# Research on Ultra-Fast Transient Overvoltage Characteristics of Electric Locomotive
###### Abstract  
Operating overvoltage occurs when the pantograph or main breaker of an electric locomotive is operated, which is prone to causing insulation failure of high-voltage equipment. The HXp1 electric locomotive is taken as the research object in this paper to explore the characteristics and influencing factors of operating overvoltage. Under pantograph lifting, main breaker closing, main breaker opening, and pantograph dropping, operating overvoltage waveform in the high-voltage system is recorded by a high-speed oscilloscope and resistance-capacitance voltage divider to analyze the overvoltage characteristics and distribution law. Tested data show that the amplitude of operating overvoltage is in the range of 80 to 330 kV with ultra-high steepness, which is similar to the Very Fast Transient Overvoltage (VFTO) in power systems. The maximum overvoltage during the entire test occurred during the main breaker closing and its amplitude is 328.60 kV with a steepness of \(4.21\times 10^{4}\) kV/\(\mu\)s. The max overvoltage of the other operations (pantograph lifting, main breaker opening, and pantograph dropping) are 280.60 kV, 194.73 kV, and 305.56 kV with ultra-high steepness. High-amplitude overvoltage is predominantly located at the pantograph, while the low-amplitude sort is mainly observed around other high-voltage equipment. The result indicates that operating overvoltage belongs to ultra-fast transient overvoltage and its amplitude and steepness are higher than existing research. HXp1 electric locomotive; ultra-fast transient overvoltage; high-frequency signal test; electromagnetic transient process +
Footnote †: journal: Applied sciences  
In order to analyze the formation mechanism of the fault of the high-voltage equipment on the roof of the locomotive, and to study whether these accidents are caused by the ultrafast and high-amplitude transient operating overvoltage, domestic and foreign scholars have tested the operating overvoltage by various methods. [PERSON] employed a resistance-capacitance voltage divider and data recorder to test the catenary overvoltage of CRH2 EMU during pantograph lifting and dropping, and main breaker opening and closing. The results showed that the amplitude of the operating overvoltage of the catenary was in the range of 40 kV to 70 kV [5]. [PERSON] used voltage divider tape recording equipment and memory oscilloscope to test the overvoltage of pantograph jumping and main breaker closing and opening. The results show that the pantograph jump overvoltage was in the range of 1.24-3.97 p.u., with an oscillation frequency of 1.12 kHz. The overvoltage was not measured during the closing process, the maximum overvoltage generated during the opening process was 7.40 p.u. and its pulse width was 2.32 us [6]. [PERSON] used a PCI-5112 data-acquisition card with a real-time sampling rate of 100 MS/s to obtain the overvoltage test signal from the secondary side of the train transformer, and conducted a test on the pantograph dropping overvoltage. The test results show that the pantograph dropping overvoltage can reach more than 60 kV, and its high-frequency components are concentrated between 200 and 400 kHz [7]. [PERSON] used an HS5 data-acquisition card with a sampling rate of 200 MS/s to obtain the overvoltage signal from the transformer installed next to the pantograph of the CRH5 A EMU. The test results show that the maximum value of pantograph overvoltage can reach 67.10 kV, and the maximum amplitude of operating overvoltage of the main circuit breaker is 138.97 kV [8]. [PERSON] used the capacitive divider and the calculus circuit as the sensing unit, and used the Tektronix DPO 7000 series oscilloscope (Tektronix, Basel, Switzerland) with a sampling rate of 5 GSa/s to test the VFTO in GIS. The measured VFTO overvoltage multiple can reach up to 2.70 p.u. and the UHF component in the waveform can reach up to 100 MHz [9]. In the existing research, the test signal was collected from the secondary terminal of the voltage transformer, which led to signal attenuation and distortion.