Global Standardization Activities

Recent Activities of PLT Project Team inCISPR
Yoshiharu Akiyama†
Abstract
PLT (power line telecommunication) using signals in the range from 2 to 30 MHz provides broadband
communication over power lines. However, some radio communication services could be affected byelectromagnetic disturbances radiated from power lines used for PLT because power lines were notdesigned for high-frequency signal transmission. Therefore, a method of measuring disturbances emitted from PLT systems and numerical limits on such disturbances have been discussed in the PLT project
team (PLT-PT) of CISPR (International Special Committee on Radio Interference). This article describes
recent activities of the PLT-PT.

1. What is PLT?

2. History of PLT-PT

Power line telecommunication (PLT) uses high-frequency signals transmitted over power lines to provide broadband communication for access networks
and home networks. The frequency band of the signal
is from 2 to 30 MHz and the maximum transmission
rate is 200 Mbit/s. PLT has an advantage over othertelecommunication systems using metallic lines interms of setup cost because it uses power lines thatare already in place. However, the frequency band of
the signals overlaps with the channel frequency ofamateur radio, broadcast radio, etc., which could beaffected by electromagnetic disturbances radiatedfrom PLT systems. Although methods of measuring
such disturbances on telecommunication lines andnumerical limits on disturbances have been specified
in CISPR (International Special Committee on RadioInterference) standards, power lines are electricallyunbalanced, so disturbances are radiated more easily
from them than from telecommunication lines.
Therefore, PLT disturbance measurement methods
and limits are being discussed in CISPR’s power line
telecommunication project team (PLT-PT).

The first project team was established in 1999 anddiscussion began at once. However, the draft international standard was rejected by the voting because
typical electrical characteristics of the electricalinstallations in different regions were not sufficiently
considered in it. Since the standard was not publishedafter five years of discussion, the project team wasdisbanded according to the rules of the IEC (International Electrotechnical Commission). The proposal torestart discussions under a new project team wasapproved at the Shanghai meeting in 2004. The current project team had its first meeting in San Juan,
Puerto Rico, in June 2005. Since then, there havebeen four meetings up to and including the Paris
meeting in May 2006.
The organization of CISPR is shown in Fig. 1. Standardization of measurement methods and limits for
disturbances from information technology equipment
such as personal computers, telecommunicationequipment, and audio-visual equipment is the scopeof sub-committee I (SC-I) and CISPR22 has been
published. The standard for PLT is published as anamendment to CISPR22.
3. Work plan of PLT-PT† NTT Energy and Environment Systems Laboratories
Musashino-shi, 180-8585 Japan
Email: akiyama.yoshiharu@lab.ntt.co.jp

Vol. 4 No. 10 Oct. 2006

The latest work plan of the PLT-PT, which wasrevised and agreed in the Paris meeting this May, is73

Global Standardization Activities

IEC

International Electrotechnical Commission

CISPR

International Special Committee on Radio Interference* Specifies limits and measurement methods of electromagnetic disturbances emitted from electrical andelectronic equipment for the protection of radio services.

SC-A

Radio-interference measurements and statistical methodsSC-B

Interference related to effects of industrial, scientific, and medical radio-frequency apparatus on other (heavy)
industrial equipment, overhead power lines, high-voltage equipment, and electrical traction devices

SC-D

Effects of electromagnetic disturbances related to electrical/electronic equipment on vehicles and internalcombustion-engine-powered devices

SC-F

Interference related to household appliances tools, lighting equipment, and similar apparatus

SC-H

Limits for the protection of radio services

SC-I

Electromagnetic compatibility of information technology equipment, multimedia equipment, and radioreceivers
WG1

Methods of measurement and limits for radiation and immunity of broadcast receivers and associatedequipment (maintenance of CISPR13 and 20)

WG2

Methods of measurement and limits for emissions from multimedia equipment

WG3

Methods of measurement and limits for radiation and immunity of information technology equipment(maintenance of CISPR22 and 24)

WG4

Methods of measurement and limits for immunity of multimedia equipment

PLT-PT

Methods of measurement and limits of equipment for broadband telecommunication overpower lines

