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ITU-T Study Group 5 (Study Period 2005 – 2008)
Summary of Last Meeting

Meeting Executive Summary

25 - 29 February 2008
SG15 Chairman: Roberto Pomponi



Overview of the sixth Study Group 5 meeting held in Geneva from 25-29 February 2008

The SG 5 meeting was attended by 61 delegates representing 36 ITU-T Members and Associates. The meeting considered a total of 16 contributions and 89 Temporary Documents.

The meeting was devoted to the preparation of the final drafts of the Questions for the next Study Period and to the preparation of new and revised Recommendations, Handbooks and Volumes of the Directives for consent or approval by SG 5.

Consent and approval of Recommendations

Consent was reached on 5 new Recommendations and on 9 revised Recommendations. SG 5 also approved the revision of 2 Recommendations under AAP. These Recommendations are shown in the following Table, whereas their summaries are reported in the Appendix of this Executive Summary.

 
Type Number Title Approval
New K.72 Protection of telecommunication lines using metallic conductors against lightning: Risk Management AAP
Approved
K.73 Shielding and bonding for cables between buildings
K.74 EMC, resistibility, safety requirements for home network devices
K.75 Classification of interface for application of standards on resistibility and safety of telecommunication equipment
K.76 EMC requirements for telecommunication equipment - performance at low frequencies (below150KHz)
Existing K.20 Resistibility of telecommunication equipment installed in a telecommunications centre to overvoltages and overcurrents
K.21 Resistibility of telecommunication equipment installed in customer premises to overvoltages and overcurrents
K.26 Protection of telecommunication lines against harmful effects from electric power and electrified railway lines
K.44 Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents – Basic Recommendation
K.45 Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages and overcurrents
K.46 Protection of telecommunication lines using metallic symmetric conductors against lightning-induced surges
K.47 Protection of telecommunication lines using metallic conductors against direct lightning discharges
K.58 EMC, resistibility and safety requirements and guidance for determining responsibility under co-located telecommunication installations
K.68 Management of electromagnetic interference on telecommunication systems due to power systems and operators' responsibilities
K.60 Emission levels and test methods for wire-line telecommunication networks in case of radio interference
K.61 Guidance to measurement and numerical prediction of electromagnetic fields for compliance with human exposure limits for telecommunication installations


Revision of Directives and Handbooks

The following revisions have been approved:
  • Volume V of the Directives: Inducing currents and voltages in power transmission and distribution systems.
  • Volume VI of the Directives: Danger, damage and disturbance.
  • The Handbook on 'Mitigation measures'.

K-series Terminology and Guide to use the ITU-T SG 5 Publications

SG 5 approved the revision of the following documents that will be published on the web:
  • K-series Terminology;
  • Volume VI of the Directives: Danger, damage and disturbance.
  • Guide to the use of ITU-T Publications produced by Study Group 5 aimed at achieving Electromagnetic Compatibility and Safety

Recommendations to be deleted

SG 5 also approved the deletion of the following Recommendations:
  • K.31, which has been included in Recommendation K.66 and in the new Recommendation K.bl, will be deleted at the end of the approval procedure of new Recommendation K.73 (K.bl);
  • K.33, which has been merged into the revision of Volume VI of the Directives approved by SG 5;
  • K.53, which has been merged into the revised Recommendation K.68, will be deleted at the end of the approval procedure of revised Recommendation K.68.

Questions for the next Study Period

SG 5 has approved the titles and wordings of the Questions that SG 5 would like to study during the next Study Period. These Questions are reported in TD 665 rev.2. Considering that in the future structure of Study Groups, there is one option which suggests to move Questions 3/6 and 5/6 to SG 5 (see TSAG TD 552 R2), SG 5 believes that the wording of Questions A/5 and G/5 should cover the field of application of the existing wording of Questions 3/6 and 5/6, excluding optical fibre cables.

Liaison statements

SG 5 approved to send the following liaison statements to inform:
  • ITU-T IPTV and Questions 21 and 22 of SG 16 on the results achieved under Question 8/5 'Home networks';
  • IEC TC 81 and CENELEC TC 81X on the approval procedure related to Recommendations on lightning protection (new K.72 and revision of K.46 and K.47);
  • IEC TC 108 on the approval procedure of the new Recommendation K.interface (K.75);
  • IEC SC 37A that the new Recommendation K.var could start the approval procedure in one of the next SG 5 meetings;
  • ITU-D SG 2 that the Guide to the use of ITU-T Publications produced by Study Group 5 aimed at achieving Electromagnetic Compatibility and Safety has been updated;
  • CIGRE and UIC that Volumes V and VI of the Directives have been revised;
  • TSAG and SG 6 on SG 5 Questions for the next Study Period.

