## 6 On-Site Experimental Measurement and Results Analysis of Converter Transformer  
### Introduction to Converter Transformer Parameters  
The DC resistance tested converter transformer from the Dongfang converter station in Shenzhen is selected as the experimental object. The actual transformer of the Dongfang converter station is shown in Figure 15.  
The converter transformer tested in this article is produced by TBEA (Changji, Xinjiang, China). The transformer model is a ZZDEPZ-237400/500-600 single-phase double winding converter transformer, and the transformer name \begin{table}
\begin{tabular}{c c c c} \hline \hline
**Preset Residual** & **Starting** & **Endpoint Remanence** & **Error (\%)** \\
**Magnetization Value (T)** & **Remanence (T)** & **Value (T)** & **Error (\%)** \\ \hline
0.8 & 0.78477 & \(-\)0.00148 & 1.719 \\
0.7 & 0.72231 & 0.01384 & \(-\)1.21 \\
0.6 & 0.59941 & 0.02367 & 4.043 \\
0.5 & 0.50399 & 0.02466 & 4.134 \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Measurement data based on toroidal transformers. Figure 14: Smoothed dynamic hysteresis loop. Figure 15: Physical picture of a converter transformer at the Dongfang converter station. Introduction and Operation Process of Integrated Device for Residual Magnetism Measurement and Demagnetization  
Figure 16 is a schematic diagram of the residual magnetization measurement and demagnetization device for the converter transformer, where 1 is the voltage output terminal, 2 is the emergency stop button, 3 is the mode switch button (which can be switched to impedance measurement mode or demagnetization mode), 4 is the demagnetization direction switch (which can choose forward demagnetization or reverse demagnetization), 5 is the start button (which can start the demagnetization process or impedance measurement process), 6 and 7 are the RJ45 and USB output ports, 8 is the device's main switch, 9 is the power input port, and 0 is the device ground interface. The main technical indicators of the device are shown in Table 6:  
This residual magnetism elimination device mainly consists of a computer control unit, device power supply, residual magnetism data acquisition unit, energy storage capacitor, current direction controller, demagnetization data acquisition unit, and output control unit. The computer control unit serves as the main control CPU and is connected to the device power supply, intelligent high-voltage voltage regulation unit, residual magnetism data acquisition unit, energy storage capacitor, current direction controller, demagnetization data acquisition unit, and output control unit to achieve the control and data exchange of each unit. The power supply of the device provides power for the computer control unit and intelligent high-voltage regulation unit, and is also the power source for the energy storage capacitor. The voltage regulating unit is connected to the residual magnetism  
Figure 16: Integrated device user interface diagram. \begin{table}
\begin{tabular}{c c} \hline
**Parameter** & **Value** \\ \hline Rated capacity & 237.4 MVA \\ Transformer type & Converter transformer \\ Rated frequency & 50 Hz \\ Short-circuit time & 2 s \\ Tap position & +20, N, \(-6\) \\ Voltage (V) & 656,250, 616,120, 485,625 \\ Current (A) & 627.6, 673.2, 846.7 \\ Secondary voltage (V) & 616,120 \\ Secondary current (A) & 2250.8, 2250.8, 2250.8 \\ Rated current & 2 \(\times\) 1300 A \\ Rated voltage & Um 72.5 kV \\ Load loss & 485.4 kW \\ No-load loss & 142.8 kW \\ No-load current & 0.082\% \\ \hline \end{tabular}
\end{table} 
Table 5: Measurement data based on large converter transformers. data acquisition unit and the energy storage capacitor, and the residual magnetism data acquisition unit transmits the data to the output control unit. The energy storage capacitor is connected to the current direction controller, which receives instructions from the computer control unit and adjusts the output according to the state of the energy storage capacitor.