Research On Active Small Current Transformer Based On Zero-Flux

Current transformer is very widely applied both in industrial fields and people’s life. Currenttransformer is an important constituent of power system electric energy measurement, relayprotection, system diagnosis and monitoring. Its measuring accuracy and operation reliabilitydirectly related to the safety and economic operation of the power system. The high precisioncurrent transformer is an important tool for online detection of power system insulation. But forsmall current measurement, the common current transformer’s error is bigger, so it needs tocarry on the error compensation to improve the accuracy of measurement.According to the current transformer’s error formula, this paper analyzes the core structureparameters, secondary side load impedance, the primary side of the input current, the secondarycoil turns and core material which affect small current transformer’s error, and then selects theoptimal small current transformer structure parameters and the core material. On the basis ofin-depth study of the traditional method of error compensation, a zero flux principle-based activecompensation method is proposed, and the derivation of its working principle is done. Thecompensation circuit design is divided into two parts, the hardware design and software design.The hardware design includes the voltage signal conditioning circuit, compensation currentgenerating circuit and single chip microcomputer system circuit, etc. The software design mainlyrealizes the software design of PIC microcontroller’s data acquisition and processing system.Software programming language is C language, and software development environment is in theMPLAB. Finally, the experiment uses the INV306U-5162type acquisition card and DASPsoftware to verify the zero-flux current transformer’s compensation effect. The experimentalresults show that the designed current transformer compensation mode has a good compensationeffect, and it can obviously improve the measurement level.