PLC is an acronym for Power Line Communication, in other words, communication via the power lines used for power transmission
Since the power line is already installed, no additional cables or wires are required for data communication and it is precisely this aspect that makes PLC such an attractive proposition because no expenditure is involved in terms of the data lines. In some countries, power line communication (PLC) is used as the main communication channel between the smart meter and the central utility. Power line communication is, however, only one of a number of possible communication channels available within the smart grids. Sub-distributor or transformer stations do not usually communicate via PLC. However, PLC is well suited for use on the so-called ‘last mile’, from the smart meter to the data concentrator. Depending on the region, it is possible to reach 80 - 85% of all households with standard power line data transfer. A certain problem arises if too many devices communicate via PLC, so an optional wireless connection will be required at all times. In the past, the modulation technique S-FSK (spread frequency shift keying) was often used for power line communication according to IEC 61334; nevertheless, it only allowed very low gross data transfer rates of 9.8 Kbps. The new Prime and G3 standards, as well as IEEE P1901.2 provide the ability to transfer data at up to 500 Kbps, whereby the faster processes also use another modulation technique. Therefore in new power line designs, the new Prime and G3 standards, as well as IEEE P1901.2, are used to make a sufficiently high bandwidth of data transfer available to the systems.
In some cases, optical transmission technology is used for communications
Optical transmission technology can play to its strengths, not just when it comes to the transfer of high data rates in environments with strong electromagnetic fields. The transfer is either carried out using fibre optic cable, or cable that contains a polymer fibre (POF – plastic optical fibre) as a light conductor. For communications between the transformer and switching station, fibre optic connections are used, depending on the application.
The general problem is the unique authentication of the devices, because after all, each meter transmits relevant data to the energy supplier
An intelligent building has four main energy meters for water, electricity, gas and maybe also a heating energy meter. In a multi-occupation building, the corresponding meters are therefore available for each housing unit. A French study has calculated that in this way, worldwide, they alone would account for 1.7 billion network nodes on the Smart Grid. The general problem is the unique authentication of the devices, because after all, each meter transmits relevant data to the energy supplier. The energy supplier must rely on the fact that the transferred data is correct and that it also really does come from the exact energy meter or customer specified. For this reason, clear identification of the energy meter, as well as a secure transfer of data is required. In Germany, the BSI (German Federal Office for Security in Information Technology) laid down regulations that said (for electricity and gas meters), an RSA encryption with a key length of at least 1048 bits should be used in communications. The devices must be certified in accordance with EAL 4+, which is almost the same standard as that for a bank card. Different standards apply in other countries. In Belgium, for example, a pilot project has already been running for a year that utilises a chip. Although the chip has a high standard of security, it does not reach the EAL 4+ level that is required in Germany. CENELEC is working on an EU standard for smart grid information security.