Page 140 - From Smart Grid to Internet of Energy

124 From smart grid to internet of energy

though the UNB PLC technologies have the advantage of very long operational
range (typically >150 km), these technologies suffer from low data rates. Even
though data rate of each link is very low in this group of PLC technologies, sys-
tems operating in this band can benefit several parallelization and addressing
methods to improve scalability. On the other hand, these solutions have been
employed by power utilities for more than 20 years in spite of being proprietary.

4.2.2 Narrowband PLC

NB PLC systems operate at frequencies between 3 and 500 kHz. These fre-
quency bands are covered by CENELEC from 3 to 148.5 kHz, by FCC from
10 to 490 kHz, by ARIB from 10 to 450 kHz and by Chinese band from 3 to
500 kHz. The frequency allocation schemes of the NB PLC systems are illus-
trated in Fig. 4.3. The CENELEC band, which is divided into four categories, is
characterized by EN 50065-1 in the EU [29]. The CENELEC-A band covers
frequencies from 3 to 95 kHz and this band is only allocated for the use of util-
ities. While differential mode voltage level of the signals between 9 and 95 kHz
frequency band is restricted to 134 dBμV, the power spectral density (PSD) is
limited to 120 dBμV/200 Hz [30]. The frequencies within 95–148.5 kHz are
reserved for end-user applications and are referred as CENELEC-B,
CENELEC-C and CENELEC-D bands as can be seen from the Fig. 4.3. The
CENELEC-B band covers 95–125 kHz frequency range, while CENELEC-C
band contains 125–140 kHz frequency range and devices operating on this band
should support carrier sense medium access/collision avoidance (CSMA/CA)
protocol. The other one, CENELEC-D, covers frequencies between 140 and
148.5 kHz.
Since no special regulation has been made for frequencies above 150 kHz,
EMC limits of the EN 55022 are principally adopted. Thanks to Directive 2004/
108/EC, manufacturers can evaluate EMC of devices according to European

FIG. 4.3 Several frequency bands for NB PLC systems.