Measurement of AC electric power based on dual transverse Pockels effect

A novel optical method for the measurement of ac electric power has been developed. It is mainly based on the electrooptic crystal multiplier, which is designed according to the dual transverse Pockels effect. By using this electro-optic device, the polarized light propagating along the threefold axis of the crystal can be modulated by the product signal of two orthogonal electric fields perpendicular to the light beam. Therefore, by separately converting the load current and load voltage into two transverse electric fields and simultaneously exerting the fields to the crystal, the instantaneous electric power signal can be obtained from the modulated emerging light. The optical sensing unit is merely composed of a polarizer, an electro-optic crystal, and a polarization beam splitter. The active power and apparent power can be measured simultaneously. The experimental results for the measurement of ac electric power employing a lithium niobate (LiNbO₃ or LN) crystal show good agreement with the theoretical analysis. The uncertainty and sensitivity of the measurement are also discussed. The research work presented in this paper will provide the theoretical and experimental foundation for the practical optical electric power transducer based on the dual transverse Pockels effect