Unified Perturbation Analysis Method Of Optical Effect And Its Application In Voltage Sensing Technique

Power system has entered the era of smart grid, and intelligent substation is the key part of smart grid. As the essential equipment of intelligent substation, optical voltage transformer(OVT) is in urgent need of research on its practicality. Aiming at the practicality of OVT, this dissertation studied the optical voltage sensing technology based on the electro-optic effect.The basic theory of optical voltage transformer is Pockels electro-optic effect. Besides electro-optic effect(known as primary effect), there is disturbing optical effect(known as secondary effect) caused by stress, temperature and other environmental factors in the sensing medium. The temperature drift on measuring accuracy caused by secondary effect is the key problem which hinders the application of OVT. Based on tensor analysis, this paper probed a unified perturbation analysis method of primary and secondary effects, and then deduces the integral Jones matrix of inhomogeneous medium. On this basis, an actual sensing model of OVT was built and methods resolving the problem of temperature drift effect were proposed, which will contribute to the development of OVT with high accuracy and high temperature stability. The main research contents are as follows.First of all, a unified perturbation analysis method of optical effects was proposed and used to analyze electro-optic effect. According to Hermitian symmetry of medium tensor under the impacts of various optical effects, based on the perturbation theory, this dissertation established the quaternary symmetry system of non-redundancy intrinsic equation by applying the micro quantity algorithm. Quaternary symmetry system of intrinsic equation is universal system that can apply to any optical effect analysis. Using this method to analyze the electro-optic effect, a procedure to calculate the refractive index difference of electro-optic medium was designed. By comparing with the current analysis method, the validity of this method was verified.Secondly, according to the inhomogeneous characteristic of medium induction tensor, the integral Jones matrix of inhomogeneous medium was proposed. The unified perturbation analysis method showed the optical property of a certain point on the travel path of medium, while the Jones matrix represented the accumulation effect of optical properties of each point on the travel path on the optical wave, which was greatly affected by the inhomogeneity of medium induction tensor. When the induction tensor is inhomogeneous, the phase shifting matrix of medium is represented in the form of integration, and so will be the Jones matrix. Integral Jones matrix covers different optical effects, making it widely applied.Thirdly, the actual sensing model of OVT was built. Using the unified perturbation analysis method, the impact of secondary effects on optical voltage sensing system was analyzed. On the basis of integral Jones matrix, the optical characteristics of optical medium were solved under the concurrence of primary and secondary effects, and the actual propagation process was analyzed. Based on the actual operation environment of the OVT, an actual sensing model of OVT was built and corresponding analysis was conducted.Finally, a high accuracy self-calibration OVT was developed. According to the refractive index difference calculation procedure of electro-optic medium, the relationship curve between sensing system modulation degree and optical wave direction parameters was drawn. And the modulation method of sensing system was designed according to the curve. Aiming at the problems of the temperature drift on the measuring accuracy, a self-calibrating method of OVT was proposed on the basis of actual sensing model. Besides, the realization process of self-calibrating technique in the optical voltage sensing system was analyzed and comparative tests of optical voltage sensing system before and after the adoption of self-calibrating technique were conducted, thus verifying the effectiveness of this technique as a solution to the secondary effect and temperature drift effect. By applying the self-calibration optical sensing system to OVT design, a 220 k V high accuracy self-calibration OVT prototype was developed and the relative tests were conducted. The test results showed that the self-calibration OVT had higher measuring accuracy and better temperature stability, which achieved the 0.2 level measurement standard and 3P level protection requirement of OVT. At present, this OVT had been network operating in the actual power system.