1.1 Metal oxide varistor (MOV) .25
A.1.2 Silicon semiconductors .25
A.2 Voltage-switching devices.27
A.2.1 Gas discharge tube (GDT).27
A.2.2 Air gaps.27
A.2.3 Thyristor surge suppressor (TSS) – Fixed voltage types (self-gating) .28
A.2.4 Thyristor surge suppressor (TSS) – Gated types .28

Annex B (informative) Current-limiting devices.29
B.1 Current-interrupting devices.29
B.1.1 Fusible resistor.29
B.1.2 Fuses.30
B.1.3 Thermal fuses .30
B.2 Current-reducing devices.30
B.2.1 Polymer PTC (positive temperature coefficient resistor) .31
B.2.2 Ceramic PTC.31
B.2.3 Electronic current limiters.31
B.3 Current-diverting devices.31
B.3.1 Heat coils.32
B.3.2 Gated thyristor, current operated .32
B.3.3 Thermal switch .33
Annex C (informative) Risk management.34
C.1 Risk due to lightning discharges .34
C.1.1 Risk assessment.34
C.1.2 Risk analysis.34
C.1.3 Risk evaluation.35
C.1.4 Risk treatment.36
C.2 Risk due to power line faults.36
C.2.1 AC power systems .36
C.2.2 DC power systems.37
C.3 Earth potential rise.37
Annex D (informative) Transmission characteristics related to IT systems.38
D.1 Telecommunications systems.38
D.2 Signalling, measurement and control systems .39
D.3 Cable TV systems.39
Annex E (informative) Coordination of SPDs/ITE .40
E.1 Determination of UIN and IIN.40
E.2 Determine the output protective voltage and current waveforms for SPD 1.40
E.3 Compare SPD 1 and SPD 2 values.41
E.4 Necessity of verification of the coordination by testing.42

Figure 1 – SPD installation in telecommunications and signalling networks. 12
Figure 2 – Coupling mechanisms . 14
Figure 3 – Example of a configuration of the lightning protection concept . 16
Figure 4 – Example of a configuration according to the zones(Figure 2). 18
Figure 5 – Example of protecting measures against common-mode voltages and
differential mode voltages of the data (f) and supply voltage input (g) of an ITE . 19
Figure 6 – Influence of the voltages U and U on the protection level U
L1 L2 P
caused by the inductance of the leads . 20

- 5 - CLC/TS 61643-22:2006
Figure 7 – Removal of the voltages U and U from the protector unit
L1 L2
by connecting leads to a common point. . 21
Figure 8 – Necessary installation conditions of a three, five or multi-terminal SPD
with an ITE for minimizing the interference influences on the protection level . 22
Figure 9 – Coordination of two SPDs . 23
Figure A.1 – Circuit for voltage-clamping devices . 25
Figure A.2 – Circuit for voltage-switching devices . 27
Figure B.1 – Circuit for interrupting devices . 29
Figure B.2 – Circuit for current-reducing devices . 30
Figure B.3 – Circuit for current-diverting devices. 32
Figure C.1 – Risk evaluation procedure . 35
Figure E.1 – Coordination verification process . 41

Table 1 – Responsibility for managing the protective measures . 11
Table 2 – Coupling mechanisms . 15
Table 3 – Selection aid for rating SPDs for the use in (zone) interfaces
according to IEC 61312-1 and EN 61000-4-5. 17
Table C.1 – AC overhead power systems. 36
Table C.2 – AC underground electric cables . 37
Table C.3 – DC overhead power systems . 37
Table C.4 – DC underground electric cables . 37
Table D.1 – Transmission characteristics for telecommunications systems in access networks. 38
Table D.2 – Transmission characteristics of IT systems in customer premises . 39
Table D.3 – Transmission characteristics of cable TV-systems . 39

