Dynamic Performance of High-Speed Railway Overhead Contact Line Interacting With Pantograph Considering Local Dropper Defect

The local dropper defect is the most common fault in the early service stage of the overhead contact line (OCL) system. The plastic deformation and loose of a dropper may cause the variation of the contact line height, which has a direct effect on the contact performance of the pantograph-OCL system. This paper proposes a methodology to model the OCL with local dropper defect using a nonlinear finite element approach. Employing a developed TCUD (Target Configuration under Dead Load) method, which takes the vertical defective dropper position in the contact line as additional constraints, the local dropper defect is exactly added in the initial configuration of the OCL model. Several simulations of pantograph-OCL interaction are run with different positions of the defective dropper. The effect of local dropper defect on the pantograph-OCL contact forces is analysed. The results show that the increase of the defect degree causes the increment of the contact force peak around the defective dropper point. The defect on the first or last dropper within a span is the most detrimental to the current collection quality, as it directly causes the increase of maximum contact force, which challenges the safe operation of the pantograph-OCL system, and should be strictly restricted. The PSD (Power Spectral Density) analysis of contact force indicates that the dropper defect distorts the frequency characteristics of the contact force. The energy of contact forces decreases at the dropper-interval related frequencies due to the presence of dropper defect. Similarly, a significant `break' of the dropper-interval frequency component can be observed in the time-frequency representation of the contact force. This phenomenon has the potential to be used to identify and locate the defective dropper from the measured contact force.

I. Introduction

In majority of electrified railways, the Overhead Contact Line (OCL) system is responsible for powering the electric train via a pantograph installed on the car body's roof. Often it is the only source of power for electric trains [1]. As shown in Fig. 1, the OCL normally comprises of two tensioned cables called messenger and contact lines, which are connected by several droppers. The contact line carries the electric current to be collected by the locomotive through the sliding contact with the strip of the pantograph. The messenger line and droppers support the contact line, keeping it at the correct height which may include the reserved pre-sag. Obviously, the quality of the current collection of the electric train is directly determined by the pantograph-OCL interface. Normally, the pantograph-OCL system is the most vulnerable part in the electrified railway, as it suffers multiple impacts from the vehicle-track vibration [2], the temperature variation [3], the irregularities on the contact line [4], the unsteady wind load [5] and some other complicated disturbance [6]. The long-term service under complex work conditions leads to the degradation of the pantograph-OCL performance, which is manifested in contact line wear [7], component failure [8], and geometry distortion [9], resulting in the deterioration of the quality of current collection and the increase in the occurrence of incidents. Pantograph-OCL incidents are the major sources of traffic disruption and train delay. As is well known, the serious accidents that cause fatal consequences are generally developed from small early faults. If the early faults can be effectively coped with, the pantograph-OCL performance can be maintained in a health condition, significantly reducing the occurrence of incidents [10], and the maintenance cost. Fig. 1.

Schematic of a pantograph-catenary system.