The introduction of the Smart Grid on a mass scale requires robust and reliable communication services. In general, a combination of two communication systems is taking on the challenge: short range or mesh wireless and narrowband power line communication (N-PLC). Both systems face challenges when millions of devices send and receive information and each of them has its place in various deployment environments and regional regulatory climates.
The idea of using the AC mains for communications is not new. The concept of sending communication signals on the same pair of wires that are used for power distribution dates to patents from 1924 implementing "Carrier Transmission Over Power Circuits”. The simple carrier signaling evolved to using various modulation schemes that comprise N-PLC. Only in the last two decades, however, advancements in communications technology made N-PLC a commercially viable solution for large scale deployments.
Narrowband power line Communication (N-PLC) is generally defined as communication over power line that is typically operating in transmission frequencies of up to 500 kHz (as opposed to Broadband PLC that targets much higher bandwidth at shorter distances and operates over a much higher frequency band). Specifically, frequencies of 148.5 kHz and less have been recognized by Europe's CENELEC standards body
for use in N-PLC systems on a public utility’s power wires. Within this frequency range the resulting data rates are modest, ranging from 1Kbps to less than 100Kbps. These rates are appropriate for telemetry and control applications. In North America, Japan and China, the frequency range of up to 500 kHz are viable under local regulations for N-PLC and offers a reasonably wide communications bandwidth (up to above 300Kbps) and a broader range of applications can be considered.
In a power transmission and distribution system the conduit available to all nodes by definition is the power line. An N-PLC system that can provide reliable and cost effective data communication capabilities is an ideal and natural solution to grid communication needs. However, due to the characteristics of the power line noise environment, its changing conditions and variations in equipment and standards, communications over the power grid are difficult. To both reliably operate in this challenging environment and to successfully co-exist with previously installed equipment requires new approaches. This article focuses on the characteristics of PLC within this frequency range and presents the common communication techniques currently used within this band.