Introduction
This TS is a guide for the application of SPDs to telecommunications and signalling lines and those SPDs
which have telecom or signalling SPDs in the same enclosure with power line SPDs. Definitions,
requirements and test methods are given in EN 61643-21. The decision to use SPDs is based on an
analysis of the risks that are seen by the network or system under consideration. Because
telecommunications and signalling systems may depend on long lengths of wire, either buried or aerial,
the exposure to overvoltages from lightning, power line faults and power line/load switching, can be
significant. If these lines are unprotected, the resultant risk to information technology equipment (ITE) can
also be significant. Other factors that may influence the decision to use SPDs are local regulators and
insurance stipulations. This TS provides indications for evaluating the need for SPDs, the selection,
installation and dimensioning of SPDs and for achieving coordination between SPDs and between SPDs
and ITE installed on telecommunication and signal lines.
Coordination of SPDs assures that the interaction between them, as well as between an SPD and the ITE
to be protected will be realized. Coordination requires that the voltage protection level, U , and let-through
p
current, I , of the initial SPD does not exceed the resistibility of subsequent SPDs or the ITE.
p
In general, the SPD closest to the source of the impinging surge diverts most of the surge: a downstream
SPD will divert the remaining or residual surge. The coordination of SPDs in a system is affected by the
operation of the SPDs and the equipment to be protected as well as the characteristics of the system to
which the SPDs are connected.
The following variables should be reviewed when attempting to attain proper coordination:
− waveshape of the impinging surge (impulse or AC);
− ability of the equipment to withstand an overvoltage/overcurrent without damage;
− installation, e.g. distance between SPDs and between SPDs and ITE;
− SPD voltage-limiting levels and response times.
The performance of an SPD and its coordination with other SPDs can be affected by exposure to
previous transients. This is especially true for transients which approach the limit of the capacity of the
SPD. If there is considerable doubt concerning the number and severity of the surges handled by the
SPDs under consideration, it is suggested that SPDs with higher capabilities be used.
One of the direct effects of poor coordination may be bypassing of the SPD closest to the surge source,
with the result that the following SPD will be forced to handle the entire surge. This can result in damage
to that SPD.
Lack of proper coordination can also lead to equipment damage and, in severe cases, may lead to a fire
hazard.
There are several technologies used in the design of the SPDs covered in this TS. These are explained in
the main text and also in informative Annexes A and B.

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1 Scope
This TS 61643-22 describes the principles for the selection, operation, location and coordination of SPDs
connected to telecommunication and signalling networks with nominal system voltages up to
1 000 V r.m.s. a.c. and 1 500 V d.c.
This TS also addresses SPDs that incorporate protection for signalling lines and power lines in the same
enclosure.
2 Normative references
The following referenced documents are indispensable for the application of this document. For dated
references, only the edition cited applies. For undated references, the latest edition of the referenced
document (including any amendments) applies.
EN 61000-4-5:1995, Electromagnetic compatibility (EMC) – Part 4-5: Testing and measurement
techniques – Surge immunity test (IEC 61000-4-5:1995)
EN 61643-11:2002, Low-voltage surge protective devices – Part 11: Surge protective devices connected
to low-voltage power systems - Requirements and tests (IEC 61643-1:1998 + corr. Dec. 1998, mod.)
EN 61643-21:2001, Low-voltage surge protective devices – Part 21: Surge protective devices connected
to telecommunications and signalling networks – Performance requirements and testing methods
(IEC 61643-21:2000 + corr. Mar. 2001)
IEC 61312-1:1995, Protection against lightning electromagnetic impulse – Part 1: General principles
IEC 61312-2:1999, Protection against lightning electromagnetic impulse (LEMP) – Part 2: Shielding of
structures, bonding inside structures and earthing
ITU-T K.31:1993, Bonding configurations and earthing of telecommunication installations inside a
subscriber's building
3 Terms and definitions
For the purposes of this document, the following definitions apply.
3.1
resistibility
ability of an SPD or information technology equipment (ITE) to withstand an overvoltage or overcurrent
event without damage
1)
NOTE This definition is derived from EN 61663-2 [1] and is modified for this application. The equipment can lose some function
during the overvoltage/overcurrent, but works correctly after the application of the overvoltage/ overcurrent.
3.2
multiservice surge protective device
surge protective device providing protection for two or more services such as power, telecommunications
and signalling in a single enclosure in which a reference bond is provided between services during surge
conditions
———————
1)
Figures in square brackets refer to the bibliography.

