Power Line Communication Frequently Asked Questions
What makes power lines a cost-effective media for networking devices?
What kinds of applications can be enabled by communications over power lines?
What are the challenges associated with communicating over power lines?
What is Echelon's expertise in this area?
What should I consider in evaluating power line communication solutions?
What is a "switched-leg" circuit?
What makes power lines a cost-effective media for networking devices?
Power line communication uses existing power lines within a building, home, or a utility power grid to transmit data from one device to another. With a well-designed power line solution, devices can communicate using the existing wiring infrastructure, without rewiring or modification. This convenience makes power line communication one of the most cost-effective means for networking devices.
What kinds of applications can be enabled by communications over power lines?
Any electrical devices connected to the power line can be networked to communicate with each other. Two examples:
Smart grid electricity meters. Utilities can network all of their electricity meters and read them from a remote location (known as automated meter reading or AMR). A power line smart transceiver in the meter can also enable remote power disconnect/reconnect and detect meter tampering and unauthorized power consumption. Our power line technology has been widely deployed throughout Europe in 300 million meters, a number that is rapidly increasing in Europe and other regions around the world.
Networked home appliances: In-home devices — such as refrigerators, washer/dryers, AC/heating equipment, lighting and security systems, pool pumps, solar panels, and others — could be equipped to communicate with each other and with the local electricity meter. Utilities and consumers could use this capability to monitor and manage power consumption more effectively (demand side management), and thereby increase cost savings and convenience.
What are the challenges associated with communicating over power lines?
The quality of the communications signal depends on the number and type of devices using power at any given time, the wiring distance (not physical distance) between the transmitter and the receiver, and the wiring architecture or topology. Because power lines were designed to carry power, not data, it takes a very sophisticated transceiver to overcome these challenges. Read more about challenges to developing reliable power line communications technology.
What is Echelon's expertise in this area?
Echelon pioneered power line communication technology in the 1980s, and we continue to innovate in the field.
What should I consider in evaluating power line communication solutions?
Some key concerns for manufacturers wanting to include control networking features in their products:
Total cost and components. A good power line communications solution should be able to interoperate with external microcontrollers and include memory, filters, or amplifiers. The cost of implementing an appropriate power supply is also a very important.
Frequency spectrum and compliance. It’s important to ensure a common networking platform for products used around the world. As an example of what this means, in Europe, power line signaling is confined to the 9kHz – 148.5kHz. This spectrum is further divided in to bands:
A band: 9–95 kHz for electricity suppliers
B band: 95–125 kHz for consumer use without protocols
C band: 125–140 kHz for consumer use with the CENELEC protocol
D band: 140–48.5 kHz for consumer use without protocols
Above 148.5 kHz: power line communications prohibited
Using the C-band with CENELEC protocol for in-home communication ensures that only one device communicates at a time, thereby minimizing collisions and improving communication reliability. The B and D bands, although legal for in-home communication, are more prone to collisions and interference from other devices, so they are more suitable when used as alternatives when the C-band is blocked by noise. The complex timing and access algorithms mandated under CENELEC EN50065-1 is already implemented in Echelon power line transceivers.
Performance in the presence of noise. Electrically noisy appliances such as low-voltage halogen lamps, computers, printers, hair dryers, and other devices are everywhere. Some television sets induce very high levels of signal distortion that can make communications impossible for some solutions.
Special wiring requirements. Conditioning circuitry and other wiring modifications can necessitate the services of a professional electrician, which adds cost. Solutions that require phase couplers to ensure communication between sockets on different phases, or wiring modifications to support switched-leg circuits are examples (see What is a switched-leg circuit? below.). Our power line solution does not impose wiring restrictions.
Evaluation tools. It is best to evaluate a transceiver in a real-world environment, and our easy-to-use tools provide a very convenient means for testing performance of the transceiver and the network.
Documentation. Clear and comprehensive documentation that provides a detailed explanation of every stage of the design-in process and that includes recommendations on system architecture, power supplies, and coupling circuit design is very helpful in reducing development time and bringing a well-designed product to market quickly.
What is a switched-leg circuit?
A switched-leg circuit is a common wiring architecture for lamp switches in many parts of the world. In this architecture the neutral is routed through the ceiling lamp and there is no direct neutral connection at the switch.
In these circuits, an intelligent switch must be able to power its transceiver and communicate when the lamp switch ON — and power its transceiver and communicate when the lamp switch OFF but without lighting the bulb. It must also be low-cost (including the power supply) and small enough to fit into a typical junction box.