Work Programme

The work programme was reviewed; for the next meeting (November 2008), 3 new and 3 revised Recommendations are expected to be ready for consent.

SG5 Meeting Schedule in the next Study Period (2009-2012)
  • The first SG5/WPs meeting: Geneva, 24-28 November 2008
  • The second SG 5/WPs meeting: Geneva, 12-16 October 2009
  • No intermediate meeting has been planned before the next SG 5 meeting.
Next Technical Session

SG 5 has agreed to hold a Technical Session on 'Injury to persons touching electrical and electronic equipment inside a structure due to lightning' during the November 2008 meeting. SG 5 has also invited the Rapporteur of Question 11/5, Mr. Philip Day (Telstra), to organize this Technical Session.

Key words

EMC, Resistibility, Safety, Home Network, Broadband services, Electromagnetic Fields (EMFs).

Appendix - Summaries of consent and approved Recommendations

K.20 - Resistibility of telecommunication equipment installed in a telecommunications centre to overvoltages and overcurrents.

This Recommendation specifies resistibility requirements and test procedures for telecommunication equipment that is installed in a Telecommunication Centre.
Overvoltages or overcurrents covered by this Recommendation include surges due to lightning on or near the line plant, short‑term induction from adjacent a.c. power lines or railway systems, earth potential rise due to power faults, direct contacts between telecommunication lines and power lines and electrostatic discharges. The sources for overvoltages in internal lines, between equipment/racks, are mainly inductive coupling caused by lightning currents being conducted in nearby lightning strokes or lightning currents being conducted in nearby conductors.
Major changes compared with the 2003 version of this Recommendation include:
  • a revised power induction test where the basic and enhanced tests for both the inherent and the coordination test follow the curve in Figure 1.
  • removing the power induction test requirement for antenna ports where the installation is within the scope of K.71
  • addition of information on equipment included and excluded in scope
  • more clearly defined when the internal and external port classification applies to antenna ports
  • addition of external coaxial port test requirements
  • modification of internal port tests.
    • modification of symmetric pair cable port test. Shielded symmetric cable ports treated as unshielded cable ports and a test for multiple conductor interfaces added.
    • modification of internal coaxial cable port test. Surge applied directly to the inner conductor.
K.21 - Resistibility of telecommunciation equipment installed in customer premises to overvoltages and overcurrents.

This Recommendation specifies resistibility requirements and test procedures for telecommunication equipment which is installed in or on a customer premises building.
Overvoltages or overcurrents covered by this Recommendation include surges due to lightning on or near the line plant, short-term induction from adjacent a.c. power lines or railway systems, earth potential rise due to power faults, direct contacts between telecommunication lines and power lines and electrostatic discharges. The sources for overvoltages in internal lines are mainly inductive coupling caused by lightning currents being conducted in nearby lightning strokes or lightning currents being conducted in nearby conductors.

Major changes compared with the 2003 version of this Recommendation include:
  • removing the power induction test requirement for antenna ports where the installation is within the scope of K.71
  • a revised power induction test where the basic and enhanced tests for both the inherent and the coordination test follow the curve in Figure 1.
  • removing the power induction test requirement for antenna ports where the installation is within the scope of K.71addition of information on equipment included and excluded in scope
  • more clearly defined when the internal and external port classification applies to antenna ports
  • addition of external coaxial port test requirements
  • modification of internal port tests.
    • modification of symmetric pair cable port test. Shielded symmetric cable ports treated as unshielded cable ports and a test for multiple conductor interfaces added.
    • modification of internal coaxial cable port test. Surge applied directly to the inner conductor.
K.26 - Protection of telecommunication lines against harmful effects from electric power and electrified railway lines

This Recommendation reports the titles of the nine Volumes of the Directives published in 1988. The revision of Volumes V and VI of the Directives has required that this Recommendation be updated.

K.44 - Resistibility tests for telecommunication equipment exposed to overvoltages and overcurrents-Basic Recommendation.

