International Telecommunication Union
ITU-T Study Group 5
Protection against Lightning
Phil Day
Australia
Technical Session on
Home Networks
Geneva, 29/04/2011
Introduction
ITU-T
Study Group 5
o This presentation is about the
protection of Home Network (HN)
equipment and will specifically
cover:
• Protection parts
• Philosophy of protection
• Classification of ports
• Mechanisms of damage
• Risk
29.04.2011
Technical Session - Home Networks - Geneva
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Introduction (cont)
ITU-T
Study Group 5
29.04.2011
• Standards
• Conclusion
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Protection parts
ITU-T
Study Group 5
o Protection of an installation may
require a combination of:
• Lightning protection of the building.
• Resistibility of equipment.
• Protection of incoming lines.
• Earthing and bonding of the
installation.
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Protection parts
ITU-T
Study Group 5
LPS
equipment
SPD
SPD
Telecommunication
cable
main earthing
terminal
earth electrodes
a.c. mains
metallic water pipe
Figure 1
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Protection parts
ITU-T
Study Group 5
29.04.2011
o Protection of the building structure:
• Protection of the building structure,
if necessary, is installed according to
the IEC 62305 series.
• It includes a Lightning Protection
System (LPS) comprising air
terminals, downconductors,
equipotential bonding conductors and
earth terminations.
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Protection parts
ITU-T
Study Group 5
o Resistibility requirements are in
Recommendation K.21:
• “inherent” and “coordination”
requirement for external ports.
• “inherent” requirement for internal
ports.
• “basic’ requirement for general use.
• “enhanced’ requirement for specific
reasons.
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Protection parts
ITU-T
• Special requirements where earthing
and bonding cannot be achieved.
Study Group 5
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Protection parts
ITU-T
Study Group 5
o Protection of incoming lines and
equipment:
• Installation of primary protection on
external lines; mains and external
telecommunication or data lines as
required.
• Installation of protection at the
equipment as required.
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Protection parts
ITU-T
Study Group 5
29.04.2011
o Earthing and bonding
• Earthing is the connection of the
earth bar to earth, usually via an
installed earth electrode.
• Bonding is the interconnection of
earth electrodes and interconnection
of metallic parts to minimise
potential differences
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Protection parts (cont)
ITU-T
Study Group 5
29.04.2011
• SPDs and cable screens are earthed
• IEC 60364-4-44 has the possibility of
bonding the PE to the structure earth
on each floor to reduce loop sizes
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Philosophy of Protection
ITU-T
Study Group 5
o The first method of protection is to
install a Multiservice Surge
Protective Device (MSPD):
• These are described in
Recommendation K.66 (currently
called a Combination Protection Unit
(CPU).
• They provide equipotential bonding
of the ports at the equipment.
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Philosophy of Protection
ITU-T
Study Group 5
29.04.2011
• They will protect against surges
induced into the services and internal
wiring, and against conducted surges
let through by the primary SPD.
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Philosophy of Protection
(cont)
ITU-T
Study Group 5
29.04.2011
o Power and telecommunication
Network operators may install SPDs
in lightning prone areas.
o If not, it is recommended that SPDs
be installed as required.
o These primary SPDs (telecoms and
mains) protect MSPDs, secondary
protection and the house wiring.
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Classification of ports
ITU-T
Study Group 5
o Equipment can have a combination
of internal and external ports:
• External ports are protectable by a
GDT on the telecommunications ports
and a mains SPD on the mains port.
They must comply with a
coordination test.
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Classification of ports
ITU-T
Study Group 5
29.04.2011
• Internal ports require a unique SPD
designed according to IEC 61643.
There is no coordination test in K.21.
• Guidance on classification of ports is
given in K.44 and K.75.
• Incorrect classification may result in
damage.
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Mechanisms of damage
ITU-T
Study Group 5
29.04.2011
o Strike to the structure (S1) may
result in damage to external ports
(conducted surges) and internal ports
(induced surges)
o Strike near to the structure (S2) may
result in damage to internal ports
(induced surges)
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Mechanisms of damage
(cont)
ITU-T
Study Group 5
29.04.2011
o Strike to the services (S3) may result
in damage to external ports
(conducted surges) and internal ports
(conducted surges). This is the work
introduced by NTT. This issue will be
studied over the next few months.
o Strike near to the services (S4) may
result in damage to external ports
(induced surges).
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Practices which may cause
damage
ITU-T
Study Group 5
29.04.2011
o Internal port connected to external
cable.
o The interconnected pieces of
equipment are connected to
different un-bonded electrodes.
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Risk
ITU-T
Study Group 5
29.04.2011
o Risk is covered in some ITU-T
documents but not for damage of
customer equipment.
o Risk is also covered in IEC 62305-2,
but not for damage of customer
equipment.
o Need to consider “loss” versus
frequency of damage.
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Risk (cont)
ITU-T
Study Group 5
29.04.2011
o Recommendation K.hnwr will contain
the information for performing a risk
assessment and also an example risk
assessment.
o The frequency of damage will be
determined.
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Relevant Standards
ITU-T
Study Group 5
o The following ITU-T documents are
relevant.
• K.21, K.44, K.66, K.71, K.74, K.75
and K.hnwr
o The following IEC documents are
relevant
• IEC 60364-4-44, IEC 61000-4-5, IEC
61643 parts 12, 21 and 22 and IEC
62305 series
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Conclusion
ITU-T
Study Group 5
o If we are to prevent damage to HN
equipment we need:
• Adequate resistibility of equipment.
• Correct classification and use of
ports.
• Good installation practices.
• Correct earthing and bonding.
• Protection for external and internal
ports as necessary.
_________________________________________________
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