Design On The10kV Combined Electronic Transformer

The ceaseless rising of voltage grade and the increasing capacity of electric power in the power system are putting forward higher requirements to the power transformer. The traditional transformer has their own disadvantages which are difficult to solve, such as, magnetic saturation phenomenon, ferromagnetic resonance, volume and weight always being large, no digital output and so on. It is clear that the traditional transformer can not satisfy the new requirements of digital and intelligent development in electric power systems. At present, based on the modern sensor, measurement technology and computer technology, the electronic transformer is gradually becoming the substitutes of traditional transformer with a rapid development. Electronic transformer has no magnetic saturation phenomenon, large dynamic range, wide frequency response, relatively simple insulation, small volume and light weight, and it can provide digital output. In view of the miniaturization and intelligent development trend of switching devices in the power system, a set of10kV combined electronic transformer has been designed based on the comprehensive analysis of the present research and application about the domestic and foreign electronic transformer.In this paper a current sensing portion and a voltage sensing part of the combined electronic transformer have been designed. And the electronic voltage transformer takes a tank type capacitor voltage divider as the sensor, which actually makes a coaxial cylinder capacitor ring as a high voltage capacitor to realize the measurement. In addition, electronic type current transformer uses Rogowski coil as the sensor.The Rogowski coil and capacitor divider structure parameters have been theoretically deduced and calculated. This paper has also analyzed the factors which influence measurement accuracy of the sensor; and made a shielding box to the hollow coil according to the research about the electromagnetic interference.The hardware design of the signal acquisition and processing circuit has been completed in this paper. The entire circuit can achieve signal synchronous acquisition on multiple channels, which adopts TMS320VC5409as the core control and signal processing chip, and uses analog to digital converter AD7656 as the core signal acquisition chip. In addition, the test system has initially been set up.According to IEC60044-7and IEC60044-8standards, the initial performance tests of the combined electronic transformer sensor parts have been completed, including the transformer ratio test, angle difference test and anti interference performance test. Test results show that the measurement accuracy of the electronic current transformer sensor can meet0.2requirements, the measurement accuracy of the electronic voltage transformer sensor meets0.5requirements.