This Recommendation seeks to establish fundamental test methods and criteria for the resistibility of telecommunication equipment to overvoltages and overcurrents.
Overvoltages or overcurrents covered by this Recommendation include surges due to lightning on or near the line plant, short-term induction of alternating voltages from adjacent electric power lines or electrified railway systems, earth potential rise due to power faults, and direct contacts between telecommunication lines and power lines.

Major changes compared with the 2003 version of this Recommendation include:
  • the addition of substantial information and schematics relating to decoupling, terminating and coupling to ground of associated;
  • all shielded ports now tested as unshielded ports.
  • added schematics for external coaxial cable ports.
  • the introduction of an internal port to internal port test;
  • the addition of tolerances for the power induction and power contact tests.
K.45 - Resistibility of telecommunication equipment installed in the access and trunk networks to overvoltages and overcurrents.

This Recommendation specifies resistibility requirements and test procedures for telecommunication equipment installed between Telecommunication Centres and between a Telecommunication Centre and Customer's premises building.
Overvoltages or overcurrents covered by this Recommendation include surges due to lightning on or near the line plant, short-term induction from adjacent a.c. power lines or railway systems, earth potential rise due to power faults, direct contacts between telecommunication lines and power lines and electrostatic discharges.

Major changes compared with the 2003 version of this Recommendation include:
  • a revised power induction test where the basic and enhanced tests for both the inherent and the coordination test follow the curve in Figure 1.
  • removing the power induction test requirement for antenna ports where the installation is within the scope of K.71
  • more clearly defined when the internal and external port classification applies to antenna ports
  • addition of external coaxial port test requirement
K.46 - Protection of telecommunication lines using metallic symmetric conductors against lightning-induced surges.

This Recommendation specifies a procedure to protect the telecommunication lines using metallic symmetric conductors against the overvoltages and overcurrents imposed on the lines due to nearby lightning discharges. The protection procedure is related to the exposure of the line to the effects of nearby lightning discharges, and includes the earthing and bonding of the cable shield and the installation of surge protective devices (SPD).
This Recommendation follows the risk management procedure which requires that the expected risk of damage due to both direct flashes and flashes near a telecommunication line shall be not greater than the tolerable risk. The user shall refer to Recommendation K.72 (K.risk) for the risk management procedure.
The risk assessment is limited to failure of insulation of telecommunication lines (buried or aerial cables, shielded or unshielded cables) which can cause the loss of service.
The user shall refer to Recommendation K.47 for evaluating the expected risk of damage due to direct lightning discharges, either to the line itself or to the structures where the line enters, and, if necessary, in order to select the protection measures to reduce the risk of damage due to direct flashes.
Examples of application of this Recommendation are reported in Appendix IV.

K.47 - Protection of telecommunication lines using metallic conductors against direct lightning discharges.

This Recommendation specifies a procedure for the protection of telecommunication lines using metallic conductors against direct lightning discharges to the line itself or to structures that the line enters. The protection procedure is related to the exposure of the line to direct lightning discharges and includes the selection of cable characteristics/installation, bonding/earthing of the cable shield, use of shield wires, lightning protective cable, steel tube, lightning protective cable duct, installation of surge protective devices (SPD) and route redundancy.
Examples of application of this Recommendation are reported in Appendix III.

K.58 - EMC, resistibility and safety requirements  and guidance for determining responsibility under co-located telecommunication installations.

With the liberalization of telecommunications, many services are provided by several Operators on the same cable. Equipment owned by different Operators is installed in the same telecommunication facilities and in many cases are interconnected. Therefore, problems related to EMC, resistibility and safety can occur.

This Recommendation describes necessary steps to ensure safe and problem-free operation in multiple Operator environments from EMC, resistibility and safety point of view.

This Recommendation gives also guidance for determining responsibility of EMC problems under co-location telecommunication installations.

K.60 - Emission levels and test methods for wire-line telecommunication networks in case of radio interference.

The deployment of broadband services fundamentally changes the utilisation of the telecommunication network. First, the transmission is present on the network at all times (‘always-on’). Second, the transmission frequency range employed is much greater than for previous access systems. Hence, the risk of interference with radio services has increased. In case of interference, the share of responsibility between the network operator and the National responsible body as well as the levels of the radiated field are not clearly defined.
The purpose of this Recommendation is to propose a measurement method and target levels to be used in case of interference with radio services. In addition, a methodology for solving the interference's case is mentioned, and under what circumstances the case has to be forwarded to the National responsible body.