4 Description of technologies
The following is a short description of various surge protection component technologies. More details are
available in Annexes A and B.
4.1 Voltage-limiting devices
These shunt-connected SPD components are non-linear elements that limit overvoltages that exceed a
given voltage by providing a low impedance path to divert currents. This voltage, U , is chosen to be
c1
greater than the maximum peak system voltage in normal operation. At the maximum system operating
voltage, the SPD’s leakage current should not interfere with normal system operation.
Multiple components may be used to form assemblies. Connecting voltage-limiting surge protective
components in series results in higher voltage protection levels. Parallel component connection will
increase the surge current capability of the assembly. However, care should be taken to assure current
sharing between the parallel components.
Some technologies, e.g. metal oxide varistors, have voltage-current characteristics that are inherently
symmetrical for positive and negative voltage polarities. Such devices are classified as symmetrical bi-
directional. Devices having positive and negative current-voltage characteristics with the same basic
shape, but with significantly different characteristic values are classified as asymmetrical bi-directional.
Other technologies, e.g. PN semiconductor junctions, have voltage-current characteristics that are
inherently different for positive and negative voltage polarities.
4.1.1 Clamping-type
These SPD components have continuous voltage-current characteristics. Generally, this will mean that
the protected equipment will be exposed to a voltage above the SPD’s threshold level for most of the
voltage impulse duration. As a result, these SPD components will absorb substantial energy during the
overvoltage.
4.1.2 Switching-type
These SPD components have a discontinuous current-voltage characteristic. At a designed voltage, they
switch to a low-voltage state. In this low-voltage state, the energy absorbed is low compared to that of
other SPDs that ”clamp” the voltage at a specific protection level. As a result of this switching action,
protected equipment will be subjected to a voltage above the normal system voltage for only a very short
time. If the system’s operating voltage and current exceed the reset characteristics of the switching-type
device, these devices remain in the conducting state. Appropriate SPD selection and circuit design will
allow the SPD to recover to a high resistance state under normal system voltage and currents.
4.2 Current-limiting devices
To limit an overcurrent, the protection device has to stop or reduce the current flowing to the protected
load. There are three possible methods: interruption, reduction or diversion. The majority of the
technologies used for overcurrent protection are thermally activated, resulting in relatively slow response
operating times. Until the overcurrent protection operates, the load, and possibly the SPDs, have to be
capable of withstanding the surge.
4.2.1 Current-interrupting type
These devices open the circuit path for the surge current to the SPD or ITE (see Figure B.1). Sudden
opening of a current-carrying circuit usually results in arcing, particularly if the current is at its peak. This
arcing has to be controlled to prevent a safety hazard. After interruption, maintenance is required to
restore service. One example of a current-interrupting device is a fuse.

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4.2.2 Current-reducing type
These devices reduce the current flow by effectively inserting a large series resistance with the load (see
Figure B.2). An example of a current-reducing type used for this action is a self-heating positive
temperature coefficient (PTC) thermistor. Overcurrents cause resistive heating of the PTC thermistor,
which results in the thermistor’s temperature exceeding its threshold temperature (typically 120 °C).
Consequently, this causes a thermistor resistance change from ohms to hundreds of kilo-ohms, thereby
reducing the current. The lower current, after changing to a high resistance, maintains the PTC
thermistor's temperature, forcing the PTC thermistor to remain in the high resistance state. A thermistor
dissipation of typically about 1 W is needed to maintain the temperature, e.g. 5 mA from a 200 V a.c.
overvoltage. If the system’s operating voltage and current do not exceed the PTC reset characteristics,
the PTC thermistor will cool and return to a low resistance value after the surge.
4.2.3 Current-diverting type
These devices effectively place a short-circuit across the network at the point of installation (see
Figure B.3). Activation occurs due to temperature rise of the voltage-limiting type or load current sensing.
Although the load is protected, the surge current in the network feed is the same or greater. After
operation, maintenance may be required to restore service.
5 Parameters for selection of SPDs and appropriate tests from EN 61643-21
This clause discusses the parameters of SPDs and their relevance to the operation of the SPDs and the
normal operation of the networks to which they are connected. These parameter values can be used to
form the basis for comparison amongst SPDs and also to provide guidance in their selection for signalling
and power systems. Values for these parameters are available from SPD manufacturers and suppliers.
Verification of the values, or obtaining them when not provided by suppliers, should be performed using
the tests and methods described in EN 61643-21.
5.1 Controlled and uncontrolled environments
The SPD parameters should be suitable for the intended environment.
5.1.1 Controlled environments
− Temperature range: -5 °C to 40 °C
− Humidity range: 10 % RH to 80 % RH
− Air pressure range: 80 kPa to 106 kPa
The controlled environment is one within the managed environment of a building or other infrastructure.
This controlled environment will be at the very least naturally heated and cooled but will be protected
against the extremes of the natural environment.
5.1.2 Uncontrolled environments
− Temperature range: -40 °C to 70 °C
− Humidity range: 5 % RH to 96 % RH
− Air pressure range: 80 kPa to 106 kPa

