Power line communications
Richard Barth
Richard.Barth@noaa.gov
Fri, 11 Oct 2002 13:42:10 -0400
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<META NAME="description" CONTENT=" EDITOR'S PAGE EMI: Unplugging Internet Access Recent deregulation of the European utility market has led some utility...">
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<h4 align="left"><b><font color="#000000" size="3" face="Times New Roman, Times, serif">EDITOR'S
PAGE</font></b></h4>
<h2 align="left"><b><FONT color="#000000" SIZE=5 FACE="Times New Roman, Times, serif">EMI:
Unplugging Internet Access</FONT></b></h2>
<p align="left"><font face="Times New Roman, Times, serif" size="3" color="#000000"><img src="/common/ssteward.jpg" width="95" height="121" align="right" vspace="1" hspace="8"></font><FONT color="#000000" SIZE=3 FACE="Times New Roman, Times, serif">Recent
deregulation of the European utility market has led some utility
providers to consider using their power lines to provide broadband
Internet access. This new service for residential areas provides
a means of diversifying offerings and increasing profits. EMC researchers
are finding, however, that in terms of interference, this new technology
is not a viable alternative to traditional telecom options.</FONT></p>
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<p align="left"><font color="#000000" size="3" face="Times New Roman, Times, serif">Power
line communications (PLC) use unshielded 230-V/50-Hz low-voltage
cables inside and outside of buildings for transmitting data rates
of megabits per second, according to Diethard Hansen of Euro EMC
Service in Switzerland. Hansen says such rates require that EMC-critical
radio-frequency levels be injected into mains.</font> </p>
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<DIV>
<p align="left"><FONT color="#000000" SIZE=3 FACE="Times New Roman, Times, serif">"Utility companies want
to use this new technology to provide value-added services to
clients in private homes or industry, such as fast Internet access
or relatively fast local-bus systems, simply by plugging anywhere
into the 50-Hz, 230-V mains," he explains.</FONT> </p>
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<DIV>
<p align="left"><FONT color="#000000" SIZE=3 FACE="Times New Roman, Times, serif">Hansen is chair of a
working group for Germany's regulatory agency, RegTP. System measurement
data are hard to get from utilities, but he has closely followed
field trials in the United Kingdom, Germany, Norway, and Switzerland.</FONT>
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<p align="left"><FONT color="#000000" SIZE=3 FACE="Times New Roman, Times, serif">Germany
now has regulations (NB 30) that control radiated emissions below
30 MHz in the short-wave user spectrum. These regulations were
implemented to protect sensitive military and government monitoring
and communication services. Hansen says the results of PLC field
trials throughout Europe have shown that injecting such signal
levels results in radiated emissions 20–40 dB above Germany's
limits.</FONT> </p>
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<p align="left"><FONT color="#000000" SIZE=3 FACE="Times New Roman, Times, serif">"Early field trials in
the United Kingdom, Germany, and Switzerland showed excessive
radiated emissions above NB 30 limits, which are about 20 dB more
relaxed than those required in the April 2000 version of the UK's
MPT 1570 regulation," he says.</FONT> </p>
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<p align="left"><FONT color="#000000" SIZE=3 FACE="Times New Roman, Times, serif">Unshielded
low-voltage distribution systems are not designed for communication
purposes such as symmetrical subscriber lines (x-DSL). He says
that issues such as impedance changes, longitudinal signal attenuation,
uncontrolled coupling, light switches, and time-dependent loads
present difficulties for evenly distributing RF within buildings.
In addition, EMI filters designed for blocking high-frequency
PLC signals in IT equipment, TV and video, and appliances also
make the use of PLC systems difficult.</FONT> </p>
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<DIV>
<p align="left"><FONT color="#000000" SIZE=3 FACE="Times New Roman, Times, serif">PLC technology would
certainly provide an attractive alternative to traditional Internet
access. However, the technology currently fails to meet the requirements
of the EMC Directive. And the few national standards that have
been developed do not sufficiently regulate this technology for
an international market. More work must be done to address critical
issues such as noise floor, signal-to-noise ratio, and the potential
interference with existing technologies such as local-area networks
and DSL.</FONT></p>
</DIV>
<div align="left"></div>
<p align="left"><b><font size="3" face="Times New Roman, Times, serif">Sherrie
Conroy, Editor</font></b> <a href="mailto:sherrie.conroy@cancom.com"><br>
<font size="3" face="Times New Roman, Times, serif">sherrie.conroy@cancom.com</font></a></p>
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