IEC/CISPR Threatens Radio Services by a Planned 18 dB Relaxation of PLT Disturbance Limits
CISPR is the Special International Committee on Radio Interference of the International Electrotechnical Commission IEC with central office in Geneva, Switzerland. It is concerned with the development of standards regarding electromagnetic interference and most of these are adopted by the European Union and many other countries. Disturbance limits for Power Line Telecommunications (PLT) systems are defined by the standard CISPR 22 and its European equivalent EN 55022 entitled "Information technology equipment - Radio disturbance characteristics - Limits and methods of measurement".
A PLT Project Team (PT) was formed in 2005 to produce an amendment to CISPR 22 to cover special requirements for PLT equipment and its first Committee Draft (CD) was issued in February 2008 (doc. CISPR/I/257/CD). However, the comments of 23 IEC members National Committees (NC) and the European Broadcasting Union (EBU) showed insufficient support for the selected approach (doc. CISPR/I/266A/CC) as only 6 NCs supported the draft: Belgium, France, Israel, Italy, Spain and Switzerland. Interestingly, the major European PLT technology providers, developers and manufacturers reside in 5 of these 6 countries.
8 NCs strongly opposed the draft - Australia, Austria, Cyprus, Denmark, Finland, South Africa, Sweden and the United States of America - and some well-founded comments revealed its true purpose: to camouflage an intended 18 dB relaxation of the present PLT disturbance limits by introducing a revised method of measurement with an estimated Longitudinal Conversion Loss (LCL) of 24 dB in contrast to 6 dB in CISPR 22:2005.
For the measurement of disturbance an Impedance Stabilization Network (ISN) is needed, which provides a known port termination impedance and a measurement port. The ISN is used to measure the common mode disturbances and it is built to mimic a network with a certain LCL value, which is the ratio of differential mode signal injected into a network to common mode signal resulting from the network imbalance. A higher value indicates a higher symmetry of the network and hence less common mode signals and less radiation. An ISN with LCL = 24 dB would mimic an almost perfectly symmetric network and effectively yield an 18 dB relaxation of the present limits, but as many NCs noted this value is unrealistically high and not representative for real power networks. Additional unrealistic presumptions inherent to the proposed method would even further increase the effective relaxation.
Some short excerpts out of 35 pages of NC comments are quoted as follows:
"... the use on the real Austrian electricity network of devices fulfilling the above CD cannot be considered as an adequate basis for the protection of radio communication systems ... CISPR/I/257/CD does use a model based on LCL assumption to describe Powerline network. This does not represent real Powerline network in Austria. Furthermore the value of 24dB is much too high ... "The 25 W common mode impedance ..." makes a not realistic presumption ..."
"... This CD does not wholly reflect the opinions and recommendations of the task group. Around half the task group expressed concern that the method and limits of the CD constitute a substantial relaxation of the CISPR 22 limits and is therefore unacceptable. However, the task group agreed to send the CD out, without prejudice, to test the opinions of the NCs, in order to expedite a way forward ... The Australian National Committee disagrees in principle with the use of the T-ISN method in this document ..."
"... CISPR S and CISPR Plenary instructed the CISPR I PT to prepare the amendment with the strict objective of providing the same protection for radio services as provided by the pesent published edition of CISPR22. This instruction seems not to have been followed ..."
"... DK is of the opinion that regardless of the measurements made, the LCL value of 24 dB will not protect radio services from PLT emissions. In the latest CISPR 22:2005, modified, the value is 6 dB using AMN ..."
"... Finnish NC disagree of using an LCL value of 24 dB for ISN: This value does not give the same level of protection of radio services as provided by CISPR 22 for other IT equipment. The proposal actually is a technology specific relaxation of EMC requirements for PLT products ..."
United Kingdom:
"... The British NC does not support the approach taken in this CD. We are of the view that this CD is misleading in that it hides the reality that PLT requires a relaxation in the emission limit. We recognise that this relaxation is required to allow PLT to have a signal to noise ratio necessary for its operation. The British NC does not believe the LCL approach is the appropriate way to characterise the interference potential of the power network ... The British NC is concerned to ensure that the potential for cumulative effects from multiple individual equipment possibly having an adverse effect on the HF noise floor is fully addressed ..."
"... The complicated measurement camouflages the real issue: a differential-mode relaxation of 18 dB for PLC ..."
"... The Swedish National Committee does not support this CD because we do not believe that LCL is suitable to access the disturbance impact of power lines, no supporting measurements are given to show that a relaxation of 18 dB would not give raise to serious radio interference and no mention is made of either passive or dynamic techniques which might justify relaxed limits ..."
"... PLT devices use the power mains for communication. Therefore, they have the same interference potential as any other power main connected device. Because PLT injects desired signals on the power mains is no justification to change the required emission control ..."