K.61 - Guidance to measurement and numerical prediction of electromagnetic fields for compliance with human exposure limits for telecommunication installations.

This Recommendation helps telecommunication operators to verify compliance with exposure standards promulgated by local or national authorities. This Recommendation gives guidance on measurement methods that can be used to achieve a compliance assessment. It also provides guidance on the selection of numerical methods suitable for exposure prediction in various situations.

K.68 - Management of electromagnetic interference on telecommunication systems due to power systems and operators' responsibilities.

This Recommendation deals with the management of electromagnetic (e.m.) interference produced by electric power systems and electrified traction systems on telecommunication systems.
This Recommendation defines the procedure to evaluate the acceptability of an e.m. interference and gives:

  • the criteria defining the interference situations to be examined;
  • the interference management voltages to be applied;
  • the installation conditions of electric power, electrified traction and telecommunication systems under which the management voltages are applicable.
This Recommendation establishes an official agreement between telecommunication operators and power and railway operators in order to clearly share responsibilities, and, as a consequence, if necessary, the relevant expenses for mitigation measures.

K.72 (K.risk) - Protection of telecommunication lines using metallic conductors against lightning: Risk Management.

This Recommendation gives the methodology for evaluating the need of protection measures against lightning of telecommunication network using metallic conductors.

This method is based on the risk assessment: protection measures are necessary when the risk is greater than the tolerable risk. Maximum value of the tolerable risks is suggested.

The Recommendation considers the risk of loss of service of the telecommunication network.

The risk is evaluated through the risk components caused by lightning, which is the source of damage on telecommunication line as function of the striking point respect to the telecommunication line (lightning flashes direct to the line, near the line or direct to the structures connected at the ends of the line).

This Recommendation shall be used together with Recommendation K.47, which provides the risk assessment and the protection measures against lightning flashes direct to telecommunication line and to structures connected at the ends of telecommunication line, and Recommendation K.46, which provides the risk assessment and the protection measures against lightning flashes near the telecommunication line.

K.73 (K.bl) - Shielding and bonding for cables between buildings.

Bonding and earthing of telecommunication installations is done for reliability and personnel safety reasons. The evolution of the power architecture of telecommunication systems has created new installation conditions for equipment. To cover these situations, bonding and earthing configurations need to be defined that ensure adequate reliability and safety are maintained.
This Recommendation analyses the situation in which the equipments, connected together, are installed in different buildings with different earthing and power feeding conditions.

Also this Recommendation includes installation requirements for equipment located in different buildings, having the same earthing and feeding power conditions, to improve the shielding and bonding of telecommunication and power cable between buildings.

Other recommendations dealing with bonding and earthing are K.27 (Bonding configurations and earthing inside a telecommunication building), K.35 (Bonding configurations and earthing at remote electronic sites) and K.66 (Protection of customer premises from overvoltages). These recommendations do not cover how equipment installed in these different environments can be interconnected.

K.74 (K.hnw) - EMC, resistibility, safety requirements for home network devices.

With spreading use of the Internet, a network has been constructed in customer premises. Many wired / wireless telecommunication technologies also have been introduced in the home and devices that use these technologies have been used in close proximity each other. This situation may produce new types of EMC, Safety and Resistibility problems

This Recommendation provides EMC, Resistibility and Safety requirements for home network devices. There are many kind of equipment that may be connected to home networks. This Recommendation intends to give necessary requirements for home network devices that mainly have the function of telecommunication.

K.75 (K.interface) - Classification of interface for application of standards on resistibility and safety of telecommunication equipment.

This Recommendation provides guidance to manufacturers, network operators and test houses on the classification of the type of interface i.e. external (subjected to a.c. surges or conducted lightning surges) or internal (subjected to short fall-time transients induced into building cabling).
This Recommendation defines telecommunication overvoltage categories as a function of the inherent resistibility voltage of the equipment port or interface. For each category, the impulse withstand voltage between the telecommunication interface and person or hazardous circuit have been defined (peak value and waveshape).

These peak values and waveshapes should be suitable for insulation coordination purposes.

K.76 (K.low) - EMC requirements for telecommunication equipment - performance at low frequencies (below150KHz).

This Recommendation deals with the emission requirements from telecommunications networks equipment at frequencies below 150 kHz; the immunity requirements for telecommunication networks equipment, in particular with analogue voice interface, to signals at frequencies below 150 kHz are also defined.

 

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