| High-speed train has been developing at an alarming rate in China for its characteristics of speediness, large carrying capacity, energy saving, high safety performance, and so on. However, with the increasing speed of high-speed train, the traction power and the return current are both rising gradually, and the time passing phase, operating pantograph become more and more frequent, leading to overvoltage occurs frequently on train. Thus will causes of insulation breakdown of HV (high-voltage) equipment and emergency parking of train. In addition, the shielding layer of the HV cable is connected to carriage roof, whose layout is complicated and so long. As soon as pantograph operating, the surge voltage will generate between the core and shielding layer of HV cable, then couples to the roof of carriage and spreads to the other carriages. On the one hand, the surge voltage is likely to cause electromagnetic interference and logical confusion of vehicle control and communication system, and even damage the vehicle-mounted components. On the other hand, a large number of traction current through the bearings will result in its breakdown by surge voltage, leading to electric corrosion of bogie bearings. Thus, it is a great threaten to high-speed train and safety of passengers.Based on the traction substation, catenary, circuit structure of train, and steel rail, considering the distribution of HV equipment and grounding system of high-speed train, the transient overvoltage in the process of pantograph operation was studied. The generation mechanism, amplitude and frequency of overvoltage on high voltage equipment and carriage were analyzed theoretically. The influence of backflow on HV cables was researched. The stray capacitance of HV cable will be charged and form vibration with inductance and resistance of the traction power supply system in the process of pantograph rising, then formed overvoltage. The stray capacitance of high voltage cable will vibration with inductance of the voltage transformer when pantograph falling, the amplitude of overvoltage is mainly related to the oscillation frequency of the circuit and the angle of voltage phase.By using OrCAD/PSPICE circuit simulation software, the model of traction substation, catenary, steel rail and circuit of high speed train systems is established under distribution parameters. Through the simulation model, the amplitude, oscillation period and duration time of the surge voltage on HV equipment and carriages were researched, and the influence of backflow on HV cables was analyzed. It can be concluded that, the amplitude of overvoltage on pantograph which is caused by pantograph lowering is about 2.4 times of pantograph rising. When rising pantograph, high-frequency oscillation will appears at the end of the HV cable and it is approximately twice the original voltage. In addition, the maximum surge voltage on each carriage reached many thousands of volts and the voltage only a few hundreds of volts when lowering pantograph. Finally, the field experiment was carried out to measure the transient overvoltage from carriage to rail and verified the simulation results.The regularities between the overvoltage and the voltage phase of catenary, excitation induction of voltage transformer and the parameter of grounding resistor was explored based on simulation model. In addition, a suggestion to suppress the surge voltage on carriage was proposed. It is suggested that the surge voltage on carriages can be reduced by paralleling 0.5μF capacitor to grounding resistor in some extent. |
PDF Full Text Request