Power lines carry Broadband data

Paul Boughton

Broadband over Power Lines (BPL) is something the electricity industry will be hearing much more of before long. It uses national grid networks to carry datacommunications and to access the internet. It is sometimes known as Power Line Communications (PLC) although that title generally refers to the data used by utilities to control the grid itself.

BPL works because standard ac electricity is transmitted at a frequency of 50 or 60Hz and the PLC control system operates below 500kHz. This leaves almost the entire frequency range of the line free for communications trafficso BPL communications are modulated up to radio frequencies.

The system brings the internet into homes and businesses along with their mains electricity. A BPL modem plugs into the mains socket for both signal and power connection. Alternativelya wireless link can be used between the modem and an extractor box mounted on the nearest electricity pole.

But wireless is known to be an insecure technology and can allow hackers with the right equipment to view data and possibly piggyback their own data on the bandwidth the customer is paying for. So encryption must used to prevent the interception of sensitive data by unauthorised personnel.

BPL is an ideal way to bring broadband access into areas where telephone companies only offer low speed services but systems face considerable technical problems.
Signals suffer a relatively high attenuation rate due to discontinuities such as tapstransformers and other devices connected to the system. There is also relatively high background noise on power lines.

But a signal that is strong enough to overcome these hurdles is also strong enough to radiate and interfere with existing radio users from amateur enthusiasts to the emergency services. And the height and long length of power lines makes them an excellent antenna.

One answer is to reduce the strength of the communication signaland then to use repeaters to boost the signal when it threatens to get lost in the electrical noise. Alternativelyfibre optic cable can be wrapped round the high voltage cableswhere noise and radiation are at their worstand signals transferred onto low voltage cable for local distribution. But that all costs money and is it difficult to avoid people using the system for free when everyone has access to the infrastructure.

To inject signals into the networkutilities use special coupling capacitors connected to the ac conductors or a form of current transformer to induce signals onto the conductors. Where power transformers heavily attenuate signalsboosters are used to push the signal through. Alternativelyrelay units carry signals round the transformer.

Standard decision

Now the concept has been proventhe key task is to agree a global transmission standard so any piece of equipment will work with any other. OPERAOpen PLC European Research Allianceis the EU’s main research organisation for the standardisation and use of PLC in Europe. It has been funded by the EU with 20 million. In the USa popular standard is HomePlugwhich offers 14Mbps data transfer rates. The Universal Powerline Association (UPA)an international association working to promote global standards and regulations in the market has just completed the first version of its Digital Home Standard high-speed powerline networking specification.

The IEEE is developing a standardIEEE P1901for BPL that will offer speeds over 100Mbps.

Jim MollenkopfCo-chair of the IEEE P1901 Working Groupsays there are notable BPL deployments in Hong Kongwhere Powercom operates a commercial BPL network and reports over 40 000 customers; in Cincinnatiwhere Current Communications and Cinergy operate a commercial network that passes a reported 50000 homes; Spanish utilities Ibredrola and Endesa both offer commercial BPL services; andin the largest BPL deployment announced to dateCurrent Communications will be deploying a BPL network covering two million homes supplied by Texan utility TXU Electric Delivery. Additionallythere are deployments in MexicoBrazilAustriaAustraliaSwedenFranceMalaysia and South Africa.

In TasmaniaAurora Energy Ptyhas launched a trial to test the commercial viability of BPL. Bryan HolterBusiness Analyst with the companysays it is working with Mitsubishi and is using its 200Mbit BPL equipment. The Mitsubishi BPL modems have both a RJ-11 telephone jack for direct VOIP services and an RJ-45 jack for broadband internet access.

The areas served by BPL consist of a mixture of underground and overhead distributionwith the aerial assets consisting of a mixture of aerial bundled cable and four wire overhead.

BPL services are being offered to customers throughout the low voltage (240V) distribution systemwhile the medium voltage (11 000V) distribution system is being used to provide backhaul to regional substations where signals are passed to an existing network fibre optic backbone.

Aurora is also working with the Australian Communications and Media Authority and representatives of various emergency services groups to deal with the potential of BPL interference. Holter says there have been no significant interference problems to date and this is not expected to be an issue for future BPL expansion. At the moment Aurora is providing both Voice over Internet (VOIP) and internet services but it is currently investigating the potential of offering a limited video-over-internet service as well.

To date customer interest in BPL and take-up of the BPL services offered have been excellentand the company is currently preparing a business case which would see a large scale expansion of the BPL network across Tasmania. As part of the commercial trial it is also investigating a variety of network monitoringcontrol and metering applications using BPL.

BPL hardware

On the hardware sideAmperion offers a wide range of BPL equipment including antennae. Its Griffin unit is the overhead BPL product that has been deployed on four different continents. It enables communications over the medium voltage utility network and delivers the signal to customers via standard WiFi.

The Griffin 1500 MV product line is the newest addition to the Amperion Connect BPL solution. This innovative product offers an array of new connectivity options with either one or two 802.11 radio systems and an optional amplifier and fibre port.

Shipped in a rugged NEMA 3R enclosurethe Griffin 1500 MV is designed to mount on utility poles and to connect to overhead power lines via an insulated inductive coupler.
The insulated couplers have been tested to meet and exceed exacting utility safety standards and are available with either 15KV or 25KV ratings.

Its radio link can be used either for backhaul to the internet or as a high speed Wireless Access Point (WAP) providing connectivity to customers.

With an optional second radioit can perform both functions simultaneously while generatingreceiving or repeating the BPL signal. It is also able to support speeds of up to 24Mbpswhich helps remove potential bottlenecks and provides network operators with higher speed of service options.

In a combined projectPlexeon LogisticsAmperion and Broadband Energy Networks have announced a package that offers utilities a comprehensive way to deploy a BPL infrastructure.

The basic package includes BPL network elementsproject managementengineeringtrainingRF and performance testinga set of enabled utility applicationsnetwork monitoringanalysesand final pilot reports.

A supplemental package enables a utility to explore applications and services enabled by BPLincluding utility applicationsbuilding automationand public safety and security.

Open system

PlusPower Line Ultimate Systemis an open flexible systemdesigned to provide a wide range of telecommunication services over power line grids. Current applications include internet accesstelephone communications and automatic meter reading.
Further applicationssuch as home automationmay also be implemented over the same infrastructure.

The system uses an advanced modem technology to achieve high data rates over noisy low voltage power lines. It also incorporates routing capabilities and sophisticated algorithms to optimise the use of the bandwidth provided by the PLC modem and offers a standard data rate of 2.5Mb/s at user level.

Other equipment includes the NtPlus home network termination unit that provides communication services from any electrical wall socket and the RpPlus repeater for long distance transmission.

Broadband data transmission

Power PLUS Communications AG is a German company active in BPL around Europe since 2001. It covers over 300 000 households with nearly 30 000 subscribers. The most significant rollouts are in Mannheim and Linz with others in Dresden and Hamelin.

Since last yearmany small cities such as Hatzenbuehl and Hassfurt that have no broadband access have adopted BPL.

Its second generation PLUS-System enables broadband data transmission on low (230/400V) and medium voltage (1 to 24kV) networks. Based on TCP/IP-Protocolit offers a widefuture-proof platform for internet accesstelephony and video transmission as well as for process control and security applications.

CenterPoint Energy and IBM are working together to explore BPL technology. CenterPoint Energy has opened a BPL technology centre at one of its facilities in Houston to examine uses of BPL technology for consumers as well as utility companies. This includes a pilot program to demonstrate the capabilities of BPL in the home to Houston-area consumers.

With so much impetus behind itBPL is set to become a standard way of life before very long.

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