Global Standardization Activities

Trends in Standardizing Protection against
Electromagnetic Environment Effects in ITU-T SG5
Tetsuya Tominaga† and Ryuichi Kobayashi
Abstract
With the increase in ubiquitous communication based on wireless technology, protection against electromagnetic environment effects is becoming more important. This includes ensuring compatibility
between electrical equipment (which emits electromagnetic noise) and wireless communication systems
and protecting radio base stations against lightning to achieve secure and safe telecommunication. ITUT SG5 is responsible for studies related to protecting telecommunication equipment and facilities againstelectromagnetic effects and for ensuring human safety from electromagnetic effects.

1. Ubiquitous and broadband
Technologies for ubiquitous communication, like
RF-ID (radio frequency identification) systems andwireless LAN (local area network) systems, are basedon short-distance wireless communication. The number of such appliances is forecast to increase explosively in the future. On the other hand, broadband
communication technologies based on high-speed
telecommunication need a lot of radio frequencies
and higher frequencies than used to date. Therefore,
the probability of electromagnetic interference occurring will increase. Electromagnetic waves that are
unintentionally radiated from electrical information

technology equipment (ITE) are called “emission” asshown in Fig. 1. They affect wireless systems. Moreover, the electromagnetic waves radiated from wireless systems induce noise in metallic cables used fortelecommunication. However, metallic-cabletelecommunication systems need to maintain theirtelecommunication quality even when wireless systems are used nearby. In the study period from 2000
to 2004, ITU-T SG5*1 [1] investigated electromagnetic environment effects and discussed emission
limits for and methods of measuring wired telecommunications networks in situ when actual interference occurs, with the aim of preventing interference
between various telecommunication systems. The

Wireless communication

Unwanted emission from ITE

Fig. 1. Unwanted emission in ubiquitous communication.
† NTT Energy and Environment Systems Laboratories
Musashino-shi, 180-8585 Japan
E-mail: tominaga.tetsuya@lab.ntt.co.jp

68*1 ITU-T SG5: International Telecommunication Union Telecommunication Standardization Sector Study Group 5.

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results became Recommendation K.60. This recommendation’s limits and measurement methods cover awider frequency range (from 9 kHz to 3 GHz) than theexisting emission recommendations. In the next study
period, items scheduled for discussion include limits
for newer communication systems, such as power line
communication (PLC), and emission evaluation methods for next-generation broadband communication.
2. Changes in telecommunication system usage
conditions
The number of cellular phone users has increased
rapidly in the last few years. This raises the possibility of a person with a cellular phone in his/her pocket
being near telecommunication equipment, as shownin Fig. 2. However, the immunity of telecommunication equipment against radio waves from cellularphones is not covered by any recommendations.
Therefore, there has been discussion to revise K.43
(generic immunity recommendation) and K.48 (product family electromagnetic compatibility (EMC)
requirements). The revision states that telecommunication equipment should have sufficient immunity inthe frequency band used by cellular phones. NTT isalso planning to revise its immunity technicalrequirements [2] corresponding to K.43 and K.48.
Thus, revisions of existing recommendations to copewith telecommunication system usage conditions
will be an important subject in the future. In otherexamples, when the transmission rate fell even slightly, equipment failed some criteria of the existing
immunity test. However, most services are provided
on a best-effort basis, like ADSL (asymmetric digital
subscriber line), with the expectation that speed will
decrease with distance from the telecommunication
center, etc. For such IP (Internet protocol) system ser-vices, discussion of what kinds of failure criteria areappropriate has been scheduled.
An increase in the number of cellular phones alsomeans an increase in the number of radio base stations, which are usually installed high above theground and are thus vulnerable to damage from lightning (Fig. 3). Therefore, protection of the radio basestation itself and of neighboring buildings was considered. The setup conditions for radio base stations
vary widely, so the first discussion covered the protection of general radio base stations against lightning discharges and protection of radio base stations
sited on power line towers. The protection procedures, which include earthing, bonding, shielding,and installation of surge protective devices, weresummarized and the results became new recommendations K.56 and K.57, respectively. Discussion ofprotection procedures in various installations andprocedures for reducing the effect of the neighborhood has been scheduled.
3. Changes for using telecom centers and cables
Network operators around the world are tending toincrease co-location use of telecommunication centerbuildings, as shown in Fig. 4. Thus, it is necessary toprovide reliable telecommunications to customers
even when systems from multiple operators areinstalled in a building and interconnected. Moreover,there is a growing trend for several operators to sharean access line, which is called “unbundling”. Therefore, it is important to make recommendations for
EMC, overvoltage, and safety based on international
decisions, so that no operators are at a disadvantage.
First of all, the telecommunication system configuration for multiple operators and relevant issues werediscussed. Recommendations for each item, whichFig. 2. Immunity recommendations should be revised because of theincreased risk of radio frequencies being used by nearby equipment.

Vol. 2 No. 9 Sep. 2004

Fig. 3. Radio base stations need to beprotected against lightning.

