|Study Report on Electromagnetic Interference between Electrical Equipment/Systems in the Frequency Range Below 150 kHz
|CLC TR 50627
|CLC/TC 205A - MAINS COMMUNICATING SYSTEMS
This Technical Report is based on two Study Reports of CLC/SC 205A, having been worked out by their Task Force EMI [1a][1b] and provides the results and findings of these documents. It was created with the help and input from a broad range of involved stakeholders: network operators, equipment manufacturers, universities, accredited test houses and consultants. Beside the actual standardization situation it reflects the current emission situation found in supply networks and installations and describes electromagnetic interference (EMI) cases from twelve countries; investigation and analysis of the latter show a wide range of different types of electrical devices to be considered as a source or a victim of related EMI. This Technical Report highlights the occurrence of high levels of non-intentional emissions (NIE) in the considered frequency range, including values up to and exceeding the standardized limits for intentional signals from mains communicating systems (MCS), which also implies a high potential to cause EMI to other electrical equipment. On the other hand, several types of equipment show susceptibility to related emissions, being insufficiently immune. The Technical Report addresses the following issues: – a number of different types of electrical equipment are generating such emissions and/or are susceptible, to such, thus representing EMI potential, as a source or a victim of such EMI; – the interaction of electrical equipment in a certain supply area respectively installation, with its complex and volatile impedance character, as having an additional EMI potential; that besides NIE from general electrical equipment and signals from MCS and technically being quite different from emissions; – the fact that besides the conducted interference also radiated interference from NIE or signals from MCS, through the magnetic H-field following to related currents on the mains, is to be considered, what is of some importance also for the interference-free operation of broadcast time-signal systems or electronic circuits controlled by such; – the ageing of electronic components in electric equipment, which causes increased emissions and EMI to other electrical equipment as a result of not showing the same EMC characteristics as before being placed on the market, therefore no longer being able to conform with EMC requirements; – the additional aspect of differential mode operation, which should be considered for related immunity and testing specifications. These findings confirm that EMI in this frequency range is not limited to single types of equipment like inverters or MCS; instead a more general electromagnetic compatibility (EMC) problem concerning a larger spectrum of electrical equipment is identified. Although a case-by-case mitigation of related EMI cases might be seen as appropriate, the increasing application of technologies and systems with related EMI potential requires a more general solution, through standardization, taking a balanced viewpoint of EMC and economics into account. With regard to the actual standardization situation, a review of the actual EMC and Product standards based on the reported results seems to be advisable. After initiating the work in CLC/SC 205A, the now ongoing work in IEC SC 77A, as well as the publication of a related Technical Report on testing electricity meters  by CLC/TC 13 and of the new Immunity testing standard EN 61000-4-19 , appear as right steps into the right direction but needing further, extended efforts. As stated on European as well as on international EMC standardization level, the availability of compatibility levels for the considered frequency range appears as a key-requirement for future considerations on setting related emission limits and immunity requirements in various standards. A fundamental basis for the co-existence of intentional signals from MCS and NIE needs to be found.