Amendment 1 - Low-voltage electrical installations - Part 4-44: Protection for safety - Protection against voltage disturbances and electromagnetic disturbances

The contents of the corrigendum of August 2016 have been included in this copy.

Amendement 1 - Installations électriques à basse tension - Partie 4-44: Protection pour assurer la sécurité - Protection contre les perturbations de tension et les perturbations électromagnétiques

Le contenu du corrigendum d'août 2016 a été pris en considération dans cet exemplaire.

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Publication Date
22-Sep-2015
Current Stage
PPUB - Publication issued
Start Date
23-Sep-2015
Completion Date
23-Sep-2015
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IEC 60364-4-44
Edition 2.0 2015-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
Low-voltage electrical installations –
Part 4-44: Protection for safety – Protection against voltage disturbances and
electromagnetic disturbances
Installations électriques à basse tension –
Partie 4-44: Protection pour assurer la sécurité – Protection contre les
perturbations de tension et les perturbations électromagnétiques
IEC 60364-4-44:2007-08/AMD1:2015-09(en-fr)
---------------------- Page: 1 ----------------------
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---------------------- Page: 2 ----------------------
IEC 60364-4-44
Edition 2.0 2015-09
INTERNATIONAL
STANDARD
NORME
INTERNATIONALE
colour
inside
A MENDMENT 1
AM ENDEMENT 1
Low-voltage electrical installations –
Part 4-44: Protection for safety – Protection against voltage disturbances and
electromagnetic disturbances
Installations électriques à basse tension –
Partie 4-44: Protection pour assurer la sécurité – Protection contre les
perturbations de tension et les perturbations électromagnétiques
INTERNATIONAL
ELECTROTECHNICAL
COMMISSION
COMMISSION
ELECTROTECHNIQUE
INTERNATIONALE
ICS 33.100.10; 33.100.20; 91.140.50 ISBN 978-2-8322-2882-1

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® Registered trademark of the International Electrotechnical Commission
Marque déposée de la Commission Electrotechnique Internationale
---------------------- Page: 3 ----------------------
– 2 – IEC 60364-4-44:2007/AMD1:2015
© IEC 2015
FOREWORD

This amendment has been prepared by IEC technical committee 64: Electrical installations

and protection against electric shock.
The text of this amendment is based on the following documents:
FDIS Report on voting
64/2032/FDIS 64/2073/RVD

Full information on the voting for the approval of this amendment can be found in the report

on voting indicated in the above table.

The committee has decided that the contents of this amendment and the base publication will

remain unchanged until the stability date indicated on the IEC web site under

"http://webstore.iec.ch" in the data related to the specific publication. At this date, the

publication will be
• reconfirmed,
• withdrawn,
• replaced by a revised edition, or
• amended.

IMPORTANT – The 'colour inside' logo on the cover page of this publication indicates

that it contains colours which are considered to be useful for the correct

understanding of its contents. Users should therefore print this document using a

colour printer.
_____________
FOREWORD
Add the following new text:

The reader's attention is drawn to the fact that Annex C lists all of the “in-some-country”

clauses on differing practices of a less permanent nature relating to the subject of this

standard.
440.2 Normative references
Replace the date of IEC 60038 from "1983" to "2009".
Add the following new references:

IEC 60364-5-53:2001, Electrical installations of buildings - Part 5-53: Selection and erection

of electrical equipment - Isolation, switching and control
IEC 60364-5-53:2001/AMD1:2002
IEC 60364-5-53:2001/AMD2:2015
---------------------- Page: 4 ----------------------
IEC 60364-4-44:2007/AMD1:2015 – 3 –
© IEC 2015

IEC 61643-11:2011, Low-voltage surge protective devices – Part 11: Surge protective devices

connected to low-voltage power systems – Requirements and test methods

IEC 61643-22, Low-voltage surge protective devices – Part 22: Surge protective devices

connected to telecommunications and signalling networks – Selection and application

principles
IEC 62305 (all parts), Protection against lightning
443 Protection against overvoltages of atmospheric origin or due to switching

Replace the existing Clause 443, including its title, by the following new title and text:

443 Protection against transient overvoltages of atmospheric origin or due to
switching
443.1 General

Clause 443 specifies requirements for protection of electrical installations against transient

overvoltages of atmospheric origin transmitted by the supply distribution system including

direct strikes to the supply system and against switching overvoltages. Clause 443 does not

specify requirements for protection against transient overvoltage due to direct or nearby

lightning strokes on the structure.

