AC zero crossing compensation for thermal stress linear birefringence in optical voltage transducer

Abstract

The optical voltage transducer (OVT) based on the Pockels effect has a perennial issue of the thermal stress linear birefringence in the electro-optic crystal being overlapped with the electro-optic phase delay, which is difficult to be eliminated and seriously affects the measurement accuracy and reliability. In this paper an AC zero crossing compensation method for thermal stress linear birefringence is proposed. It is based on that when the steady-state AC voltage crosses zero points the electric field is zero, and the electro-optic crystal does not have any electro-optic effect, so the electro-optic phase delay is zero. In this case, the output of the OVT is an additional phase delay caused by the thermal stress linear birefringence, which can be separated and compensated by the linear demodulation OVT and the AC zero crossing detection circuit. The experimental results show that in the temperature range of -40℃ to 70℃, the measurement accuracy of the OVT after thermal stress linear birefringence compensation is improved from 0.5 class to 0.2 class. This method is helpful for the practicality of the OVT.