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Lightning
Telecom. center

A

Remote site

DInterference

B

B
AC

A

User building
MDF
B

A

A

A
A

Power
degradation

Surge protective
deviceCableCA
Cross-talk
CAC
Earthing
conditionCC

Repeater

MDF

Surge protective device

DC power feed
AC power feed
Signal line
Earth wire

Rectifier

A–D: network operators A–D
MDF: main distributing frame

Telecom. equipment
Radio equipment

Fig. 4. Co-location and unbundling.

should be referred to as requirements, were listed.
Regulations and corresponding procedures for colocation and unbundling were made into Recommendation K.58 and K.59, respectively.
The next study period is scheduled to discuss methods for evaluating electromagnetic environments andtheir effects and eliminating problems in co-locatedand unbundled conditions, including emission
requirements for broadband access systems used in
multiple systems existing on one cable, a methodology for distinguishing responsibilities for EMC trouble under co-located conditions, and a method for
installing different equipment in new access network
structures under unbundling conditions while meeting EMC, safety, and resistibility requirements.
4. Revision of the overvoltage and overcurrent
resistibility recommendations
Recommendations for resistibility to overvoltage
and overcurrent specify the degree to which telecommunication equipment should withstand overvoltage
and overcurrent caused by lightning discharges,
power induction, power contact, and so on. The basic
recommendation K.44, which provides a test method,introduces a test from one external port to another70

external port for unearthed equipment, an internal
port test, and conditions (termination) for untested
ports. Moreover, K.20, K.21, and K.45, which were
product family recommendations, were also revised.
However, many telecommunication ports are not covered by the test. Test methods and levels for recently
introduced telecommunication ports include USB(universal serial bus) and IEEE 1394 (also known as
FireWire, iLink, and Lynx). Moreover, in high-speed
networks such as those using digital subscriber lines,
the equipment is continuously connected and in operation. Since lightning surges will almost always beinduced in the equipment while it is operating, testingshould be performed under this condition. However,K.44 does not describe testing while equipment isoperating. The test requires a de-coupling network,
which can decrease the effect of lightning on auxiliary equipment and can handle high-speed communication such as xDSL or LAN. Discussion of test
devices is also scheduled.
Besides the abovementioned background, SG5 isscheduled to make recommendations or handbooksabout i) protection against electromagnetic environment effects for various equipment and devices covering various user conditions and service types and ii)
human safety from electrical hazards. Table 1 shows
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Table 1. List of recommendations revised or created during the 2000–2004 study period.
K.20

Resistibility of telecommunication equipment installed in a telecommunications centre to overvoltages andovercurrents

RevisedK.21

Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents

RevisedK.34

Classification of electromagnetic environmental conditions for telecommunication equipment—basic EMC
recommendation

RevisedK.43

Immunity requirements for telecommunication equipment

RevisedK.44

Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents—basicrecommendation

RevisedK.45

Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages andovercurrents

Revised

K.46

Protection of telecommunication lines using metallic symmetric conductors against lightning induced surges

RevisedK.48

EMC requirements for each telecommunication network equipment—product family recommendation

Revised

K.55

Overvoltage and overcurrent requirements for insulation displacement connectors (IDC) terminations

NewK.56

Protection of radio base stations against lightning discharges

New

K.57

Protection measures for radio base stations sited on power line towers

New

K.58

EMC, resistibility and safety requirements and procedures for co-located telecommunication installation

New

K.59

EMC, resistibility and safety requirements and procedures for connection to unbundled cables

New

K.60

Emission limits and test methods for telecommunication networks

NewK.61

Guidance to measurement and numerical prediction of electromagnetic fields for compliance with human
exposure limits for telecommunication installations

New

K.62

EMC prediction through mathematical modelling

New

K.63

Maintaining the suitability of production telecommunications equipment to its intended environment

New

K.64

Safe working practices for outside equipment installed in particular environments

New

Earthing & bonding handbook

NewHandbook

the recommendation list issued as a result of the discussion in the study period from 2000 to 2004.
5. Global environment
Global environmental conditions are being studied
so that equipment that conforms to the recommendations may be used in any country in the world. In particular, the earthing and power distribution systems inuser buildings differ from country to country. The
existing recommendation K.21 covers resistibility
against overvoltage and overcurrent for equipment
installed in a user building. It assumes that earthingand power distribution have a common bonding system*2 such as the TN system, which is covered by
K.31, because many European countries and theU.S.A. use it. Consequently, it is unwise to apply
K.21 resistibility specifications in countries that use
the TT distribution system (such as Japan) and IT distribution systems, because the probability of damage
from lightning will be higher. As a result, NTT uses a
different resistibility level [3].
SG5 previously recognized that when equipment isinstalled in IT or TT systems, there is a high probability of high voltage appearing between telecommuVol. 2 No. 9 Sep. 2004

nication line and power line if the telecommunicationand power line protection devices are not connected
together (i.e., if a double line does not exist in Fig. 5).
During the discussion of the revision of K.44, SG5
recognized that the same problem also exists forequipment installed in TN systems.
Methodologies for solving problems for user buildings in such a global environment were discussed andthree solutions were proposed: (1) improve earthing,(2) install additional overvoltage protection devices,and (3) specify a special resistibility level for cases
where the earth is not improved. SG5 is now discussing K.pcp (protection at customer premises) witha view to adopting special resistibility levels equiva*2 Common bonding systems: Systems for distributing commercialpower include TN-C, TN-S, and TN-CS, which are widely used inEurope and the United States, IT used in Northern Europe andother places, and TT used in Japan. The TT system supplies commercial electric power using two wires, one of which is groundedon the customer side of the transformer on the utility pole. In theIT system, neither of the two wires running to the customer fromthe utility pole’s transformer is grounded; instead, these wires areinsulated from earth. The power supply system is not grounded.
The TN system grounds the power supply system at one locationand features a protective earth conductor to ground the device tothat point when supplying power.

