Measurement of AC electric field in transformer oil using Kerr effect

Abstract

In order to clarify breakdown mechanisms in insulation oil / pressboard composite dielectric system, it is effective to measure the electric field distributions. We have investigated the electric field distribution in transformer oil using Kerr electrooptic effect. At first, Kerr constant of the transformer oil was measured using the optical system. The constant was determined to be 2.0×10−15[m/V2]. Next, we measured the electric field in transformer oil in AC electric field in the order of milli-seconds. In order to reduce the error due to the fluctuation of light intensity of the laser, we used the improved optical system. As a result, we have been able to be confirmed that the change of light intensity when AC voltage application was followed to the principle of Kerr effect. In addition, as compared with the result measured by the conventional system, the result could be improved by the new system. Thus, we have been able to confirm that time series electric field measurement on the order of milli-seconds in transformer oil under AC voltage by using optical system based on Kerr effect. In the future, electric field measurement will be performed when partial discharge occurs by applying AC high voltage or pulse high voltage in insulation oil / pressboard composite dielectric system. The electric field distribution before and after the partial discharge will be measured and the breakdown mechanism will be investigated by based on the result.