NOTE 1 For risk management for protection against transient overvoltage due to direct or nearby lightning strokes

on the structure, see IEC 62305-2.

In general, switching overvoltages have lower amplitude than transient overvoltages of

atmospheric origin and therefore the requirements regarding protection against transient

overvoltages of atmospheric origin normally cover protection against switching overvoltages.

If no transient overvoltage protection against disturbances of atmospheric origin is installed,

protection against switching overvoltages may need to be provided.

NOTE 2 Overvoltages due to switching can be longer in duration and can contain more energy than the transient

overvoltages of atmospheric origin. See 443.4.

The characteristics of transient overvoltages of atmospheric origin depend on factors such as:

– the nature of the supply distribution system (underground or overhead);

– the possible existence of at least one surge protective device (SPD) upstream of the origin

of the installation;
– the voltage level of the supply system.

NOTE 3 As regards transient overvoltages of atmospheric origin, no distinction is made between earthed and

unearthed systems.

Protection against transient overvoltages is provided by the installation of surge protective

devices (SPDs).
Selection and installation of SPDs shall be in compliance with Clause 534 of
IEC 60364-5-53:2001, IEC 60364-5-53:2001/AMD1:2002 and IEC 60364-5-53/AMD2:2015.

If there is a need for SPDs on the power supply lines, additional SPDs on other Iines such as

telecom lines are also recommended.

Requirements for protection against transient overvoltages transmitted by data transmission

systems are not covered by Clause 443. See IEC 61643-22.
---------------------- Page: 5 ----------------------
– 4 – IEC 60364-4-44:2007/AMD1:2015
© IEC 2015

Clause 443 does not apply to installations where the consequences caused by overvoltages

affect:
a) structures with risk of explosion;

b) structures where the damage may also involve the environment (e.g. chemical or

radioactive emissions).
443.2 Void
443.3 Terms and definitions
443.3.1
urban environment

area with a high density of buildings or densely populated communities with tall buildings

Note 1 to entry: A town centre is an example of an urban environment.
443.3.2
suburban environment
area with a medium density of buildings
Note 1 to entry: Town outskirts are an example of a suburban environment.
443.3.3
rural environment
area with a low density of buildings
Note 1 to entry: The countryside is an example of a rural environment.
443.3.4
surge protective device
SPD

device that contains at least one non-linear component that is intended to limit surge voltages

and divert surge currents

Note 1 to entry: An SPD is a complete assembly, having appropriate connecting means.

Note 2 to entry: This note applies to the French language only.
[SOURCE: IEC 61643-11:2011, 3.1.1]
443.3.5
calculated risk level
CRL

calculated value of risk used to evaluate the need for transient overvoltage protection

Note 1 to entry: This note applies to the French language only.
443.3.6
rated impulse voltage

impulse withstand voltage value assigned by the manufacturer to the equipment or to a part of

it, characterizing the specified withstand capability of its insulation against transient

overvoltages.
[SOURCE: IEC 60664-1:2007, 3.9.2, Modified — symbol added]
443.4 Overvoltage control

Protection against transient overvoltage shall be provided where the consequence caused by

overvoltage affects:
---------------------- Page: 6 ----------------------
IEC 60364-4-44:2007/AMD1:2015 – 5 –
© IEC 2015
a) human life, e.g. safety services, medical care facilities;

b) public services and cultural heritage, e.g. loss of public services, IT centres, museums;

c) commercial or industrial activity, e.g. hotels, banks, industries, commercial markets,

farms.

For all other cases, a risk assessment according to 443.5 shall be performed in order to

determine if protection against transient overvoltage is required. If the risk assessment is not

performed, the electrical installation shall be provided with protection against transient

overvoltage.

However the transient overvoltage protection is not required for single dwelling units where

the total economic value of the electrical installation to be protected is less than 5 times the

economic value of the SPD located at the origin of the installation.

NOTE 1 National Committees can modify the exception criteria related to single dwelling units or to not apply it.

Protection against switching overvoltages should be considered in the case of equipment

likely to produce switching overvoltages or disturbances exceeding the values according to

the overvoltage category of the installation e.g. where a LV generator supply the installation

or where inductive or capacitive loads (e.g. motors, transformers, capacitor banks, etc.),

storage units or high current loads are installed.

NOTE 2 Annex B provides guidance for overvoltage control where utility provided SPDs are installed on overhead

lines.

