Hardware Design And Realization Of A Handheld Transient Magnetic Field Recoder

The secondary equipment, moved to nearby primary equipment in smart substation, will encounter more severe electromagnetic interference, which may cause secondary equipment damage and resulting at protective equipment malfunction or inaction. Studying the electromagnetic environment, analyzing the characteristics of the electromagnetic interference will have an important significance for electromagnetic interference suppression and secondary equipment protection. Field measurement is an important method for researching electromagnetic environment. However, current measuring system is not common and has obvious limitations in use. Therefore, this paper develops a handheld device for measuring, recording and analyzing transient magnetic field(TMF) in substation.The TMF recorder consists of two parts. The first part is magnetic field measuring probe, it used the magneto-resistive sensor based on AMR effect, and the second part is the host, it used the system architecture of FPGA+ARM+ARM. The paper has finished the design of magnetic field sampling analog front end, data relay engine, human machine interaction unit and power supply system. Among them, the magnetic field samlping analog front end focuses on the research of AC channel and amplifying circuit design, and the influence between the gain distribution and the output signal-to-noise ratio, while the data relay engine mainly focused on the interface circuit design between FPGA and DDR2, and the design is verified by simulation. At a result, the recorder has realized the function of real-time waveform display, high-capacity data storage, offline analysis, GPS time scale, USB card reader and human-computer interaction and some others. With the characteristics of simple to installation, easy to maintenance, compact size, convenient to carry, the recorder is suitable for outdoor long time work.Lab experiment of power frequency magnetic field and pulse magnetic field tests the recorder’s performance of measuring power frequency magnetic field and capturing transient magnetic field. The results show that the recorder has good capability to measure the steady magnetic field when substation works normally and to capture the transient magnetic field when switching operation or system failure in substation, effectively.Field measurements, carried at dozens of positions in Jinping-Sunan ±800kV converter station, including bus-bar underneath, ac filter field, GIS room, valve hall and etc, show that the strongest magnetic field appears at 35 kV low-voltage reactor nearby, whose peak-peak value reaches 6Gs, while the magnetic field whose spectrum components is the most abundant appears at nearby pole-I high-end converter outlet, FFT analysis shows that the maximum frequency reaches 893.6kHz.