5.2 SPD parameters that may affect normal system operation
The essential characteristics for the operation of SPDs having voltage-limiting or both voltage-limiting and
current-limiting functions used in protecting telecommunication and signalling systems are as follows:
− maximum continuous operating voltage U ;
c
− voltage protection level U ;
p
− impulse reset;
− insulation resistance (leakage current);
− rated current.
SPDs should conform to application-specific requirements. Some SPD parameters can influence the
transmission characteristics of the network. These are listed below, as follows:
− capacitance;
− series resistance;
− insertion loss;
− return loss;
− longitudinal balance;
− near end cross-talk (NEXT).
Therefore, SPDs may need to be tested using selected tests from EN 61643-21. Annex D provides
information about information technologies and some of their transmission characteristics that have to be
taken into account when applying SPDs to these systems.
6 Risk management
The need for protective measures (e.g. protection with SPDs) for Information Technology Systems should
be based on a risk assessment, considering the probability of overvoltage and overcurrent. The
assessment of all parts of the Information Technology System should attain a well coordinated protection
of the whole network. This takes into account the consequences of the loss of service for the customer
and network operator, the importance of the system (e.g. hospitals, traffic control), the electromagnetic
environment at the particular site (probability of damages) and cost related to repair.
The decision to install protective measures should be assessed based on
− the risk of damage to the network outside or inside the structure,
− the tolerable risk of damage.

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For the structure and network inside the structure, the customer should analyse these two values. For the
network outside the structure, the network operator should analyse them. As the weighting of risk
components can lead to different protection results at the interconnection between the operator's network
and private network (see Figure 1, “NT”-point), the following Table 1 gives a general overview of the
responsibility for managing the protective measures.
Table 1 – Responsibility for managing the protective measures
Information Technology system Responsibility
Installation inside the structure; private network Customer
Installation outside the structure; operator's network Network operator
Interconnection between operator's network and private Network operator or customer
network (NT)
Information technology equipment ITE Customer (see NOTE)
Additional protective measures based on risk assessment Customer
NOTE  Resistibility requirements of telecommunications equipment are given in the ITU-T K series as referenced in
IEC 61663-2 [1], they are implemented by the ITE manufacturer.
6.1 Risk analysis
Risk analysis takes into consideration the following electromagnetic phenomena:
− power induction;
− lightning discharges;
− earth potential rise;
− power contact.
6.2 Risk identification
Risk identification takes into account economic aspects such as
− costs (high repair costs of inadequately protected equipment versus no repair costs of adequately
protected equipment, probability of occurrence of damaging electromagnetic phenomena),
− intended application,
− the protective measures in installations,
− continuity of the service,
− serviceability of the equipment (equipment installed in difficult-to-reach places, e.g. high mountains).
6.3 Risk treatment
Risk treatment considers reduction of damage to the whole of the communication network, i.e. all types of
networks, public and private, including all kinds of transmission or terminal equipment. The installation of
SPDs can be subject to requirements and/or restrictions given by the network operator, network authority
and system manufacturer (see Figure 1). For further information concerning risk management see
Annex E.
ITE
SPD/S
SPD/S
E
SPD/S
ITE
SPD/S
Signalling network
SPD/S/N TTE
S E
SPD/N SPD/N SPD/N SPD/S/N NT SPD/S/N TTE
Operators’ network Private network
Operators’ or
private network
Telecommunications network
Key
SPD/N SPD requirements/restrictions given by network operator/authority
SPD/S SPD requirements/restrictions may be given by system manufacturer
SPD/S/N SPD requirements/restrictions may be given by system manufacturer and network operator/authority
S switching centre
E equipment (e.g. multiplexer)
NT network termination
ITE information technology equipment or processing control
TTE telecommunication terminal equipment
Figure 1 – SPD installation in telecommunications and signalling networks

