The Anti-interference Capability Study On Magneto-Optical Crystal Based Current Transformer

With the rapid development of electric power industry,the important sensor in power system,current transformer is also moving in the direction of large capacity,high voltage,low cost and intelligent.Based on the advanced technology principle,the optical current transformer overcomes many shortcomings of the traditional current transformer,which has become the development trend of the next generation current transformer,and has become an important factor to ensure the stable operation of the power grid.Firstly,the thesis introduces the background of the development of optical current transformer and describes the merits and demerits of the all fiber optic current transformer,the magneto-optic glass current transformer and the magneto-optic crystal current transformer(MOCT).Secondly,the principle of magneto optic crystal current transformer is described.The characteristics of magneto-optical crystal materials have been studied,and the structure of system is desired.Thirdly,it mainly focuses on the analysis of the influence of some facts,such as the external magnetic field and the change of the distance,to the test accuracy.Meanwhile,according to demand of the anti-interference from the external magnetic field,a solution is presented based on the technology of the Coarse Wavelength Division Multiplex(CWDM)which utilizes four sensors to build a measurement system.By using the same optical sensor and laser source,while reducing the cost and improving the signal noise ratio of the system.And then,it introduces an amazing structure called uniformity magnetic ring by the simulation of the Finite Element Method(FEA),which can eliminate the effects of the change of the external magnetic field and the distance variation.Meanwhile,the auto balance circuit can make the signal avoid the influence of the optical path loss and the drift from laser source effectively it can eliminate the common mode noise as well.Finally,it mentions an experiment result which shows that the accuracy of magnetic-optical crystal current transformer can meet the 0.2 accuracy level according to the standard by the multi-sensor measurement method,the sensor structure combined with the uniformity magnetic ring and a reasonable algorithm.In this thesis,some of results,e.g.uniformity magnetic ring structure has been applied for related patents.It will be helpful to make this technology into commercial market.