IEEE EMC Society Standards Development Committee Withdraws as Cosponsor of IEEE BPL EMC Standard
Citing concerns about parts of its technical content, the IEEE EMC Society Standards Development Committee (SDCom) has voted to withdraw as the cosponsor of IEEE Standard for Power Line Communication Equipment -- Electromagnetic Compatibility (EMC) Requirements -- Testing and Measurement Methods (IEEE Standard 1775-2010). According to ARRL Laboratory Manager and BPL guru Ed Hare, W1RFI, this decision came about soon after the IEEE Standards Board approved publication of the standard over the technical concerns of the SDCom. Hare is an SDCom member and is a member of the IEEE Working Group that developed the standard.
Although it was a cosponsor of the standard, Hare said that SDCom had concerns about its technical content and tried unsuccessfully to influence the content throughout the development of the standard. Its last attempt was to provide comments into the IEEE ballot for the standard. These comments were detailed and specific to several areas of the standard, including strong criticism of the distance-extrapolation methods outlined in Annex A of the standard; the FCC is seeking to adopt the methodology in Annex A as regulation. The SDCom comments in their entirety are available are available on the SDCom web page here.
“SDCom represents broad-based expertise in the EMC field,” Hare explained. “It provided detailed and specific input to the standard working group, but the group consistently voted to reject this expert input. The result is a standard that is technically flawed and unsupportable by the former cosponsor of the standard.”
As one example, Hare noted that the standard contains a clause that stipulates that the BPL signal “shall be disabled” to make conducted emissions measurements of the device. To control EMC in the passband of the BPL signal, the standard requires that radiated emissions be measured; however, it allows the BPL signal to be turned off to measure the noise the BPL device conducts onto the ac mains. “This is not good engineering practice,” Hare said. “Testing this way will miss intermodulation, harmonics and any spurious signals that may be generated by the device only when it is in use. What industry would not like to be able to turn off its signals to measure whether those signals comply with standards or regulations?”
Hare said that SDCom also had concerns about the provisions in the standard to measure the way that field strength decays with distance near BPL systems: “The comments provided by SDCom outline several concerns that SDCom had with this material. This methodology has not been demonstrated to be accurate in a complex EMC environment. As just two examples, note the graphs shown below. The first, Figure 1, is a bird’s-eye-view of the H field from an overhead power line, from a method‐of‐moments calculation of an antenna model of an overhead line in Allentown, Pennsylvania, developed by the NTIA. Note that the way that field strength varies with distance at different points along the line varies tremendously from point to point, even being different in most cases on one side of the line than it is on the other. The premise that four points can be measured in this environment to determine the ‘real’ extrapolation is flawed.”
The SDCom comments also provided additional information that explained why four points measured laterally from a radiating power line cannot provide a reliable calculation of extrapolation. “The second figure below is from a graph provided to the FCC by Current Technologies, one of the BPL manufacturers,” Hare said. “It shows the measurements Current made of the field strength vs distance from an overhead power line. Note that one would obtain a different ‘real’ value for extrapolation from any four set of points chosen from these data.” The SDCom conclusion was that “[a] standard based on such a wildly varying set of results is insufficient and premature.”
In an explanation of the discussion that took place during the SDCom vote, SDCom Chairman, Andy Drozd noted that “[t]he vote on the motion reflects the SDCom’s professional opinion that the IEEE EMC Society’s long-standing reputation as experts in EMC would be placed at risk with the publication of the draft of the standard as it is currently written. Additionally, it is the SDCom’s opinion that by endorsing the publication of an ‘EMC Standard’ that does not adequately and sufficiently address important concerns expressed by experts of the EMC Society and in effect, contains certain technical flaws, will negatively serve the user community of this standard and could call into question the validity of the document as well as the integrity of the overall IEEE Standards process.”
Hare noted that the working group wanted to develop this standard as quickly as possible, rather than take the additional time to try to find resolution of the technical issues and questions put on the table by SDCom. “The end result of this is that the 1775 working group and other sponsoring IEEE societies have developed an EMC standard that does not have the support of the IEEE EMC Society sponsorship,” he said. “What is the value of that, and how can anyone rely on such a standard in confidence that it represents the best engineering practice that would normally be expected of an IEEE standard? There are some valuable and important aspects to this standard, but without the consensus that could have existed had the working group chosen not to set aside the technical input of the SDCom expertise, the process and end result have to be called into question.’