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7 Application of SPDs
7.1 General
When considering the application of SPDs to a telecommunications and signalling network, it is important
to determine the probable overvoltage and overcurrent sources and how energy from these sources is
coupled into the network. These are shown in Figure 2, as are means for reducing the amount of energy
coupled into the network.
7.2 Coupling mechanisms
The major sources of transient that pose a threat to telecommunications and signalling systems are due
to lightning and the electric power system. The means of coupling include a lightning direct strike and
direct contact from the power system as well as capacitive, inductive and radiative coupling from both
sources. A fourth coupling mechanism consists of earth potential rise which can also come from both
sources.
Protective measures should be coordinated with the system to be protected. Wherever protective
measures are needed in a building, an equipotential bonding bar (EBB) should be installed. A further
important measure is to minimize the impedance of all bonding connections from the equipment to the
building EBB. The metallic shield of the cable, if used, should be continuous, i.e. it should be connected
across all splices, regenerators, etc. along the length of the cable. It should also be connected to the
EBB, preferably directly or through an SPD or a combination of an SPD and a capacitor (to avoid
corrosion problems and 50 Hz noise), at the ends of the cable. Another measure is to provide the
incoming services with adequate SPDs so that transient overvoltages and overcurrents are reduced to
system compatible levels. The SPDs should be located as close as possible to a common entry area in
the structure, e.g. a building or cabinet through which all incoming services enter. If some distance is
required between protected equipment and the cable entrance area, particular attention should be paid to
reduce the impedance of the bonding conductors of the SPD and equipment to a minimum value.
Figure 2 depicts the way in which energy from lightning and a.c. sources is coupled into a structure
containing the exposed equipment. It should be noted that while direct strikes result in the need for the
more robust SPDs as seen in Table 2, they are also the most infrequent. The information contained in
Clause 6, dealing with risk management, will provide guidance to understanding the figure and table. For
the sake of simplicity, the figure illustrates direct lightning travelling down a single conductor. In reality,
the system will have many down conductors and the direct lightning current will be shared among them.
As a result of this current sharing, the magnitudes of surge voltages, by mechanisms of inductive
coupling, would be subsequently reduced.
Figure 2 shows a typical structure with a lightning protection system (containing attachment terminals, a
bonding network and an earthing system), in-coming services (possibly telephone or another
telecommunications connections (h) and power (g)) as well as installed equipment. The figure
incorporates single-point lightning protection bonding (d). This arrangement, which is recommended, sees
all incoming services bonded on entry to the building to a single common earth point (main EBB). This
common earth point is single-point connected to the lightning down-conductor and has a separate earth
for power compliance reasons. All services entering the building should be connected to this earthing
point to obtain an equipotential environment for all building systems. The figure also shows a local
equipotential bonding arrangement at or near the building equipment (floor EBB). Within this
arrangement, an equipotential environment is created for each floor, equipment room and possibly even
an equipment rack by a common earth reference point at cable entry. All services entering the area are
earth referenced to the point (either through surge protection devices or directly). This local equipotential
bonding point is single-point connected to the main building bond and does not have a separate
connection to earth.
Table 2 shows the relationship between the source of transients and coupling mechanism (e.g. direct
strike resistive coupling). The voltage and current waveshapes and test categories are selected from
Table 3 of EN 61643-21.
(S1)
(f) ITE (g)
(d)
(2)
(2)
(1) (2)
(3) (4)
(S2)
(S4)
(d)
(3)
(S3)
(h) (1) (5)
(g)
(p)
(e3) (e2) (e1)
Key
(d) equipotential bonding bar (EBB) (Note – see IEC 61312 series for earthing and bonding services entering the structure
in different locations)
(e1) building earth
(e2) lightning protection system earth
(e3) cable shield earth
(f) information technology/telecommunication port
(g) power supply port
(h) information technology/telecommunication line or network
(p) earthing electrode
(S1) direct lightning to the structure
(S2) lightning near to the structure
(S3) direct lightning to the telecommunication/power line
(S4) lightning near to the telecommunication/power line
(1) . (5) coupling mechanisms, see Table 2
Figure 2 – Coupling mechanisms

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Table 2 – Coupling mechanisms
Lightning to
Direct lightning to Lightning to earth Direct lightning
earth near
Source of the structure near the structure to the line AC
the line
transients influence
b
(S1) (S2) (S3)
(S4)
Coupling Resistive Induction a Resistive Induction Resistive
Induction
(1) (2) (1, 5) (3) (4)
(2)
Voltage wave-
– 1,2/50 1,2/50 – 10/700 50/60 Hz
shape (µs)
Current wave-
d
10/350 8/20 8/20 5/300 –
10/350
shape (µs)
Preferred test
D1 C2 C2 D1 B2 A2
c
category
NOTE (1) – (5) see Figure 2, coupling mechanisms.
a
Also applies for capacitive/inductive couplings of switching in adjoining power supply networks.
b
Due to the significant reduction of fields with increased distance coupling effects from afar, lightning strike may be
negligible.
c
See Table 3 of EN 61643-21.
d The simulated direct lightning strike test impulse is described by IEC/TC 81 as a peak current value and total charge. A
typical waveshape that can achieve these parameters is a double exponential impulse, 10/350 being used in this example.