For a low-voltage installation supplied from a high-voltage distribution network through a

separate transformer (i.e. an industrial application), additional means for protection against

overvoltages due to lightning should be installed on the high-voltage side of the transformer.

443.5 Risk assessment method

NOTE 1 For protection of a structure and its electrical systems against lightning and surges of atmospheric origin,

IEC 62305 applies

Calculated risk level (CRL) is used to determine if protection against transient overvoltages of

atmospheric origin is required. The CRL is found by the following formula
CRL = f / (L × N )
env P g
where

– f is an environmental factor and the value of f shall be calculated according to

env env
Table 443.1.
Table 443.1 – Calculation of f
env
Environment f
env
Rural and suburban environment
85 × F
Urban environment 850 × F

The value of coefficient F shall be taken equal to 1 for all installations. However, National

Committees may adjust the value of coefficient F from 1 to 3 for dwellings.

– N is the lightning ground flash density (flash per km per year) relevant to the location of

the power line and connected structure;

NOTE 2 According to IEC 62305-2:2010, Clause A.1, 25 thunderstorm days per year are equivalent to a value of

2,5 flashes per km per year. This is derived from the formula N = 0,1 × Td, where Td is the number of

thunderstorm days per year (keraunic level).
---------------------- Page: 7 ----------------------
– 6 – IEC 60364-4-44:2007/AMD1:2015
© IEC 2015
– the risk assessment length L is calculated as below:
L = 2 L + L + 0,4 L + 0,2 L
P PAL PCL PAH PCH
where
L is the length (km) of low-voltage overhead line;
PAL
L is the length (km)of low-voltage underground cable;
PCL
L is the length (km)of high-voltage overhead line;
PAH
L is the length (km)of high-voltage underground cable.
PCH
The total length (L + L + L + L ) is limited to 1 km or by the distance from the
PAL PCL PAH PCH

first overvoltage protective device installed in the power network to the entrance of the

installation whichever is the smaller.

If the distribution networks lengths are totally or partially unknown then L shall be taken

PAL
equal to the remaining distance to reach a total length of 1 km.

For example, if only the distance of underground cable is known (e.g. 100 m), then the L

PAL

shall be taken equal to 90 m. An illustration of an installation showing the lengths to consider

is given in Figure 443.1.
PAL
PAH
PCL L
PCH
IEC
PCL
Key
1 origin of the installation
2 LV/HV transformer
3 surge arrestor (overvoltage protective device)
Figure 443.1 – Illustration of an installation showing the lengths to consider

If CRL ≥ 1 000, no protection against transient overvoltages of atmospheric origin is needed;

If CRL < 1 000, protection against transient overvoltages of atmospheric origin is required.

NOTE 3 Examples of calculations of CRL are given in Annex A.
---------------------- Page: 8 ----------------------
IEC 60364-4-44:2007/AMD1:2015 – 7 –
© IEC 2015
443.6 Classification of rated impulse voltages (overvoltage categories)

443.6.1 Purpose of classification of rated impulse voltages (overvoltage categories)

Clause 443.6 gives information on the overvoltage category of the equipment.

NOTE 1 Overvoltage categories are defined within electrical installations for the purpose of insulation

coordination and a related classification of equipment with rated impulse voltages is provided (see IEC 60364-5-

53:2001/AMD2:2015, Table 534.1).

The rated impulse voltage is used to classify equipment energized directly from the low-

voltage electrical installation into overvoltage category.

Rated impulse voltages for equipment selected according to the nominal voltage are provided

to distinguish different levels of availability of equipment with regard to continuity of service

and an acceptable risk of failure.

Inherent overvoltage control based only on the impulse voltage withstand of the equipment in

accordance with IEC 60664-1 might not be sufficient, because:

– transient overvoltages transmitted by the supply distribution system are not significantly

attenuated downstream in most installations. Insulation coordination can be achieved in

the whole installation, by transient overvoltage protection of the equipment corresponding

to the classified rated impulse voltage, reducing the risk of failure to an acceptable level;

– in installations supplied by a completely buried low-voltage system not including overhead

lines, surge currents and partial lightning currents are distributed via the underground

cables;

– equipment is often connected to two different services, e.g. power line and data line. Field

experience shows that much surge related damage is experienced on this kind of
equipment.

It is necessary to consider the rated impulse voltage U (see IEC 60664-1) of the most

sensitive equipment to be protected in the system or, in cases where a temporary loss of

function of equipment is critical, the equipment level immunity (see IEC 61000-4-5).

