Non-contact Overvoltage Monitoring Sensor Based on Electro-optic Effect

The measurement of overvoltage in high-voltage power networks is of significance to understand the overvoltage and the design of insulation coordination. In order to measure overvoltage in high-voltage networks safely and accurately, we developed an integrated passive sensor unit based on the electro-optic effect of Li Nb O3 crystal, as well as a non-contact overvoltage monitoring sensor with the unit. The sensor utilizes a series capacitive divider comprised of a long-voltage arm capacitance, which consists of the sensor's own capacitance and a fixed capacitor connected in parallel, and the coupling capacitance between high-voltage line and a metal plate. The electro-optic unit uses full fiber connection, and it only needs to detect the low voltage sensed by the divider unit without requiring power supply at the installation site. Multiple tests of the sensor indicate that the sensor has not only an effective linear operating region but also fast and precise high-frequency responses to both lightning and switching impulse with the error of amplitude below 3% and the time error of response below 0.1 μs. Hence the sensor is applicable to the non-contact passive overvoltage measurement in a wide range of voltage levels.