Study On The Optical Voltage Transformer

The disadvantages of traditional voltage transformer, such as difficult-insulation, narrow-bandwidth and danger of burning and blast, become obvious step by step with the increasing voltage class and power capacity. It directly affected safety running of power systems. The optical voltage transformer (OVT) overcomes many disadvantages of traditional voltage transformer. It has a great future.This paper discussed the basic principle of optical voltage transformer that measures high-voltage in electric power system. This OVT is based on BGO's Pockels effect. The refractive index of BGO changes when an electric field is applied to them. Injecting a linearly polarized beam into the BGO causes the beam to be divided into two linearly polarized beams. The voltage applied can be perceived by measuring the phase difference of the two beams with the help of the two polarized beam interferometry.The OVT's modulators often apply longitudinal and transverse modulators. This paper analyzed their advantage and disadvantage, and improved longitudinal modulators. This analysis shows that the improved longitudinal modulators have high immunity to electric field interference and simple signal process. Furthermore dual-beam-channel compensation method can be applied to longitudinal modulators, which can eliminate the errors arisen from interferefering birefringence to some extent. The structure substituted rectangular prism for common quarter wave, and improved the stability of the optical voltage transformer.The stability of optical voltage transformer is the key to holdback the OVT to be applied to practice. The paper discussed detailedly the stability, the origin of error from the aspect of construction, material et al, and the method of eliminating error. It provided the theoretic direction for OVT's practical application.The fiber transmission system acts as transferring information and insulation. It is a necessary part of OVT and an important factor of influencing the precision. The paper analyzed the fiber transmission character and the performance of emission and receiving module, and had a trial. The trial showed that this system had a good linearity, and it can be used for OVT.The paper also analyzed the request of the OVT for the A/D converter. We designeda sampling board with a 12-bit A/D converter. The trial indicated that the veracity and reliability of the board accord with the request.