443.6.2 Rated impulse voltages of equipment and overvoltage categories
The following points shall be noted:

a) Equipment with a rated impulse voltage corresponding to overvoltage category IV is

suitable for use at, or in the proximity of, the origin of the installation, for example

upstream of the main distribution board. Equipment of category IV has a very high impulse

withstand capability providing the required high degree of reliability, and shall have a

rated impulse voltage not less than the value specified in Table 443.2.

NOTE 1 Examples of such equipment include electricity meters, primary overcurrent protective devices and

ripple control units.

b) Equipment with a rated impulse voltage corresponding to overvoltage category III is

suitable for use in the fixed installation downstream of and including the main distribution

board, providing a high degree of availability, and shall have a rated impulse voltage not

less than the value specified in Table 443.2.

NOTE 2 Examples of such equipment include distribution boards, circuit-breakers, wiring systems (see

IEC 60050-826:2004, 826-15-01), including cables, busbars, junction boxes, switches, socket-outlets) in the

fixed installation, and equipment for industrial use and some other equipment, e.g. stationary motors with

permanent connection to the fixed installation.

c) Equipment with a rated impulse voltage corresponding to overvoltage category II is

suitable for connection to the fixed installation, providing a degree of availability normally

required for current-using equipment, and shall have a rated impulse voltage not less than

the value specified in Table 443.2.

NOTE 3 Examples of such equipment include household appliances and similar loads.

---------------------- Page: 9 ----------------------
– 8 – IEC 60364-4-44:2007/AMD1:2015
© IEC 2015

d) Equipment with a rated impulse voltage corresponding to overvoltage category I is only

suitable for use in the fixed installation where SPDs are installed outside the equipment to

limit transient overvoltages to the specified level, and shall have a rated impulse voltage

not less than the value specified in Table 443.2. Therefore, equipment with a rated

impulse voltage corresponding to overvoltage category I should preferably not be installed

at or near the origin of installation.

NOTE 4 Examples of such equipment include those containing electronic circuits like computers, home

electronics, etc.
Table 443.2 – Required rated impulse voltage of equipment U
Nominal Voltage line Required rated impulse voltage of equipment
voltage of the to neutral kV
installation derived from
nominal
voltages a.c.
or d.c. up to
and including
Overvoltage Overvoltage Overvoltage Overvoltage
category IV category III category II category I
(equipment (equipment (equipment with (equipment
with very high with high normal rated with reduced
rated impulse rated impulse impulse voltage) rated impulse
voltage) voltage) voltage)
For example, For example, For example, For example,
energy meter, distribution distribution sensitive
telecontrol boards, domestic electronic
systems switches appliances, tools equipment
socket-outlets
120/208 150 4 2,5 1,5 0,8
b, d
230/400
300 6 4 2,5 1,5
277/480
400/690 600 8 6 4 2,5
1 000 1 000 12 8 6 4
1 500 d.c. 1 500 d.c. 8 6
According to IEC 60038:2009.

In Canada and USA, for voltages to earth higher than 300 V, the rated impulse voltage corresponding to the

next highest voltage in this column applies.
This rated impulse voltage is applied between live conductors and PE.

For IT systems operations at 220-240 V, the 230/400 row shall be used, due to the voltage to earth at the

earth fault on one line.
Annex A – Explanatory notes concerning 442.1 and 442.2

Replace the existing Annex A, including its title, by the following new Annex A and new title:

---------------------- Page: 10 ----------------------
IEC 60364-4-44:2007/AMD1:2015 – 9 –
© IEC 2015
Annex A
(informative)
Examples of calculated risk level CRL for the use of SPDs
A.1 Example 1 – Building in rural environment
Ground flash density N = 1
Environmental factor f = 85
env
Risk assessment length L = 2 L + L + 0,4 L + 0,2 L
P PAL PCL PAH PCH
= (2 × 0,4) + (0,4 × 0,6)
= 1,04
where
L is the length (km) of low-voltage overhead line= 0,4;
PAL
L is the length (km) of high-voltage overhead line= 0,6;
PAH
L is the length (km) of low-voltage underground cable = 0;
PCL
L is the length (km) of high-voltage underground cable = 0.
PCH
CRL = f / (L × N ) = 85 / (1,04 × 1) = 81,7
env P g
In this case, SPD protection shall be installed as the CRL is less than 1 000.
A.2 Example 2 – Building in rural environment powered in HV
Ground flash density N = 0,4
Environmental factor f = 85
env
Risk assessment length L = 2 L + L + 0,4 L + 0,2 L
P PAL PCL PAH PCH
= 0,2 × 1
= 0,2
where
L is the length (km) of low-voltage overhead line = 0;
PAL
L is the length (km) of high-voltage overhead line = 0;
PAH
L is the length (km) of low-voltage underground cable = 0;
PCL
L is the length (km) of high-voltage underground cable= 1.
PCH
CRL = f / (L × N ) = 85 / (0,2 × 0,4) = 1 062,5
env P g

In this case, SPD protection is not mandatory as the CRL is greater than or equal to 1 000.

