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one direction, differential mode currents flow in opposite directions. Therefore,
the CM currents may cause important EMI problems. The level of radiated EMI
generated by the CM may be crucial if the length of radiating source is in the
level that can be compared with the wavelength of the transmitted signal. There-
fore, radiated emissions are critical only for the BB-PLC systems.

4.5.1 NB PLC regulations

As stated in Section 4.2, the NB-PLC systems exploit frequencies between 3
and 500 kHz. The European Norm (EN) 50065 that encouraged the advance
in both LDR and HDR NB-PLC was released by CENELEC in 1991 [29].
The EN 50056 characterizes transmission limits and procedures for measure-
ments in the range of 3–148.5 kHz frequencies, and it also defines four CEN-
ELEC bands. Frequency ranges and transmission limits of CENELEC bands are
illustrated in Fig. 4.13 according to the EN 50056. The transmission limits
should be taken into account by considering measurement procedures explained
in the EN 50065. While the CENELEC-A band is assigned for utilities, the
others are assigned for consumers. In addition, devices to be operated in
CENELEC-C band have to support CSMA/CA protocol that necessitates trans-
mission and carrier sensing process in the range of 131.5 and 133.5 kHz, 125 ms
minimum pausing period and 1 s maximum channel holding features [87, 90].
The EMC regulations for PLC emissions is arranged by the FCC Code of Fed-
eral Regulations, Title 47, Part 15 (47 CFR §15) in the United States [31].While
Section 15.3 clause (t) of [31] identifies “power linecarrier” systems,
Section 15.113 points out that power utilities can exploit 9–490 kHz band for
PLC systems without protection and interference. In Japan, the frequencies
between 10 and 450 kHz are assigned for PLC transmission by the ARIB. This
standard also explains transmission limits and related measurement methods [91].

FIG. 4.13 Signal transmission levels in CENELEC bands.