| Electronic Current Transformer (ECT) has become a new direction of currenttransformers'development for its no saturation under fault current conditions, high levelinsulation and broad range of measurement. However, there is a long way for ECT to bewidely applied, resulting from the disadvantages of its Sensor Head, including theinterference of ambient temperature and external electromagnetism and the difficulty ofmanufacturing technics of itself. This dissertation analysed and designed the Sensor Head ofECTmainlyonovercomingthesedifficulties.This dissertation described the basic principle of ECT, and analysed the ECT based onRaraday mageto-optical effect and Rogowski coil.The composite construction, function andoperation methods of Rogowski coil were described. This dissertation mostly analysed anddesignedtheSensorHeadofRogowskicoil.The current-sensing theories of the Rogowski coils with circularsection and rectangularsection are investigated according to the electromagnetic theories, and the same outputformula of the two kinds of coils was set up. The dissertation analysed self-integrating andadditional integratingoperationmodeofRogowski coil,andthe frequencycharacteristics andthe methods of broadening the bandwidth of Rogowski coil's frequency response under thetwo different operation modes were described. Furthermore, the output voltage, the ways andprinciples of connection in series of Rogowski coils, and the details of amplifying integraphcircuit wereanalysed.The interference of ambient temperature and external electromagnetism with Rogowskicoil were investigated by mathematical models. The relations between relative measurementerror resulting from temperature and heat distensibility coefficient of coil's framework andwindingcoilwerecarriedout. Theinfluenceofelectromagnetisminterferenceontheaccuracyof Rogowski coil, as well as the effect of temperature on integraph, were studied.Somemeasures based on the above investigating results were proposed to insure the precision ofRogowski coil Sensor Head, such as the selection of materials and facture methods,improvment of technics and design of additional compensation. A novel loop-line windingmethod and a magnified circuit with power supply were proposed. At the same time, thisdissertation introduced the principle and design of Print Circuit Board(PCB) Rogowski coil,andinventedanovelPCBRogowskicoil.In the end, this dissertation designed Rogowski coils with four different winding waysaccording to the Rogowski coil's principle and structure as well as interference factors.Experiment result confirmed the correctness and availability of the refered design methods. |
