A Standard for Powerline Telecommunications Devices – the RSGB involvement
- The result of the second vote on a draft standard EN50561-1:2012 for Power Line Communication apparatus used in low-voltage installations has been announced. The standard was passed to be implemented by all European countries after the EU national standards organizations voted 19 for, 5 against with 9 abstentions; according to the weighted voting system used, this is recorded as 90% in favour of the standard, exceeding the 71% needed for adoption. This article explains some of the background to this decision.
For over 15 years the RSGB has been actively involved in the work to consider a suitable standard for powerline communications devices. Initially this work concerned “Access” PLT – the use of PLT technology to bring broadband into the home. When it became clear that Access PLT technology was not viable technically or commercially, attention shifted to PLAs – powerline adaptors, which carry broadband data around the home using mains wiring.
RSGB was responsible for forming an alliance of users of the HF spectrum who, working together in the late 90’s and early 2000’s successfully represented the need for caution in levels of emission from powerline devices. The RSGB and others were active in a number of forums considering PLT technology and standards, including a PLT workshop in Brussels in 2001 (at which the RSGB formally raised the issue of interference with PLT manufacturers), the Radiocommunications Agency Technical Working Group [1] , CEPT SE-35 committee [2], the ETSI-CENELEC Joint Working Group (which failed to reach a conclusion), the BSI GEL201/11 standards committee and more recently the CENELEC TC210 committee and Working Group 11 and visits to Brussels to discuss the concerns of radio users with the relevant part of the European Commission. The RSGB position has been consistent throughout all these discussions – that the HF spectrum is an irreplaceable resource, and that proper protection is needed to ensure that emission levels from PLT devices do not pollute the spectrum and make it unusable. In this we were helped by the Essential Requirements of the EU EMC Directive, which states “Equipment shall be so designed and manufactured …..as to ensure that the electromagnetic disturbance generated does not exceed the level above which radio and telecommunications equipment or other equipment cannot operate as intended”. The RSGB argued that an existing standard (EN55022) applied to PLA devices and represented a sensible level of emissions. The contrary view argued that EN55022 did not allow PLA devices to operate and so was inappropriate. In all these forums the problem was the conflicting requirements of PLT manufacturers for high power levels, and of radio users for low emissions.
As the discussions switched from “Access” PLT to in-house powerline adaptors it became clear that the use of “notches” in the emission spectrum of PLA devices might offer a degree of protection to amateur radio frequencies [3]. Notches were also being considered for other “critical” frequencies, such as aeronautical. But the RSGB view was that, whilst notches were helpful, the proposals under discussion would cause high levels of emission at most other frequencies in the HF spectrum.
In 2011, the IARU Region 1 EMC working group also took the view that the proposed draft standard was not appropriate and partly as a result of lobbying of national standards committees by IARU Member Societies, a vote on the standard was defeated.
When the standard was re-submitted for a vote in 2012, IARU Region 1 was less assertive, and a meeting of the EMC Working Group at Friedrichshafen took an ad-hoc vote that showed support for the standard (effectively the same standard it had opposed the previous year). Subsequently, some of those societies and others not represented at the vote, decided they were opposed to the draft, but by that time, there was no time for IARU Region 1 to take any coordinated action in support of protection of the HF spectrum. The RSGB was, for a time, almost a lone voice arguing that the draft standard was not appropriate and effectively was setting aside the EMC Directive’s Essential Requirements – something that only the European Parliament can do.
Our position was presented to the UK BSI committee along with other similar views from EMC Industry Association but failed to prevent the UK recording a positive vote on the draft standard. The RSGB technical argument is presented in detail elsewhere on the RSGB website ( PLT-PLA_Update-Draft-Standard-prEN50561-1_2012-Aug-2 )
We were informed that “regulatory and market surveillance bodies are generally unable to take enforcement action on the basis of EN 55022 alone, and that EN 50561-1 would offer realistic criteria on which such action could be based. With the present proliferation of low-quality PLT devices, it is obvious that this is in the public interest.” Apparently the broadcast interests “spoke tellingly of how they had to moderate and modify their positions in the face of technical evidence and market realities”. The Society concern here is that market surveillance in the UK and many other EU countries is ineffective. No action has been taken on PLA products coming onto the market which failed to meet the EN55022 standard by relying on withdrawn Standards, Committee draft papers that proposed higher emission levels. Ofcom’s commissioned report from ERA criticised this practice.
