Optical measurement of change of nonuniform electric field vector distribution in liquid insulator

The reconstruction technique of a electric field distribution which we developed has a merit that the strength and the direction of the electric field at each position on any measured plane can be determined. In order to reconstruct a field vector distribution, it was necessary to measure light intensity twice with changing the optical axis of optical wedges. Moreover, the intensity measurement must be carried out at many points around the electrode system. Therefore we developed a new measurement system with three sets of a optical system with a non-polarizing beam splitter and two image sensors because it took considerable time to measure an electric field distribution. It took a short time, less 100 ms, to map the field distribution using the new measurement system. And the measurement of the electric field distribution at intervals of 40 ms. became possible by the new system. So, we measured of the field distribution every 40 ms in a sphere-to-sphere electrode system, when a negative DC voltage was applied to the electrode system. The obtained results were very interesting