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Telecommunicationequipment
L1
Telecom.
lineee

L1

Overvoltage
appears

L2

w

q

N

AC mains

q–e: surge protective device (SPD)For TT or IT power distribution, SPDw is needed.
For TN-C,TN-S,or TN-CS, SPDw is not needed, because it is possible to connect
directly between N and earth.

Fig. 5. Global earthing environment and resistibility against overvoltage.
Table 2. List of questions during the 2000–2004 study period.
Title

Working party

1Resistibility, EMC and safety aspects of unbundling and interoperability in telecommunications networks

22

EMC related to broadband access systems

23Radio-frequency environmental characterization and health effects related to mobile equipment and radiosystems

24

Resistibility of new types of communication equipment and access networks

15

Lightning protection of fixed, mobile and wireless systems

16Bonding configurations and earthing of telecommunication systems in the global environment

17

EMC prediction through mathematical modelling

28Quality processes using electromagnetic compatibility

29Interference produced by power lines and electrified railway lines into telecommunications networks

110Methodology for solving electromagnetic problems in telecommunications installations

111

Maintenance and enhancement of existing recommendations related to human safety in thetelecommunications environment

112

Maintenance and enhancement of existing EMC recommendations

213

Maintenance and enhancement of existing resistibility recommendations

214

Terminology–lent to NTT’s technical requirements [3].
6. Future topics
As mentioned above, problems related to the electromagnetic environment will appear along with newtelecommunication services, new usage conditions,and so on. Therefore, it is important to keep discussing specifications that suit new electromagneticenvironments. And for human safety, it is necessary
to coordinate with IEC and WHO standards (IEC:International Electrotechnical Commission, WHO:
World Health Organization). Table 2 shows the list ofquestions studied in the period from 2000 to 2004.
All these questions will be studied in the next period
except for question 8, because K.63 has already been
provided and question 8 will be merged with question72

12. In addition, three more questions will be added:(a) Security of telecommunication and information
systems regarding electromagnetic environment(b) EMC requirements for the information society(c) Home networks
The reason for proposing question (a) is that information technology equipment is becoming important
as a basic infrastructure for society, and risks such as
cyber terrorism are increasing. Therefore, security
should be managed according to customer needs orservice levels. This question will cover electromagnetic threats involving malicious artificially induced
high-power transient phenomena and electromagnetic security involving information leaks from telecommunication networks via unexpected radio emission
from equipment. Mitigation techniques, such as
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shielding, and methods for evaluating protective measures will also be discussed. The EMC requirements
for ubiquitous and broadband systems will be discussed in question (b). For such equipment used inhome networks, the requirements will be discussed
based on research into the actual electromagnetic
environment in homes.
References
[1]
[2]
[3]

http://www.itu.int/ITU-T/studygroups/com05/index.asp
Technical requirement for immunity of telecommunications equipment (2nd edition), TR549001 May, 2002.
Technical requirements for resistibility of telecommunications equipment to overvoltage and overcurrent (1st edition), TR189001 Jan.,
2003.

Vol. 2 No. 9 Sep. 2004

Tetsuya Tominaga
Senior Research Engineer, NTT Energy andEnvironment Systems Laboratories.
He received the B.E. and M.E. degrees inmechanical engineering from Doshisha University, Kyoto in 1989 and 1991, respectively. He
joined NTT Telecommunication Networks Laboratories in 1991. He was engaged in R&D ofelectromagnetic compatibility for telecommunication systems. He has attended ITU-T SG5
since 2002 and he is the associate rapportuer ofQuestion 6/5 (bonding configurations and earthing of telecommunication systems in the globalenvironment). He is a member of IEEE, the Institute of Electronics, Information and Communication Engineers (IEICE) of Japan, and theRobotics Society of Japan.

Ryuichi Kobayashi
Technical Assistance & Support Center, NTT
East.
He received B.E.E. and M.E.E. degrees fromthe University of Electro-Communications,Chofu, Tokyo in 1991 and 1993, respectively. He
joined NTT Telecommunications Networks Laboratories in 1993 and is currently working tosolve EMC trouble in the field. He has attended
ITU-T SG5 since 1997 and he is the rapportuer ofQuestion 1/5 (Resistibility, EMC, and safety
aspects of unbundling and interoperability intelecommunications networks). His researchinterests are the area of measurement methods
for electromagnetic noise and electromagneticenvironments. He is a member of IEICE andIEEE.

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