Introduction to 200kV RC voltage transformer

Author： GOZ Electric Time：2024-11-25 09:46:30 Read：13

In order to study the impedance matching inside the 200kV RC voltage transformer, the working principle of the RC voltage transformer was analyzed, and the MATLAb simulation model of the transformer was established based on the actual parameters. The internal impedance matching effect of the transformer is not good, and the oscillation cannot be completely eliminated. More effective impedance matching measures need to be added. The low-pass filter is used as an effective impedance matching measure, and the impedance matching effects of different filters are compared and analyzed. The results show that compared with the RC passive filter, the second-order Butterworth filter has better filtering characteristics and more stable performance, and is a more reliable and effective impedance matching measure.

Keywords: voltage transformer; RC voltage divider; impedance matching; cable transmission; maylab simulation model; Butterworth low-pass filter; signal distortion; DC voltage transformer

The 200kV DC voltage transformer is an important device for measuring the voltage of the high-voltage DC transmission system, which provides accurate and reliable voltage measurement information for the control and protection of the system. Since the RC voltage divider has the advantages of good amplitude-frequency characteristics, high linearity and good response characteristics, and the frequency band range of the RC voltage divider is wide, it basically covers the entire measurement voltage range from DC, power frequency to impulse voltage. Therefore, the RC voltage divider DC voltage transformer based on the RC voltage divider has been widely used. Usually, the characteristic impedance of the coaxial cable is much smaller than the input resistance of the merging unit. When the measurement signal wave is transmitted to the end of the cable, it is inevitable that reflection will occur and the reflected wave is large. If there is no impedance matching measure at the head end of the transmission cable, the signal wave will be reflected at the head end of the cable, causing the change of the measurement voltage divider ratio and the oscillation of the measurement waveform, resulting in the distortion of the transmission signal. Therefore, it is of practical significance to study the impedance matching inside the RC voltage divider DC voltage transformer and propose effective impedance matching measures.

Domestic and foreign scholars have conducted certain research on the impedance matching problem inside the voltage transformer. The impedance matching circuit of the resistor voltage transformer is designed, and the selection of each part of the impedance matching circuit is studied; the impedance matching of the resistor voltage divider measurement system is introduced, and the influence of the impedance mismatch of the measurement system on the voltage divider ratio and the oscillation of the measurement waveform is studied. The impedance matching problem of the resistor voltage divider in nanosecond high-voltage pulse measurement is studied from the two aspects of high-voltage lead and coaxial cable. In summary, most of the current research on the impedance matching of the transformer focuses on the impedance matching problem of the resistor voltage divider in the pulse measurement test. However, the research on the impedance matching of the resistor-capacitor voltage transformer is still not sufficient.

This paper studies the working principle of the resistor-capacitor voltage transformer and establishes a MATLAB simulation model of the resistor-capacitor voltage transformer based on actual parameters. The impedance matching inside the transformer is explored, and the impedance matching effect of the transformer merging unit is tested experimentally. Finally, effective impedance matching measures for the resistor-capacitor voltage transformer are proposed, and its matching effect is verified by simulation.

Working principle of DC voltage transformer

The RC voltage transformer is usually composed of a RC voltage divider, a double-shielded cable and a merging unit module, in which the RC voltage divider includes a high-voltage arm and a low-voltage arm, which are composed of multi-stage resistors and capacitors in series and parallel. The merging unit module includes: a secondary voltage divider circuit, a conversion module and a data merging unit. The low-voltage measurement signal is converted into a DC voltage signal of a lower voltage level through the secondary voltage divider circuit, and after signal processing such as digital-to-analog conversion, data merging, and optical fiber transmission, an analog signal or digital signal that meets national standards is output.