Contactless Optical Overvoltage Sensor Based on Dual-crystal Compensation

Abstract

Nowadays, the voltage and overvoltage in power system are mostly monitored by traditional contact voltage divider system, which has high operating reliability, but the monitoring method also has some disadvantages such as narrow measuring band, weak ability to resist electromagnetic interference, inconvenient installation and maintenance, and so on. Therefore, based on the electro-optic effect and the principle of air coupled stray capacitance, a dual LiNbO 3 crystal-based contactless optical overvoltage sensor was designed. The sensor's response band can cover 10 Hz~5 MHz, and the voltage proportional coefficient fluctuates less than 2%. The input and output characteristics and temperature stability of the sensor were measured in the laboratory. The test results show that the relative error of the output voltage of the sensor in the range of [-10 ̊C, 60 ̊C] is less than ±5%. Furthermore, a three-phase decoupling algorithm is designed to achieve the application of the sensor in the short circuit voltage measurement of the 500 kV line artificial grounding test.