Study on reduction in electric field, charged voltage, ion current and ion density under HVDC transmission lines by parallel shield wires

Several models of shield wire were tested with the Shiobara HVDC (high-voltage direct current) test line. The models contain typical standard wires that are generally used to reduce field effects at ground level, neutral conductors placed at lower parts of the DC line, and an earth corona model to intentionally cancel positive or negative ions by generating ions having opposite polarity to ions flowing into the wire. The authors describe experimental results on the effects of these shield wires and a method to predict shielding effects. It is concluded that shielding using the earth corona is quite an effective method; it is even applicable to the reduction of ion density, which has normally been considered difficult