Research On Rogowski Current Transformers For Measuring Steady And Transient Currents

Current transformer (CT) is important equipment in power system, which plays a very important role of measurement, monitoring and protection in power system. As the voltage level of power system continues to improve, the conventional electromagnetic current transformer encounters with more and more problems in the process of using. Such as the increasingly large volume, the increasingly high cost of insulation, and the danger of explosion and insulation breakdown. What's more, the inherent problems about magnetic saturation lead to the incorrect measurement of the fault current, which has been difficult to meet the demand of the intelligent and digital of the future power system. While the Electronic Current Transformers (ECT) show its broad application prospect in power system for its wide measuring range, broad dynamic response, simple insulation structure and easy access to digitizing system. With the power system developing toward the trend of digital, intelligent and the publication of related standards: IEC60044-8, IEC61850, which guides for the studies and design of the ECT, the development of ECT is promoted.In this paper we firstly describe the principle of ECT and its development in detail, and then, we analyze the structure of the current transformer based on Rogowski coil. We have also done a detailed analysis and design in all sectors from sensing to sampling in the high-voltage side of Rogowski current transformer, and we have established a model simulation circuit for Rogowski coil measurement system aimed at the frequency characteristics simulation. And we have designed an automatic range switch circuit toward high sampling frequency in accordance with the characteristics of current network. The article also analyzes the sampling and control circuit of the ECT especially so as to meet IEC61850 standard, and designed the synchronized sampling control system based on PLL, which makes the ECT meet the demands of information analysis and processing.The paper analyzed the impact of coil parameters on frequency characteristics of its measuring system, and pointed out preventing the phase error caused by the distributed capacitance of the coil in low-frequency signal measuring. The range switch circuit by pure hardware circuit has higher real-time property. Using AD7606 sample all sensors with high speed and achieve sample collocation for both ECT and EVT to meet the demands of precision and flexibility in the measuring. This paper provided the experience for designing and analysis of the Rogowski current measuring system, with a certain reference.