The RSGB protested the positive vote on the basis that “consensus was clearly not reached, with two members voting against and others abstaining at that meeting. We also believe that the wider public interest cannot be served by a standard that contravenes the Essential Requirements of the EMC Directive. The RSGB is not alone in its beliefs indeed at least 8 other European Amateur Radio organisations have opposed FpEN50561-1 at their standards organisations.” The disputes procedure of BSI was followed fully and resulted in BSI confirming that “the Chairman sought and obtained a degree of consensus (clearly not unanimity) such as to justify a positive vote.”
However we did achieve one extra concession “Noting the strength of your concerns, the Chairman of GEL/210/11 has agreed to our proposal to add a comment to CENELEC to the effect that, in the event of the publication of prEN 50561-1, we expect CLC/TC 210 to continue working on the standard with a view to the current emission levels specified in the standard being progressively reduced as technological development permits. The Chairman adds that if published the British National Committee will view this standard as an interim position.”
So in simple terms what does this mean? The standard has been approved and devices that fail to meet it will no longer be able to be sold, after a three-year grace period, unless certified to meet EN50561-2012. Significant protection is provided for the Amateur HF bands, as the standard specifies fixed notching for these and other safety of life bands, reducing conducted emissions from PLC devices to the levels of EN55022. The standard also requires a conformance test to confirm dynamic power control to limit the conducted emissions dependant on the insertion loss between the two communicating devices.
In the worst-case, emissions outside of the notch-protected bands could be 10,000 times higher than the previous standard EN55022. We remain concerned that at these levels inter-modulation effects produced when the devices are connected to the household mains could give rise to significant interference in the protected bands.
Weaker broadcast signals will be significantly affected outside the notch-protected bands as the weak signals received will most likely be at a low level, for which dynamic notching provides little protection. Dynamic notching protects strong broadcast signals when the received level at a given frequency exceeds a specified threshold.
How could the standard be modified to further reduce interference?
- Simply reduce the maximum conducted emissions allowed; this may reduce the maximum range and or bandwidth of the PLT devices in some extreme cases but alternative technologies exist to overcome these difficulties.
- Include in the standard the requirement to power down the devices after a specified idle time thus removing their pollution when they are not in use.
What happens next? It is not yet clear whether the standard will be published in the Official Journal of the EU. Only then will it be clear whether the standard brings with it a “presumption of conformity” with the EMC Directive Essential Requirements. The EU and CENELEC’s own EMC consultant has stated that it in his view it is in contravention to the Essential Requirements of the EMC directive.
One of the reasons why the combined voice of the amateur radio fraternity was not heeded was the absence of complaints reported by the national enforcement agencies. As a consequence it is imperative that interference cases are diagnosed and reported to, and pursued with, OFCOM when they occur [4]. The RSGB EMC committee is working with other parties to enable radio amateurs to do this and to build up statistics on the status of complaints. If a significant number of people are affected we can then lobby for further revision to the standard. If the devices do not cause publicised problems for our members then the protection provided by this new standard will be deemed adequate. We request you to help us by reporting cases of suspected PLT interference to OFCOM – and telling our EMC Committee too.
The RSGB will continue to work with other national radio associations to protect the HF radio spectrum and will continue to press Ofcom to put in place other measures to ensure compliance and to pursue interference from PLT apparatus is in use.
Dr John AV Rogers, M0JAV
Chairman RSGB EMC Committee
- www.ofcom.org.uk/static/archive/ra/topics/interference/documents/twg-finalreport.pdf
- www.erodocdb.dk/docs/doc98/Official/word/ECCRep024.doc
- www.rsgb.org/main/emc/video-demonstration-of-the-effects-of-pla.php
- http://rsgb.org/main/technical/emc/i-am-experiencing-interference/
Category: PLA-PLT
