Direct current power delivery system and method

A method comprising:

• generating an alternating current (AC) component by a first unit, wherein the AC component indicates a status of the first unit;
• adding, by the first unit, the AC component to a high voltage direct current (HVDC) power line coupled between the first unit and a second unit;
• detecting, by the second unit, a presence or an absence of the added AC component in the HVDC power line;
• and
• determining the status of the first unit based on the added AC component.

A power transmission system comprising:

• a first unit for carrying out the steps of:
• transmitting high voltage direct current (HVDC) power on an HVDC power line;
• generating an alternating current (AC) component indicative of a status of the first unit;
• adding the AC component to the HVDC power line;
• a second unit for carrying out the steps of:
• receiving the HVDC power from the HVDC power line, wherein the HVDC power line is coupled between the first unit and the second unit;
• detecting a presence or an absence of the added AC component in the HVDC power line;
• and
• determining the status of the first unit based on the added AC component.