European Broadcasting Union (EBU):
"... The document is seeking a means of significantly relaxing the present limits to enable PLT systems to operate. This approach is not acceptable unless other factors are identified to compensate for such relaxations ... The LCL value of 24dB is not acceptable, as the field strength measurements work indicates that a much lower value is warranted ..."
It has to be noted that the latter concern of the British NC has been commented by the Secretary with the words "Rejected. UK NC should provide evidence there is an issue there". Cumulative effects of PLT of course are an issue and have been treated extensively by the NATO Research and Technology Organisation (RTO) in Technical Report TR-IST-050 "HF Interference, Procedures and Tools". The whole report is worth reading.
In June 2008 the project team issued a "Proposed Approach on EMC emission requirements for PLT" (doc. CISPR/I/269/DC) wherein it abandons the busted camouflage and declares:
"... there was deemed to be insufficient support for the selected approach and the group came up with an alternative approach based on 6dB ISN. The group recognized that the basic requirement that PLT be able to operate sets a basic limit on the wanted signal which effectively produces a need for somewhat higher limits than are given in CISPR 22 ... the PLT PT agreed that the level of Power Spectral Density implied by I/257/CD is necessary for the appropriate operation of the PLT systems ... The PLT PT proposes the use of an ISN with an LCL of 6 dB, as a compromise, in response to several NC comments ... Against this background the PLT PT proposes the specification of Average and Quasi Peak limits which comprise a nominal 18 dB relaxation on the mains port limit ... NCs are advised that the current measurement method specified in I/257/CD will produce somewhat different results than the voltage measurement ... this may produce a further relaxation ..."
In other words: LCL shall be decreased by 18 dB from 24 to 6 dB but at the same time disturbance limits shall be increased by 18 dB which yields the very same net relaxation of 18 dB as in draft I/257/CD. And 18 dB are not "somewhat" but much higher as they represent a power increase by a factor of 63 ! National Committee comments and suggestions on that proposal are requested by the Secretary CISPR/I by 15 August 2008 in order to allow the PLT project team to discuss the comments at its next meeting in Berlin on 8 - 9 September 2008. Then a revised committee draft will be distributed for comment by December 2008.
If this amendment would be realized as planned, the European standard EN 55022 would most likely be adapted as well as many other national standards and according to BNetzA, the German Federal Network Agency, the following consequences would arise:
This substantial relaxation would seriously threaten radio services operating on shortwave, especially the broadcasting and amateur radio service which already suffer from ever increasing interference. Without doubt PLT is a dirty technology which pollutes the electromagnetic wave spectrum as a precious and limited natural resource, simply because the mains is neither intended nor suited for carrying broadband HF signals. Thus relaxing PLT disturbance limits is like relaxing justified and necessary air pollution limits just because an industrial lobby calls for it.
"The primary aim of CISPR is the protection of radio services ..." - These are the introductory words of the CISPR strategic policy statement. But instead of asking which PLT limits are needed in order to protect radio services, CISPR only asks which limits are good for PLT and thus grossly violates its prime policy. In fact, the proposed approach would serve the PLT lobby and fill their needs while totally ignoring the disastrous impact on radio services, which is certainly not the way to go. As a serious standardization body, and if only for its own policy statement, CISPR is supposed not to push a dirty technology like PLT by specific relaxations. If PLT is not able to leave intact the whole electromagnetic wave spectrum - not just some small "notches" - for the intended use by radio services, then it is simply unsuited for deployment and should leave the field to smarter technologies like Wi-Fi or WiMAX, just to name two.
Finally, it should be clear that the adoption of such a standard with drastically relaxed PLT disturbance limits by any member of the International Telecommunication Union (ITU) would be an infringement of the Radio Regulations (RR) as part of a binding treaty which clearly state:
"S15.12 8 Administrations shall take all practicable and necessary steps to ensure that the operation of electrical apparatus or installations of any kind, including power and telecommunication distribution networks, but excluding equipment used for industrial, scientific and medical applications, does not cause harmful interference to a radiocommunication service and, in particular, to a radionavigation or any other safety service operating in accordance with the provisions of these Regulations."
This information paper is published on and distributed by email to a large number of amateur radio associations as well as organizations, companies, magazines and individuals concerned with radio. I urge all affected recipients to further circulate this information and to take any appropriate measures that could help to prevent the planned relaxation of PLT limits. These measures include protest notes and comments to the IEC/CISPR ( ) as well as to the IEC National Committees which can be found on the List of IEC members. In addition, administrations should be informed and sensitized and at the same time reminded of the binding status of the Radio Regulations. I herewith declare that I undertake this information campaign as an independent idividual for the sole purpose to support all radio services and without pursuing any other goals.
7 August 2008,
author and publisher:
Karl Fischer
Amateur Radio Station DJ5IL
Friedenstr. 42
75173 Pforzheim
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