1. Main PLC technologies

1.1 History of PLCs

PLC technology is not new in principle. As early as 1838, in England, Edward Davy proposed a solution for remotely measuring battery levels at remote sites on the telegraph system between London and Liverpool. In 1897, he presented the first patent (British Patent No. 24833) for a technique to remotely measure electricity network meters communicating over power cables.

Known as Ripple Control, the first PLC systems were developed and deployed on medium- and low-voltage power grids in 1950. At the time, the carrier frequency was between 100 Hz and 1 kHz. The aim was to establish mono-directional communications via control signals for remote switching on and off of public lighting, or for tariff changes. Producers and distributors of electrical...