7.3 Application, selection and installation of surge protective devices (SPDs)
7.3.1 Application requirements for SPDs
SPDs should comply with EN 61643-21 and with specifications that refer to the system to be protected.
For SPD applications in the public power supply system, other or additional requirements may apply, and
will not be described in the following subclauses. The following subclauses deal with the application of
SPDs in information technology systems inside structures.
7.3.1.1 Selection of SPDs for reducing lightning effects
The action of limiting surges causes energy to be absorbed or reflected by the SPD. SPDs should be
specified by the manufacturer in accordance with Table 3 of EN 61643-21, including details of peak pulse
current and waveshape (for example 5 kA (8/20)).
When determining protection measures, protection requirements for each of the various protection
locations (see Figure 3) should be considered. Protection devices should be applied in a cascade
arrangement at the zone interfaces (for management of lightning protection zones, consult
IEC 61312-1).The zone concept is especially relevant when a physical LPS exists. For example, the first
protection level (j, m), located at the entrance of the building, mainly serves to protect the installation
against destruction. This protection should be designed and rated for such a threat. The output of this
protection has a reduced surge energy that becomes the input to the subsequent downstream protection.
The following protection levels (k, l and n, o) further reduce the surge level to a value that is acceptable
for subsequent downstream protection or equipment (also see 7.3.1.2).
Figure 3 is an example of star configuration in agreement with IEC 61312 series and ITU-T K.31.

Depending on the over-voltage/over-current threat levels and SPDs characteristics, a single SPD can be
used to protect the equipment within a building. Several protection levels can be determined by means of
a combination protection circuit in one SPD. Depending on equipment locations, a single SPD can be
used to protect multiple zones within a building.
When cascading SPDs exist, the coordination conditions of Clause 9 should be considered.

(I )
B
LPZ 0
A
LPZ 1
LPZ 2
LPZ 3
LPZ 0
B
(o)
(I)
(f) ITE(g)
(d)
(k)
(n)
I
P
C
(d)
(j) (m)
(h)
0,5 I
B
(g)
0,5 I
B
Key
(d) equipotential bonding bar (EBB) at the lightning protection zone (LPZ) boundary
(f) information technology/telecommunication port
(g) power supply port/line
(h) information technology/telecommunication line or network
I partial surge current of a lightning current
PC
I direct lightning current according to IEC 61312-1, which causes lightning partial currents I within buildings via
B PC
different coupling paths
(j, k, l) SPD according to Table 3 (see also Table 3 of EN 61643-21)
(m, n, o) SPD according to test classes I, II and III of EN 61643-11
(p) earthing conductor
LPZ 0 …3 lightning protection zone 0 … 3 according to IEC 61312-1
A A
Figure 3 – Example of a configuration of the lightning protection concept

- 17 - CLC/TS 61643-22:2006
7.3.1.2 Selection of SPDs to reduce transients
SPDs should be selected according to the cascading of the protection zones of 7.3.1.1 and the protection
levels of Table 3 (refer to Clause 9 for coordination). For this purpose, the protection devices are selected
in such a way that the limiting voltage indication U for the SPD is lower than the voltage value that has to
p
be observed in the next SPD or ITE (see Figure 4).
The selection with respect to lightning protection zones in Table 3 assumes that parts of the total lightning
current I on the zone interface LPZ0 /LPZ1 are resistively coupled into the information technology
B
system via the SPD (j) (partial lightning current I ) The resultant lightning wave shape which propagates
PC
in the information technology system will be modified by the system wiring and SPD operation. If the
protection level of SPD (j) is higher than the equipment resistibility level, then install an additional SPD
with an appropriate protection level which is coordinated with SPD (j). Alternatively, replace SPD (j) with
an SPD which has a suitable protection level.
Surge currents, which are induced by the electromagnetic effects of a lightning stroke, or by let-through
transients of pre-installed limiting installations (SPDs), are represented by the lightning current flow 8/20.
Voltages due to strikes close to information technolo
...