Abstract
Voltage sensors based on the Pockels electro-optic effect in LiNbO3 crystals have been applied to practical engineering measurements because of their passive nature, wide operating bands, and low transmission loss. However, the temperature of the measurement environment can greatly affect the dynamic responses of these sensors because the natural birefringence of a single LiNbO3 crystal voltage sensor (SVS) is related to its temperature. To improve the stability of this sensor over a wide temperature range, a double crystal compensation method is introduced in this paper to compensate for the natural birefringence of the SVS. A double LiNbO3 crystal voltage sensor (DVS) was fabricated, and its working point drift characteristics and amplitude-frequency response were investigated over the temperature range from 0°C to 50°C. The effects of two intrinsic parameters of the LiNbO3 crystal were also investigated. Comparison between an existing SVS and the proposed DVS showed that the DVS resisted environmental temperature fluctuations more strongly.
Highlights
Voltage sensors based on electro-optical crystals such as Bi4Ge3O12, bismuth silicate and LiNbO3 have been applied in high voltage systems[3,4,5,6,7,8] because of their wide operating bands, rapid response characteristics, low electromagnetic interference characteristics, and low optical transmission loss
The noncontact overvoltage sensor that was previously developed by Chongqing University, which is based on a stray coupling capacitor and the Pockels effect in a single LiNbO3 crystal under transverse modulation, achieves low voltage measurement of the overvoltage signal and provides electrical isolation between the optical fiber voltage sensor and the primary equipment of the power system
As shown by the results, temperature fluctuations will lead to larger deviations in the single LiNbO3 crystal voltage sensor (SVS) working point phase from the linear region near π/2, and the degree of deviation is basically consistent with the fluctuations in the average output and other performance measures of the SVS
Summary
Transient voltage monitoring systems are of major significance for investigation of the overvoltage characteristics of power systems.[1,2] Voltage sensors based on electro-optical crystals such as Bi4Ge3O12, bismuth silicate and LiNbO3 have been applied in high voltage systems[3,4,5,6,7,8] because of their wide operating bands, rapid response characteristics, low electromagnetic interference characteristics, and low optical transmission loss Some of these sensors have high half-wave voltages and low electro-optic coefficients, and are less sensitive to low voltage signals. The data obtained provide an important reference for the field application of these sensors
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