Research Of Capacitor Divider Optical Voltage Transducer

Optical transformer is the key basis facility for building of intelligent electric substation. With several decades'development, some practical product of optical current transformer has already launched, but the practical process of optical voltage transformer is relative slow due to its low measuring accuracy and poor resistance to outside electric field disturbance. With the overall development of the intelligent electric network construction, the utility research of optical voltage transformer has become imminent.On the basis of reviewing the existed technology and application, this paper treats the capacitor divider optical voltage transformer as the research object. Against the existing problem during the utility of the optical voltage transformer, the paper thoroughly research on the optimization of high voltage capacitor voltage divider, the optical circuit modeling of optical voltage sensor, the optical voltage sensing technology and the output characteristic of transformer.The outside electric field disturbance for the capacitor divider optical voltage transformer is derived from the effect of inter-phase electric field disturbance to the high voltage capacitor voltage divider. The designed method for high voltage capacitor voltage divider considering the inter-phase electric field disturbance is very important. Combined with the practical operation environment of capacitor divider optical voltage transformer, a high voltage capacitor voltage divider mathematic model is built from the aspect of inner-phase and inter-phase disturbance voltage division. Furthermore, a method is proposed to design high voltage capacitor voltage divider with respect to the simulation software. The validity of the method is tested by experiment.Optical circuit model is an effective tool to analysis the transfer characteristic of the optical voltage sensor, the usually used normal incidence optical circuit model could not accurately describe the transfer characteristic of the optical voltage sensor. This paper derived arbitrary incident polarizing angle optical circuit model and dual optical circuit output model of the optical voltage sensor. The proposed optical circuit model has the general theoretical meaning, and it can accurately describe the effect of disturbing birefringence and the transistor half-wave voltage decided by the temperature variation to the operation quality for the optical voltage sensor.The temperature drift of measurement accuracy for optical voltage sensor is the main reason for the low measurement accuracy. The existing methods improving the measurement accuracy of optical voltage sensor are usually to take measures on some aspect in sensor systems, and this can not eliminate the temperature effect to the measurement accuracy thoroughly. This paper presents a kind of self-healing optical voltage sensing technology by focusing on the optical voltage sensors' system structure. This optical voltage sensor can adapt to the variety of environment temperature. The experiment result shows that the measurement accuracy is improved largely by adopting the technology.The output characteristic for three capacitor voltage of capacitor voltage transformer (CVT), Electronic Capacitor Voltage Transformer (ECVT) and capacitor divider optical voltage transformer (OVT) are compared and analyzed, and the result indicated that the steady-state characteristic and the transient-state of capacitor divider OVT are better than the traditional voltage transformer. Compared with the CVT, The capacitor divider OVT has no the problems of ferroresonance and transient response delay, and it also has no the problems of larger transient measurement error caused by the reclosing on a line with trapped charges versus to the ECVT.Combining the high voltage capacitor voltage divider designing method and the self-healing optical voltage sensor technology presented in the paper, A 220 kV , level 0.5 prototype of capacitor divider optical voltage transformer is developed. The relevant test of the prototype has already been completed, and the prototype has been operating in actual power system in since May 5th, 2010. The test result and the operation conditions show that the presented method which can improve the optical voltage transformer's performance is correct and feasible, and the developed capacitor divider optical voltage transformer has the prospects for practical applications.