What is Broadband over Powerline (BPL)?
BPL is an emerging technology that utilises existing electricity power lines for the transmission of broadband data. BPL is also known as power line telecommunications (PLT) or power line communications (PLC). Many countries have recognised the significant role that broadband access could play in promoting economic, social and cultural developments. BPL technology is becoming recognised as a potential contributor to improve broadband access to the general public.
There exists two main families of BPL families; known as:
Access BPL utilises the distribution network owned, operated or controlled by an electricity service provider as the means of broadband delivery to and from premises such as the home or office.
To realise the application of Access BPL, some understanding of the electricity distribution network is necessary. Figure 1 shows a typical Australian distribution network.
Figure 1: Electricity Distribution Network
The electricity distribution network begins at the power station with electricity at ‘high voltages’ (HV), typically 110 to 500 kiloVolt (kV) for long distance transmission on the transmission grid and/or 33-66kV for sub-transmission systems. Use of high voltages for long distance transmission reduces power losses.
For power to be useful in residential or commercial environments, the high voltage is reduced by transformers at primary substations to a ‘medium voltage’ (MV) level (typically 11kV or 22kV) for wider reticulation and then further reduced to 240/415V at the neighbourhood transformer for final distribution to individual households and businesses. The 240/415 Volt (V) reticulation segment is referred to as the ‘low voltage’ (LV) network. Neighbourhood transformers on the Australian network serve between 20 and 120 premises (typically around 50), however in some rural areas consumers will have a dedicated transformer serviced by a Single Wire Earth Return (SWER) high voltage line.
Access BPL can be categorised into the following groupings:
Low Voltage Access BPL
This utilises the low voltage segment of the electricity distribution network to distribute broadband data through out local vicinities. In this application, the BPL signal is usually inject at the low voltage side of the neighbourhood transformer, or at locations nearer to the customer’s premises such as at power poles running down a street. Communications distances of some 200 metres are generally achievable; however, the signal can cover longer distances if repeaters are use. The signal is blocked from reaching the MV segment of the electricity supply as the neighbourhood transformer is a poor conductor of radiofrequency energies. Connection back to the wider telecommunications network is generally achieved by way of cable, optic fibre, radio methods or medium voltage BPL techniques (see next paragraph).
Medium Voltage Access BPL
This can provide a method of connecting the low voltage access BPL system with the wider telecommunications network. As the neighbourhood transformer is a poor conductor of BPL signals, connection between the LV and MV lines is achieved by the installation of special couplers, or bridging circuits, across the transformer. MV lines have relatively stable transmission characteristics and this condition allows BPL signals to travel increased distances without repeaters.
Figure 2: Medium Voltage BPL
In addition to delivering broadband data, access BPL technology is being developed to also incorporate management of the electricity grid by way of:
- automated meter reading;
- automated outage detection;
- load management; and
- power quality monitoring.
Using access BPL technology to manage the electrical supply distribution network may offer potential benefits not currently available to power utilities in an economically feasible form.
In-house BPL utilises electric powerlines not owned, operated or controlled by an electricity service provider (such as electric wiring in a privately owned building) to convey broadband data to devices connected to these powerlines. The electrical sockets usually provide the access points to this communications path.
In-house BPL technologies are largely designed to provide short-distance communication solutions that compete with other existing in-home interconnection technologies such as wireless, infra-red digital access or dedicated local area network cables. Product applications include the networking or sharing of information technology resources, such as multiple computer and printers, and video streaming.