A DC Electric Field Measurment System in Transformer Oil Based on Kerr Electro-optic Effect

• 1、Dept. of Electrical Engineering

Abstract：Space charge accumulation can seriously effect the insulation system under dc voltage. So the real electric field distribution or space charge distribution plays a significant role in the development of insulation system of power equipments. The electric field measurement method based on Kerr effect can not affect the electric field distribution under test and can obtain the electric field distribution on-line. For the small Kell constant of oil, ac modulation method is conducted during the measurement of dc electric field in oil in this paper. During the dc electric field measurement, a low ac voltage (about several hundreds voltage) are superimposed on the tested dc voltage. The dc electric field can be calculated using the dc and ac signal components through the optic intensity of the photodiode. During the measurement of electric field distribution based on Kerr effect, the output of the photodiode is connected to a phase lock amplifier, by which the dc and ac signal components needed to calculate the electric field are obtained. This method can get the final results of the dc and ac signal components. The validity of the measurement system is confirmed by the results.

Keywords： insulation system dc electric field electro-optic effect electric field measurement measurement system