光学电压互感器的电场分布对测量的影响

Influence of the Electric Field Distribution on the Optical Voltage Transformer

基于Pockels效应的光学电压互感器(OTV)中电极间的电场分布对电压的测量结果影响很大。用有限元法计算了纵向和横向调制情况下用BGO晶体作为传感介质的OTV的电场分布,讨论了电场的不均匀性对测量结果的影响。计算表明:在不均匀电场中,OTV的标度因数与均匀电场条件下的估算值有出入;OTV的标度因数将随入射光线的位置和角度变化而变化,会影响测量的稳定性;纵向调制比横向调制优越,因为纵向调制利用的是对称中轴附近的电场,均匀性较好,而横向调制利用的电场将受到边缘效应的干扰。

In the optical voltage transformer based on Pockels effect, the electric field distribution between two electrodes is very important to the measurement results. An optical voltage sensor based on the BGO crystal is investigated with the finite element method （FEM）. The electric field distribution between the two electrodes in the case of longitudinal modulation and transversal modulation is simulated respectively. The influence of the electric field nonuniformity on the measurement is discussed. The simulated results show that in a non-uniform electric field, the calculated scale factor is different from the approximation obtained from the uniform electric field assumption, and the difference is determined by the degree of non-uniformity. In the case of non-uniform electric field, the scale factor is also changed by the position and angle of the input light, thus the stability is influenced. Meanwhile, it is also shown that with the same set-up, the longitudinal modulation is preferred over the transversal modulation, since the electric field around the symmetric axis in the longitudinal modulation is more uniform. The electric field used in the transversal modulation is disturbed by the fringe effect, which will degenerate the stability.