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Power line communication technologies in smart grids Chapter 4 137

overhead lines are closely depend on the structural design of the line. Alumi-
num, galvanized steel copper, steel-cored aluminum and cadmium copper are
widely preferred as conductor materials in production of overhead cables.
The overhead cables may be exposed to several important problems such as
weather conditions (storm, lightning, etc.), voltage drop, unbalanced load
issues, impedance problems in networks, grounding problems and so on. These
problems may lead to crucial interferences for both NB and BB communication
systems. In addition, coupling schemes, characteristic features and connection
types of employed cables and branch types can affect performance of PLC tech-
nologies operating over overhead transmission lines. Various overhead cable
examples utilized in the transmission and distribution networks are listed in
Table 4.4.

4.4 PLC regulations and standards
This section introduces recent developed standards of HDR NB-PLC systems
for SG communications. These standards are considered as the second-
generation standards while the first generation ones covering LDR NB-PLC
systems were widely utilized by utilities. LonWorks (ISO/IEC 14908-3),
KNX (ISO/IEC 14543-4-5), CEBus (CEA-600.31), X10, Insteon, IEC
61334-5-1/2/4, AMR Turtle and TWACS are good examples for the first gen-
eration standards developed for the UNB-PLC systems [1, 17].
Several organizations and industrial alliances initiated studies for defining
new standards for next generation PLC systems that operate under 500 kHz fre-
quencies with high data rates. These PLC systems (referred as HDR NB-PLC
systems) utilize multicarrier communication methods as in the BB-PLC sys-
tems. The IEEE 1901 and ITU-T G.hn standards have been designed for these
HDR NB-PLC systems. There exist four private ITU-T recommendations and
IEEE 1901.2 standard for NB-PLC systems that are published at around the
2013. These standards can be summarized as follows.
l ITU-T G.9901 “Narrowband OFDM Power Line Communication
Transceivers-Power Spectral Density (PSD) Specification” [80]: This
recommendation defines several control parameters for spectral contents,
PSD related definitions (i.e., PSD mask requirements, PSD transmit levels,
PSD measurement methods). In addition, ITU-T G.9901 integrates PHY and
data link layer (DLL) specifications of ITU-T G.9902 (G.hnem), ITU-T
G.9903 (G3-PLC) and ITU-T G.9904 (PRIME).
l ITU-T G.9902 “Narrowband OFDM Power Line Communication
Transceivers for ITU-T G.hnem Networks” [81]: This recommendation
covers PHY and DLL specifications for NB-PLC systems operating over
AC and DC electric power lines under 500 kHz frequencies. It is generally
developed based on the G.9955 and G.9956 materials, and ITU-T G.9902
regularly references to recommendation G.9901.