A.3 Example 3 – Building in urban environment powered by overhead lines
Ground flash density N = 1
Environmental factor f = 850
env
Risk assessment length L = 2 L + L + 0,4 L + 0,2 L
P PAL PCL PAH PCH
= 2 × 0,4 + 0,4 × 0,6
= 1,04
where
---------------------- Page: 11 ----------------------
– 10 – IEC 60364-4-44:2007/AMD1:2015
© IEC 2015
L is the length (km) of low-voltage overhead line = 0,4;
PAL
L is the length (km) of high-voltage overhead line = 0,6;
PAH
L is the length (km) of low-voltage underground cable = 0;
PCL
L is the length (km) of high-voltage underground cable = 0.
PCH
CRL = f / (L × N ) = 850 / (1 × 1,04) = 817
env P g
In this case, SPD protection shall be installed as the CRL is less than 1 000.
A.4 Example 4 – Building in urban environment powered by underground
cables
Ground flash density N = 0,5
Environmental factor f = 850
env
= 2 L + L + 0,4 L + 0,2 L
Risk assessment length L
P PAL PCL PAH PCH
= 1
where
L is the length (km) of low-voltage overhead line = 0;
PAL
is the length (km) of high-voltage overhead line = 0;
PAH
L is the length (km) of low-voltage underground cable= 1;
PCL
is the length (km) of high-voltage underground cable = 0.
PCH
CRL = f / (L × N ) = 850 / (1 × 0,5) = 1 700.
env P g

In this case, an SPD is not mandatory as the CRL is greater than or equal to 1 000.

Annex B – Guidance for overvoltage control by SPDs applied to overhead lines

Replace the existing Annex B, including its title by the following new Annex B and new title:

---------------------- Page: 12 ----------------------
IEC 60364-4-44:2007/AMD1:2015 – 11 –
© IEC 2015
Annex B
(informative)
Guidance on overvoltage control by
SPDs applied to overhead lines

Where an installation is supplied by, or includes, an overhead line and an SPD is required

according to 443.4, the protective control of the overvoltage level may be obtained either by

installing surge protective devices directly in the installation close to the origin of the

installation or, with the consent of the network operator, in the overhead lines of the supply

distribution network.
As an example, the following measures may be applied:

a) in the case of overhead supply distribution networks, overvoltage protection is erected at

network junction points and especially at the end of each feeder longer than 0,5 km.

Surge protective devices should be erected at every 0,5 km distance along the supply

distribution lines. Nevertheless the distance between surge protective devices should in

no case exceed 1 km;

b) if a supply distribution network is erected partly as an overhead network and partly as an

underground network, overvoltage protection in the overhead lines should be applied in

accordance with a) at each transition point from an overhead line to an underground

cable;

c) in a TN distribution network supplying electrical installations, where the protective

measure automatic disconnection of supply is applied, the earthing conductors of the

surge protective devices connected to the line conductors are connected to the PEN

conductor or to the PE conductor;

d) in a TT distribution network supplying electrical installations, where the protective

measure automatic disconnection of supply is applied, surge protective devices are

provided for the line conductors and for the neutral conductor. At the place where the

neutral conductor of the supply network is effectively earthed, an surge protective device

for the neutral conductor is not necessary.
Annex C – Determination of the conventional length, d

Replace the existing Annex C, including its title, by the following new Annex C and new title:

---------------------- Page: 13 ----------------------
– 12 – IEC 60364-4-44:2007/AMD1:2015
© IEC 2015
Annex C
(informative)
List of notes concerning certain countries
Country Clause Text

AT 443.1 In Austria, the protection of all electrical installations against overvoltages by use of

SPDs, installed according to IEC 60364-5-53:2001, Clause 534 and IEC 60364-5-
53:2001/AMD2:2015 is mandatory, irrespective of the categories of consequences
and of any risk assessment method.
NO 443.1 In Norway, every electrical installation shal
...

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