ZyXEL Communications PLA-470 V2 - V3.0.5 Przewodnik Instalacji Pobierz pdf (Strona 187)

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Identify the areas of the electrical network where the PLC signal is not received

and the parts of the building connected to other electrical networks or through

various outlets revealing excessive cable lengths or subjected to too many dis-

turbances.

We’ll examine this topology choice again in Chapters 11 and 12.

Propagation of the PLC Signal

One of the recurrent problems with the PLC technology is the signal propagation

over electrical wirings. Since these wirings have a specific resistiveness, the signal

propagation is subjected to an attenuation proportional to the cable length.

The tests performed by PLC device manufacturers and telecommunications test

laboratories, as well as feedback from deployed PLC networks, are used to set some

Figures relating to the PLC signal propagation.

“Internal” cables are cables used in private electrical networks (i.e. in domestic,

professional, and industrial buildings). The signal attenuation according to the cable

length can be evaluated with the various measurements carried out on copper elec-

trical wirings of 1.5 and 2.5 mm diameters.

Figure 8.13 illustrates the results of these tests at three significant frequencies:

10 MHz, 20 MHz, and 30 MHz. We notice that the attenuation is higher for higher

frequencies of the 1 to 30-MHz band. Since the cable length of a domestic installa-

tion is 200m on average, the PLC signal attenuation allows for the maintaining of

data exchanges, since the devices use interfaces that are sensitive enough to receive

the signal.

“External” cables are cables that belong to the public electrical network of the

utility. These cables are of the three-phase LV or MV type and are either buried, and

168 Installation

Figure 8.13 PLC signal attenuation according to inside cable length

Table 8.8 Distance for PLC Signal Propagation over External Cables

PLC TECHNOLOGY

CABLE

TYPE

DISTANCE

TCP BIT

RATE (MBIT/S)

Oxance HomePlug Turbo (1.1) Buried 1,300m 3

Spidcom Buried 3,000m 3

1 2 ... 182 183 184 185 186 187 188 189 190 191 192 ... 348 349

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ZyXEL Communications PLA-470 V2 - V3.0.5 Przewodnik Instalacji Strona 187