Research On Failure Mode Of Current-carrying Integral Droppers Of Overhead Catenary

The power of the high-speed EMU comes from the pantograph-catenary system.The catenary is an important component and landmark of electrified rail transit.The dropper is an important part of the catenary.It not only transmits the mechanical vibration between the loadbearing cable and the contact line,but also carries the current between the contact line and the load-bearing cable.Therefore,the dropper is to ensure the safety of the catenary.In the past ten years,a large number of dropper failures have occurred on many lines.In view of the importance of the dropper in the catenary system,it is necessary to systematically study the failure mode of the dropper.This article takes the overhead catenary current-carrying integral droppers as the research object,and comprehensively uses theoretical analysis,parameter calculation,modeling and simulation,fatigue experiment and other means to explore its failure mode and fatigue characteristics.First of all,starting from the actual situation,we summarized many factors that caused the droppers failure,including fatigue theory,electroplastic effect,softening theory after heat treatment,etc.Secondly,calculate the relevant parameters of the droppers under the actual working conditions.Starting from the calculation principle of the coupled parallel wire circuit,the parameters of each part of the traction network are calculated,and the droppers current curve is obtained on this basis;the mechanical load parameters are based on the relevant theory of the catenary,combined with the actual measured values to establish a simulation model,and obtained using ANSYS simulation.Finally,the droppers fatigue test under electrical action is carried out with reference to the requirements of domestic and foreign droppers fatigue tests.The test was conducted in three groups,describing the impact of large current under short-circuit fault conditions,current under normal working conditions and railway standard inspection current on the fatigue life of the droppers.According to the current distribution model of the catenary,the existence of the currentcarrying integral droppers is equivalent to multi-point parallel connection between the contact line and the load-bearing cable,and there are only 4 to 5 droppers carrying current on both sides of the converter point.When the converter point is in the middle of the catenary,the relationship between the droppers current and the distance between the bow-net interface is similar to the normal distribution,and the electrical load of the droppers reaches the maximum when the pantograph is directly below the droppers.From the results of the bow net simulation,it can be seen that the maximum static value of the droppers and the maximum value of the maximum force appear in the droppers at the middle position of each span,that is,the third dropper.Fatigue test results under electrical action show that the dropper fatigue test is carried out while continuously carrying current,and the average life of the droppers is about 20% lower than the average fatigue life of the non-current-carrying droppers.The average fatigue life of the droppers is reduced by about 40%.The experiment also found that the resistance of the droppers increased with the increase of the number of vibrations,and the resistance value fluctuated sharply and increased sharply immediately before fatigue fracture,until it suddenly broke.This discovery also provides new ideas for the maintenance work of the droppers.