On the Measurement of Fields produced by Sea Return Electrodes for HVDC Transmission

The use of HVDC transmission is spreading worldwide, for a number of reasons. When return electrodes are used, their compliance with international technical standards and environmental limitations has to be assessed after commissioning, before regular operations can start. While the measurements of the fields produced by ground return electrodes is basically derived by the techniques developed over the years for industrial grounding plants, when sea electrodes are used things are more complex, the instruments and measurement techniques are less common. In this paper, we try to summarize the issues and to describe the relevant techniques than can be used.