NACE 05114

Abstract

<strong>Introduction</strong> <br>HVDC transmission is used to carry electrical energy over long distances or to interface two alternating current (AC) power systems that might not be synchronized. HVDC transmission can be performed using monopolar systems, which are typically earth-return systems, or bipolar wire-return systems. <br>In monopolar systems, power is transmitted through a metallic conductor in one direction; see Figure 1. (IG refers to current flow in the Earth). Monopolar earth return systems use the earth as a conductor, and they typically use the sea as the earth return because of its low resistance and its ability to conduct large currents for a sustained period of time. Continuous operation of monopolar HVDC transmission systems is prohibited in some countries.