ZyXEL Communications PLA-470 V2 - V3.0.5 Przewodnik Instalacji Pobierz pdf (Strona 35)

Drawing a parallel to the PSTN (public switched telephony network) model of a

national telephone company, the electrical distribution network’s power plant is its

central office, supplying a distribution network that reaches all the way to the sub-

scriber. This network is built on a star architecture where each branch of the star is

the telephone wiring linking the subscriber to the central office.

In the PSTN network, the central office serves as a switch between the IP traffic

coming from subscribers’ modems in the 20 kHz to 1.1 MHz frequency band, and

classic telephone communications in the 300 to 3,300 kHz band. Interpreted under

a network model, the central office acts as an Ethernet switch and IP router to the

high bandwidth link with the IP backbone (see Figure 2.1).

For example, in the French electrical distribution network, it is the MV/LV

transformer that links the MT network and the distribution networks, each serving

an average of 200 EDF subscriber meters (see Figure 2.2). The MV/LV transformer

can be viewed as the Ethernet hub of the EGS network and the gateway to the IP

backbone, on the basis of its high bandwidth IP transport links.

16 Architecture

Table 2.1 Levels of Electrical Voltage

Current name Traditional name (still in use) Common voltage levels in France

Ultra high voltage

400,000V

225,000V

High voltage

90,000V

65,000V

Medium voltage 20,000V

Low voltage

380V (three phase)

220V (single phase)

Figure 2.1 Simplified architecture of a PSTN (public switched telephony network)

1 2 ... 30 31 32 33 34 35 36 37 38 39 40 ... 348 349

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ZyXEL Communications PLA-470 V2 - V3.0.5 Przewodnik Instalacji Strona 35