A non-contact electro-optic sensor for lightning overvoltage measurement

Measurement of Lightning overvoltage in high voltage power network is of great significance to the research on the characteristics of overvoltage and the design of insulation coordination. In this paper, an integrated passive sensor for overvoltage measurement is designed. A high voltage sensing unit is constituted by a capacitor with fixed value in series connected to the stray coupling capacitor between the high voltage transmission line and metal plate as a series capacitive divider. The electro-optic unit is designed based on the electro-optic effect of LiNbO₃(LN) crystal. The voltage signal sensed by the front unit can be converted to an optical signal by electro-optic unit with no power supply at the installation site. The electro-optic unit is connected with control room by optical fibers. Tests on the new developed overvoltage sensor indicate that the sensor has not only a good linear operating region, but also a high precision and high frequency response speed under lightning and switching impulse. It can be applied to the non-contact passive measurement of lightning overvoltage in different voltage levels.