Research On Digital Signal Processing Scheme For Optical Current Transformer

With the successive increment of the power transmission capacity and the rising of the voltage of the electrical network, conventional current transformers have exposed several intrinsic shortcomings that cannot be overcome. The advanced electronic current transformers (ECT) which adopt electronic, optical and optical communication technologies have many advantages such as no iron core, light weight, no magnetic saturation, larger range of dynamic response, immunity to electromagnetic interference, etc. In recent years, as the developing of microelectronic technology, the applications of digital signal processing techniques are deepened, and the conditions for the practical applications of ECTs become more and more mature. ECTs will replace tranditional current transformers step by step.The basic theory of ECT is stated, the working principles of passive (based on magnero-optic effect) and active (based on Rogowski coils) ECTs are introduced, the advantages and disadvantages of tranditional signal processing circuits are analyzed, after the intensive studying of the technical standard of IEC60044-8:2002, a digital signal processing scheme used for a passive ECT is proposed, the details of hardwire circuit design and softwire algorithm realization are reported. Compared with the tranditional one, this scheme has advantages such as enhanced signal processing abilities, higher precision, simultaneous realization of temperature compensation and non-linear compensation etc.The work reported in this paper might be a reference for the researches and developers working in ECTs area.