An Optical Electric Field Sensor for AC and DC Electric Field Measuring

The technology of electric field measurement is an important method to obtain the transient process of power system, such as the overvoltage caused by switching operation. The optical electric field sensor based on Pockels effect is non-contact measurement, which has better performance and more flexible application than the traditional methods. The electro-optic crystal is the key part of the sensor, and different kinds of crystal has different charge relaxation time constant, which causes problem when measures DC electric field. In this paper, an optical electric field sensor in type of common path interferometer with LiNbO3 crystal is proposed. The response characteristics of the sensor is verified by AC electric field under different waveforms and frequencies, and DC electric field. Experimental results show that the proposed sensor can be used to measure both AC and DC electric field. The waveform of transient overvoltage recorded in UHV AC and DC substation are employed to test the performance of the sensor to real application scenario, and the results indicate good performance of the sensor.