Current PLC Network Market

Currently, electric distribution networks have greater coverage than telephone and cable TV networks, reaching 95% of households. In other words, through the PLC system most people will have the possibility of connecting to the Internet. Since the services of these other types of networks are already available in offices and industries, the markets expected to benefit most are residential areas and small and middle-sized businesses. 

It should be born in mind that despite its smaller coverage, the existing telephone network reaches all social sectors that can afford service. Supply of low-cost VoIP services would thus be competitive in lower-income sectors, which would cease to be customers of the local phone company. 

High and very diverse expectations have been generated around PLC technology. Some emphasize the social value of exploiting this technology (pursuing equality in access to information technologies and promoting human development), while others are commercial.

The promise of coverage for economically non-viable geographical areas with highly scattered users or difficult access is the calling card of this technology with respect to social ends. (This concept applies to users with LV supply, since transmission to the distribution transformer at MV is not competitive compared to DSL, as explained later). The advantages of this technology are extensive, which encourages its development..

General operation principles

PLC technology is simply a set of transmission elements and systems which, based on a regular power transport and distribution infrastructure, can offer customers the regular services offered by telecommunications operators.

It is possible to attain speeds between 1 and 1.5 Mbps per user. This makes it possible to offer Internet, high-speed data transmission and even IP telephony services.

All that is needed is to condition the electrical distribution infrastructure so it can transmit two kinds of signals simultaneously without either of them being affected: a low-frequency signal (50 to 60 Hz) to distribute power and a high-frequency signal (1-Mhz band) to transmit data, both of them flowing through a copper pair.

The new network, now configured and conditioned, is called High Frequency Conditioned Power Network (HFCPN), allowing the simultaneous transmission of power and data.

Servers are installed in electrical substations (or local transformers), which are usually connected to the Internet through fiber optics. The network-level protocol is IP.

The power distribution network is basically composed  of three parts or sections: low, medium and high voltage. Only the low-voltage section is used, something known in telephony as the “last mile,”  or the section that connects households to the power substations (equivalent to the local switch in telephony).

Figure. Structure of elements to provide Internet over the power network.

Operation Scenarios

PLC (Power Line Communications), also known as Power Line Telecommunication (PLT) or Broadband over Powerline (BPL), is the technology that makes it possible to transmit video, voice and data over the power networks. It should also be understood that the existing cabling inside each residence or office is part of the power network.

PLC technology offers the creation of home networks and access to broadband Internet using the existing power cabling infrastructure, without the need to install a new one.

This infrastructure can be divided into two general scenarios. One uses the existing power cabling in a building, home or office to set up internal communications (In-home), while the other uses the low- and medium-voltage distribution lines of a power utility to offer broadband Internet service (Access) through them.

Before introducing concepts related to PLC, it is useful to provide a brief description of what is known as power distribution networks, which are divided into high-, medium- and low-voltage networks.

High-voltage power lines make up a transport network that carries power from the generators to the consumption centers (population centers and industries). Most high-voltage power lines are aerial, and the voltage values handled in these sections are in the neighborhood of hundreds of kilovolts, since these high voltages allow energy to be transported more efficiently. At consumption sites, such as cities, there are usually large transformation centers that convert this electrical power into lower voltage values, giving rise to a second network – the medium-voltage power network –, which usually handles values between 10 and 50 kilovolts.

Finally, a new transformation takes place so that households can be provided with electric power. Depending on the country, there are facilities in population centers, in buildings or underground, known as transformation centers, where power is transformed to 110/220 volts – the voltages typically used in households. This is what is known as low voltage.

In turn, the power networks can be divided conceptually into several sections from the power plant to the subscriber, as follows:

• A first medium-voltage section, between 15 and 50 Kv, from the power generator to the first step-up transformer
• A transport or high-voltage section, between 220 and 400 Kv, that carries power to the transport substation
• A medium-voltage section – 66 to 133 Kv – between the transport substation and the distribution substation
• Another medium-voltage section between 10 and 50 kV, from the distribution substation to the distribution center
• Finally, a low-voltage power line – between 110 and 400 volts – that distributes power inside urban centers for domestic, commercial and industrial use

Currently, the application zone for PLC technology is in the last two sections of the power network, namely the medium- and low-voltage sections.

This text is from the technical notebook on Aspects of PLC of PCC.I

Coordinator: Ms. Josefina Cano