Shielding Effect of Screen Wires to Reduce Shocks to the Public underneath Cahora-Bassa HVDC Transmission Line

Abstract

Transient electric shocks to the public in the vicinity of HVDC lines due to ion currents and high static electric fields is critical design considerations for HVDC transmission lines. These field effects may influence the line configuration and height of new lines. Existing lines which cannot be easily modified, may require retroactive mitigation, particularly where communities have since been established near to the line. Monopolar lines such as Cahora-Bassa may produce more significant adverse effects than comparable bipolar lines due to the lack of mutual field cancellation between the poles and the absence of charge recombination. Shocks have been reported by residents when crossing underneath the negative polarity line of the Cahora-Bassa scheme. The adverse effects of high ion currents and fields can be reduced by the introduction of screening conductors underneath the line. The optimal selection of conductors and their position, as well as the practical implementation of such schemes, is investigated.