Fig. 1. Organization of CISPR.

shown in Fig. 2. The target date for publishing thestandard is the end of March 2008. Items to be investigated are divided into seven tasks. Consensus
among different countries is being obtained task bytask, and some tasks are being discussed in parallel toreduce the total time until the standard is published.
There are three typical electrical installations in use
in Europe, USA, and Japan. In task 1, the characteristics of each typical electrical installation intended tobe connected to PLT equipment are being investigated. The equipment and services that could be affected by the PLT signal are listed in task 2 for each
installation in task 1. The coupling paths of the disturbances to the equipment and the services shown inFig. 3 are also being investigated in task 2. The levelof protection currently provided by CISPR22 for theequipment and services listed in task 2 are being
assessed in task 3. Radiated and conducted limits forthe disturbances of each typical part of electricalinstallation when PLT is operating are assigned totask 4. Measurement methods and limits for compliance tests in laboratories are being developed in tasks
5 and 6. Finally, the number of limits will hopefully
be reduced by regrouping the typical PLT installations in task 7. If possible, the same limits will be74

specified for the three different typical electricalinstallations. Task 5 is being discussed in parallelwith task 3, and task 7 is being discussed in parallelwith tasks 3–6.
A document for comments, including the results oftask 1, was produced in the Brussels meeting this January and it was circulated to the National Committees(NCs) registered in SC-I. Comments from the NCs
were collected and discussed one by one at the Paris
meeting and the section of the document on typicalelectrical installation was categorized into 18 classes.
Thus, task 1 was completed. Task 2 is now inprogress.
4. Activities of Japanese National Committee
The Japanese NC contributed some documents
related to the configuration of electrical installationsin Japan for task 1 and a list of equipment and services that could be affected by PLT signals for task 2.
It also made the first proposal for a method of measuring radiated and conducted disturbances emitted
from PLT equipment and presented measurements ofelectrical characteristics e.g., impedance, transmission loss, and longitudinal conversion loss (LCL) ofNTT Technical Review

Global Standardization Activities

Task 1

Task 2

Task 3CompletedTask 4

On going
Task 5

Task 6

Task 7
Oct 2004

March 2008
Task 1: Describe typical electrical installations where it is intended to connect PLT equipment.
Task 2: For each typical part of electrical installations described in Task 1, identify the potential
disturbed services/equipment.
Task 3: For each service/equipment type listed in Task 2, assess the level of protection currently
provided by CISPR22.
Task 4: Set radiated and conducted limits for emissions of each typical part of electrical installation
when PLT is operating i.e., a part of PLT installation.
Task 5: For each typical part of PLT installation, develop a measuring method for testing PLT
equipment in the laboratory that predicts emission after installation.
Task 6: For each typical part of PLT installation, set limits for the laboratory tests of PLT equipment.
Task 7: Regroup the typical PLT parts into a smaller number of classes.

Fig. 2. Work plan overview.

Radiated coupling

Receiver(for example)

PLT equipment

Conducted couplingPower lineFig. 3. Coupling paths of disturbances.

power lines, which are necessary to develop a disturbance measuring method.

sions in the PLT-PT will be accelerated in response toconditions around the world.

5. Conclusion
Recent activities of the PLT-PT in CISPR weresummarized. Regarding the progress of the workplan, it is currently expected to be difficult to publish
the standard for PLT equipment on schedule by theend of March 2008. However, field trials of PLT havebeen performed to enable the start of PLT services inEurope and USA. The Japanese authorities will specify disturbance measurement methods and limits andrevise the radio regulations to permit the use of PLTequipment within Japan by the end of 2006. DiscusVol. 4 No. 10 Oct. 2006

Yoshiharu Akiyama
Senior Research Engineer, EMC Technology
Group, Energy Systems Project, NTT Energyand Environment Systems Laboratories.
He received the B.E. degree in communicationengineering from the University of Electro-Communications, Tokyo, in 1990. Since joining NTTin 1990, he has been researching electromagnetic compatibility (EMC) of broadband communication such as wireless LANs, DSL (digital subscriber line), and PLT.

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