DC-PROBES FOR ELECTRIC-FIELD DISTRIBUTION MEASUREMENTS

It is desired to measure the external electric field distribution of components for high voltage DC transmission. This information is useful in the development of such components. By measuring the field under a variety of ambient conditions, the performance of both the external and the internal insulation of the component can be assessed. The principles of how DC fields can be measured using an isolated probe coupled by fiber optics to a separate receiver are discussed. The construction of some practical systems are described. We have measured the electric fields around a full size wall bushing energized to 600 kV in rain. The results of this and other measurements are presented. They demonstrate the usefulness of isolated DC field measurements.