# Research on Ultra-Fast Transient Overvoltage Characteristics of Electric Locomotive
## 4 Analysis and Discussion
### Influence of Installation Position and Quantity of Arresters on Ultra-Fast Transient Ooveroltage  
Two tests are carried out on the HX\({}_{\text{D}}\)1C electric locomotive to study the effect of arrester installation position and its quantity on ultra-fast transient overvoltage. For the HX\({}_{\text{D}}\)1 electric locomotive, there is only one on-roof arrester that is located near the high-voltage insulation sleeving, while the HX\({}_{\text{D}}\)1C electric locomotive has two arresters on its roof. One is installed near the high-voltage insulation sleeving and the other is located at the pantograph (as shown in Figure 16).  
It can be seen from Table 6 that for different types of operating overvoltage, increasing the number of arresters can reduce the value of overvoltage to varying degrees. Among them, the most obvious effect of the arrester is the closing overvoltage, which decreases by more than 200 kV. The nonlinear characteristics of the arrester give full play to its function, which can quickly turn on and release a lot of energy. The decrease values of the two closing overvoltages in the table are 225.40 kV and 263.49 kV, respectively. For the rising bow overvoltage, because the value of the voltage is not very high, it is close to the action threshold of the arrester, so the nonlinear response of the arrester is weak, and the resistance drop is small, so the limiting effect of the overvoltage is not obvious. The drop values of the two lifting overvoltages in the table are 49.35 kV and 28.34 kV, respectively.  
The operating overvoltage test process and scheme of HX\({}_{\text{D}}\)1C are consistent with HX\({}_{\text{D}}\)1. After placing the voltage divider, the overvoltage waveform is recorded by a high-speed digital-storage oscilloscope similarly. On the HX\({}_{\text{D}}\)1C electric locomotive, the operation of pantograph lifting, main breaker closing, main breaker opening, and pantograph dropping are tested sequentially two times. The tested data are selected for comparison in Table 6. The peak operating overvoltage of HX\({}_{\text{D}}\)1C is 126.81 kV, which is significantly lower than the peak value of 328.60 kV of HX\({}_{\text{D}}\)1. The results show that a reasonable arrangement of the arrester can effectively reduce the amplitude of the ultra-fast transient overvoltage and provide better protection for the pantograph and other high-voltage equipment on the roof.  
\begin{table}
\begin{tabular}{c c c c} \hline \hline \multirow{2}{*}{**Operation**} & \multicolumn{3}{c}{**Operating Overvoltage**} \\ \cline{2-4}  & **HX\({}_{\text{D}}\)1 (kV)** & **HX\({}_{\text{D}}\)1C (kV)** & **\(\Delta\)u** \\ \hline Pantograph lifting & 176.16 & 126.81 & \(-\)49.35 \\ Main breaker closing & 328.60 & 103.20 & \(-\)225.40 \\ Main breaker opening & 132.72 & 86.04 & \(-\)46.68 \\ Pantograph dropping & 253.70 & 113.91 & \(-\)139.79 \\ Pantograph lifting & 146.63 & 118.29 & \(-\)28.34 \\ Main breaker closing & 315.09 & 51.60 & \(-\)263.49 \\ Main breaker opening & 194.73 & 68.76 & \(-\)125.97 \\ Pantograph dropping & 236.33 & 116.10 & \(-\)120.23 \\ \hline \hline \end{tabular}
\end{table}
Table 6: Comparison of operating overvoltage data of HX\({}_{\text{D}}\)1 and HX\({}_{\text{D}}\)1C.  
Figure 16: Arrangement of arrester of HX\({}_{\text{D}}\)1 and HX\({}_{\text{D}}\)1C.