The present invention relates to a method and an arrangement for transmitting data via an electrical conductor of an electricity grid.
Powerline Communication (PLC) denotes the transmission of data via electrical conductors. In this case, electrical conductors, for example power lines in the building and access area, are simultaneously used for transmitting power and for transmitting data.
Application scenarios for PLC include the connection of households to the internet and home networks with data rates in the two-digit megabit range, but also measurement, control and regulatory applications in various environments, such as smart grid, or sensor applications in distribution substations.
For measurement, control and regulatory applications, low data rates are generally sufficient. Depending on the setting, however, particular demands on the safety and robustness of such an application may apply. Safety and robustness are critical criteria for the supply of power, for example, when a sensor function still needs to be ensured even if the system voltage fails. In addition, in may settings, low maintenance expenditure is important, for example in order to save costs.
In this context, there are a series of competing standards for communication on power lines, particularly for low voltage and medium voltage lines, which allow data transmission at low and medium data rates. Examples are Spread Frequency Shift Keying (S-FSK), Differential Code Shift Keying (DCSK), G3, PRIME and G.hnem. These standards use variously complex types of modulation in the longwave band, such as FSK, Spread-Spectrum or Orthogonal Frequency Division Multiplexing (OFDM). In Europe, these standards usually operate in what is known as the CENELEC band below 148.5 kHz and achieve data rates of up to 128 kbit/s, but usually the rates used are in the single-digit kilobit range. Corresponding systems are symmetrical at the physical level, that is to say that they usually have, per communication endpoint, a transmitter and a receiver in one unit, the transceiver. Transceivers communicate with one another via the channel that connects them. The power requirements for such systems based on the related art is typically a few tens of milliwatts. Low voltage lines allow power to be supplied directly from the system voltage, at least while said system voltage is applied. By contrast, medium voltage lines, in which the signal is often transported on the shield of the line, require power to be supplied externally, for example from batteries, these having a limited life and therefore meaning increased maintenance expenditure, however.
In addition, systems that are based on the cited standards require apparatuses with a high level of technical complexity, which needs to be implemented in appropriate chipsets, for example. Such chipsets require complex configuration and also a dedicated supply of power, which means that such solutions are of no interest at least for simple sensor applications.
In “Electronic Identification Systems for Asset Management”, Richard Mcwilliam discloses an overview of the possibility of direct load modulation over power lines.
US 2008/303344 A1 discloses a power line communication system. In this system, apparatuses are connected to a plurality of electrical power lines. A master apparatus is connected to one of these power lines.