![]() By comparison, the electronics to encode and decode is usually small, in a special purpose integrated circuit. Most of the expense of any PLC system is the power electronics. Power meters often use small transformers with linear amplifiers in the range of tens of watts. Utility companies use special coupling capacitors to connect radio transmitters and receivers to the AC power carrying conductors. Some meters switch into a higher billing rate when the "party switch" is flipped. To handle these cases, some equipment includes switches to circumvent load shedding. For example, during a party, a dangerous heat wave or when life-preserving medical equipment is on-site. Grids that use cogeneration can enable auxiliary customer equipment when the generators are being run to generate heat rather than electricity.Īn annoyance for customers is that sometimes the code to turn equipment on is lost, or load shedding is inconvenient or dangerous. Brownouts and rolling blackouts are more easily prevented. This lowers costs for electricity and fuel usage. In this way, the utility can avoid up to 20% of capital expenses for generating equipment. to set the clocks of the power meters at midnight. Often the decoder is part of a standard electricity meter, and controls relays. Equipment at a customer site receives the codes, and turns customer equipment off and on. Codes are sent by slowly turning the tone on and off. Each district usually has its own frequency, so that adjacent areas are unaffected. Typical frequencies are from 100 to 2400 Hz. Ripple control adds an audio-frequency tone to an AC line. ![]() Higher data rates generally imply shorter ranges a local area network operating at millions of bits per second may only cover one floor of an office building, but eliminates the need for installation of dedicated network cabling. Low-frequency (about 100–200 kHz) carriers impressed on high-voltage transmission lines may carry one or two analog voice circuits, or telemetry and control circuits with an equivalent data rate of a few hundred bits per second however, these circuits may be many miles long. is a notable exception, permitting limited-power wide-band signals to be injected into unshielded wiring, as long as the wiring is not designed to propagate radio waves in free space.ĭata rates and distance limits vary widely over many power-line communication standards. Some jurisdictions (such as the EU), regulate wire-line transmissions further. These jurisdictions usually require unlicensed uses to be below 500 kHz or in unlicensed radio bands. Many nations regulate unshielded wired emissions as if they were radio transmitters. The main issue determining the frequencies of power-line communication is laws to limit interference with radio services. The propagation problem is a limiting factor for each type of power-line communications. Since the power distribution system was originally intended for transmission of AC power at typical frequencies of 50 or 60 Hz, power wire circuits have only a limited ability to carry higher frequencies. Different types of power-line communications use different frequency bands. Power-line communications systems operate by adding a modulated carrier signal to the wiring system. Radio interference, for example, has long been a concern of amateur radio groups. Various data rates and frequencies are used in different situations.Ī number of difficult technical problems are common between wireless and power-line communication, notably those of spread spectrum radio signals operating in a crowded environment. Typically transformers prevent propagating the signal, which requires multiple technologies to form very large networks. ![]() Most PLC technologies limit themselves to one type of wires (such as premises wiring within a single building), but some can cross between two levels (for example, both the distribution network and premises wiring). Power-line communication (also known as power-line carrier), abbreviated as PLC, carries data on a conductor that is also used simultaneously for AC electric power transmission or electric power distribution to consumers.Ī wide range of power-line communication technologies are needed for different applications, ranging from home automation to Internet access which is often called broadband over power lines (BPL). ![]() For other schemes to deliver data and power over one cable, see Power over. ![]()
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