Can we match power and communications?

By Paul Grad, engineering writer

It looked like a great idea: using the existing powerlines as a communications medium, sending internet data alongside the power transmission.

Usually referred to as Broadband over Powerlines (BPL), or “access BPL”, the provision of high-speed internet access, voice over internet protocol (VoIP), and other broadband services to homes and businesses by using the existing medium voltage (MV) and low voltage (LV) powerlines has been seen, at first, as a very attractive proposition, especially in remote rural communities.

Nearly all homes and businesses, even those in remote rural areas, are served by powerlines. Using powerlines to deliver broadband services to those areas would avoid the expense of installing coaxial cables or optical fibre systems.

Since power is usually transmitted as AC at 50Hz or 60Hz, and BPL would be transmitted typically at frequencies in the 2MHz to 80MHz range, the two signals would not interfere with each other.

BPL technology promised much in principle, but after many trials around the world, power and telecommunications companies and internet service providers could not prove it could deliver the reach and bandwidth required for serving the consumer broadband market in a cost-effective manner. Trials of access BPL technology have been carried out in many countries, including the UK and Europe, the US, Australia, Egypt, Ghana, India, Indonesia, Malaysia, Bangladesh, the Philippines, Saudi Arabia, and South Africa.

Companies that have been very active in testing and marketing BPL systems and equipment include Corinex Communications Corporation (Canada; www.corinex.com), Current Technologies (Illinois; www.currenttech.net), Power Plus Communications (Germany; www.ppc-ag.de), and Inovatech (London; www.inovatech-powerline.com).

The main outcome of those trials was that BPL technology could not match the reach and bandwidth of ADSL, wi-fi, and 3G mobile broadband services.

Low voltage or medium voltage is used for BPL, because high voltage lines are not suitable for the transmission of information. The signal does not propagate far enough at high bandwidth to be useful, and the costs of the labour and equipment to couple them make service provision uneconomic.

Most of the BPL networks in the US use medium voltage lines for backhaul as their power system is designed to use many small transformers on street poles servicing one to five customers. Australia and Europe use much larger transformers servicing dozens or hundreds of homes with most customers up to 400m from the distribution transformer.

Transformers are effective filters of the BPL signal, so it is necessary to construct a bridge around a transformer if you want to carry signal from the medium voltage to the 240V side. This way, both sides can use the full spectrum as the signal does not pass through the transformer. The signal is usually regenerated by a modem. However, the more common architecture in Australia and Europe is to inject the signal onto an electrical feeder cable running down the street somewhere between the distribution transformer and the customer’s property boundary. The injection point is connected to a fibre or wireless backhaul, which connects to the service provider’s office or telephone exchange.

After a while, the signal travelling along the medium-voltage line degrades, and repeaters have to be installed on the lines. The repeaters amplify and retransmit the data. Repeaters are installed typically every 300m to 700m along the medium-voltage line.

Repeaters increase cost. If the network requires many repeaters, it is best to move the injection point closer to the customer if possible. This is one of the flexibilities of BPL – the injection point can be anywhere.

Another major issue with BPL is the possibility of RF interference with high frequency radio communications and broadcasting. BPL systems may use orthogonal frequency-division multiplexing (OFDM), which allows them to mitigate interference with specific radio services by not using certain frequencies for data transmission subcarriers.

Apparently nearly all BPL systems that had undergone successful testing and operation worldwide have shut down. The first Australian utility to trial the BPL technology was the Tasmanian electricity company Aurora Energy. Several other companies followed Aurora’s lead, including the Woomera Consortium group, Energy Australia of NSW, Melbourne-based SP AusNet (now AusNet Services), and Canberra-based Country Energy. Optus trialled Inovatech technology and other companies’ products with Integral Energy in Sydney.

Utilities are generally reluctant to explain why they decided to abandon BPL, at least for the time being. The former director of Inovatech William Jago said: “My assessment is BPL has been overtaken by advances in optical fibre and wireless communication. Our own experience is that the technology was not ready for mass deployment as it was too labour-intensive and too susceptible to electrical network noise to deliver high bandwidth reliably in large networks. Further development would be needed in devices such as couplings, meter bypasses and routers”.

A sticking point is the relationship between utilities and telecoms. Mr Jago said power network operators are focused on very long technology and financial cycles – often longer than 20 years. They focus on safety and reliability, he said.

He said telecoms work on cycles of three-to-five years. They focus on customer service and cutting edge technology, with the expectation they must recover their investment in one-and-a-half-to-three years and rebuild most of their network equipment within five years.

Those differences in culture are one of the reasons why telcos and power companies have not worked well together to create BPL networks, Mr Jago said.

While access BPL seems to be largely shelved for the time being, the associated technologies will continue to be used in smart metering and smart grid applications such as substation automation, and as “indoor BPL”. Power companies need metering data to operate their networks and collect revenue. They therefore buy from developers of metering networks.

It is also possible to use BPL with traditional telephone or cable broadband to bring internet access to all rooms in your home. You plug the Ethernet lead from your modem into a special adapter that fits into one of the power outlets. The home electricity circuit then takes the broadband to every room in the house as a high-frequency signal superimposed onto the power supply. This is especially useful where wireless internet access is impossible.

Power Plus Communications (PPC) has installed several smart metering systems where data is transported directly over the existing power grid.

The German utility Stadtwerke Düsseldorf (SWD) has successfully tested the smart meter gateways from PPC and the Robotron software.

PPC, in partnership with Siemens Infrastructure and Cities, also supplied a BPL metering system for the water supply for the city of Doha, Qatar. Mapping the network was very challenging. Meters could be either in the garden wall of a family home or high on the roof of a tower. Those rooftop meters, as many as 10 per building, have to operate in particularly harsh conditions. PPC installed the BPL infrastructure in a series of looped networks, so no outages were needed during the installation.

PPC said BPL was particularly suited to this project because it uses existing powerline infrastructures; unlike wireless solutions, it can reach and decode signals from clusters of devices in diverse and hard-to-reach locations; critical devices are installed in the substation rather than on customer premises; and installation in a meshed network could be achieved without down time.

Corinex has also successfully installed BPL systems. The company’s smart meter communication module is a BPL-enabled module designed for smart meters in utility deployments. Recently the company has tested its smart meter infrastructure with its new SmartGrid BPL concentrator in the Czech Republic.

Corinex’s manager marketing and communications Kimberly Bruce said: “Because of the data speeds achieved by BPL, this technology is uniquely scalable. An investment in a BPL smart meter infrastructure allows for flexibility as regulatory and energy management requirements change and expand. BPL will allow more security encryption, demand/load management; integration of fluctuating renewable energy sources, and embedded distributed intelligence for analytics at the substation level.”

According to people in the industry, indoor BPL remains a hot prospect. Millions of power-line adapters have been installed in various countries. The latest generation of powerline equipment offers theoretical bandwidth speeds of up to 500Mb/s.

The Coalition Government has promised to deliver fast and affordable broadband to all Australians. It said its plan to transform National Broadband Network (NBN) will see download speeds of between 25Mb/s and 100Mb/s by the end of 2016 and 50Mb/s to 100Mb/s by 2019. The rollout of the NBN will be complete by the end of 2019, it said.

The Coalition did not say whether BPL will be part of its plan.

It looks like Australian utilities and telcos have pretty much given up on access BPL, at least for the time being. Developing countries, however, including Bangladesh, India and Pakistan are still interested in the possibility of deploying access BPL.

Whether access BPL will again be seen as an attractive proposition may depend partly on technological advances.