Power line carrier has been used in DC lines since quite a long time ago. In the late 80’s, DIMAT PLC equipment were installed and commissioned in a 600 km link, where 40km were undersea, between the southern and the northern island of New Zealand.
The reason for using direct current technology in HV lines (HVDC) was based on the fact that it was needed to cover a very long distance, and that the capacitance effects between the line and earth could affect the transmission in alternating current line. This effect could produce also losses in the resistance of the conductor, which could be considerable and have a diminution of the useful power delivered.
For short transmission lines, that effect is minimum. But in the case of the 600 km line in New Zealand, they chose the HVDC lines in order to minimize the losses and to deliver as much useful power as possible. The DC line only requires two conductors (positive and negative) and hence a much simpler structure. Although it is expensive to convert AC to DC power, it could be compensated with less losses and reduced costs in construction, furthermore when we are talking about a 600 km link. In the case of the link in New Zealand at that time they used the DIMAT PLC called DVZ. There were 3 systems installed: 2 of 80 W each and another of 40 W.
Whether we are using an HVAC line or HVDC line, DIMAT power line carriers can be used in both applications to transmit information.
