Summary:

Contact loss and wear of contact wire on overlap sections are larger than those on normal area of Shinkansen. It is important to modify overlap structures to one that can reduce contact loss and wear of contact wire.We measured height and wear of contact wire and acceleration produced on vibrating pantographs of a testing train at overlap sections of JYOETU Shinkansen to investigate the relationship between height and wear or acceleration. Furthermore we calculated current collecting characteristic of overlap sections by simulation. According to the results obtained, we can hold the wear rate of contact wire to an appropriate value by maintaining a constant height of the wire.

Key words : overhead contact line, overlap section, contact wire height, wear of contact wire　

1. Introduction

Overlap sections are discontinuous spots on overhead contact line. It is desirable to reduce contact loss and wear of contact wire which are caused by inadequate position of contact wires. We investigated overlap sections of JYOETU Shinkansen by a new type measuring instrument which can measure height and wear in two groups of contact wire at the same time. Referring to the investigated results, we made an analysis of wear vs. height relation of contact wire and acceleration produced on vibrating pantographs of a testing train. Furthermore we calculated current collecting characteristic of overlap sections by simulation. According to the results obtained, we can hold the wear rate of contact wire to an appropriate value by maintaining a constant height of the wire.

2. Development of new type measuring instrument

We developed a new measuring instrument which can measure the overlap structure accurately and rapidly. The measuring instrument has a laser sensor for wear and a displacement sensor for height of contact wire in two groups. It can do so in two groups at the same time. Overlap sections are formed in 2 spans on Shinkansen lines. One division of overlap section can be measured by the maintenance car in one trip at a speed of 4km/h. It processes and outputs a signal on a continuous chart. Details of measuring instrument are shown in Table 1. We investigated overlap sections at 50 places to analyze wear vs. height relation of contact wire on Shinkansen by this instrument.　

3. Analytic results of wear vs. height relation of contact wire.

Depending on the wire height we classified the measured results into 4 kinds (Table 2). Line A shown in the table is contact wire before the pantograph passes the overlap section and Line B is contact wire after that. We judged quality by a progressive degree of wear of contact wire in 4 kinds of overlap structure. uJ and uLtypes are good structures with no severely worn spot at the crossing point. On the other hand, uKand uMtypes are poor structures with severely worn spot at the crossing point. In uK and uMtypes wear progresses farther than in other types because pantographs can not pass a crossing point smoothly. A measured example of uM type is shown in Figure 1. The support points which are shown in the chart are signals showing that a cantilever pipe was detected by a photoelectric sensor. The signals of contact wire height show the condition where upper direction of form wave is high. Line B at a crossing point is lower about 25mm than Line A.
The signals of wear of contact wire show the condition in lower direction of form wave where wear is progressing. Waves looking like a mustache show positions of metal fittings,for example, a dropper. In this case progress of wear is seen in Line B at a crossing point.
A measured example of‡V type is shown in Figure 2. Line B at a crossing point is higher about 15mm than Line A and there is not any severely worn spot at a crossing point.

4. The acceleration which occurs on the pantograph

In order to judge quality of an overlap structure, we measured the acceleration which occurs on the pantograph in a test train passing the overlap section. The speed of a train is almost fixed at 220 〜240km/h. Conditions of acceleration which occurs on the sliding shoe of pantograph are shown in Figure 3. Value in the graph is the largest one averaged for every type. The values for uJ and uLtypes which are regarded as good structure are lower than uK and uMtypes which are regarded as poor. This result agrees with the judgment based on the progress of wear of contact wire.

5. Simulation analysis

5.1 Simulating conditions

We classified overlap structures into 4 groups in terms of pantograph acceleration and height and wear of contact wire measured on JYOETU Shinkansen, and made clear their current-collection characteristic. It is, however, difficult to determine the most suitable structure only from measured results which don't include all conditions of overlap structures installed on Shinkansen. Then to determine the most suitable structure we carried out a simulation analysis which is used to predict current collection characteristic of overhead catenary-pantograph system [1]. Values of facilities installed on JYOETU Shinkansen were adopted as constants in simulation of overhead catenary-pantograph system (Table 3). There are 10 spans which are composed of 4 spans of normal section followed by 2 spans of overlap, and again 4 spans of normal section. Contact-loss and contact force between pantograph and contact wire which are calculated by simulation are compared with contact wire heights of overlap as follows :

(1) Height differences between Line A and Line B : -40 mm 〜 50 mm (‡W,‡T,‡Vtypes)

(2) Pulling up quantity at crossing point : 0 〜 50 mm (‡Utype)

5.2 Simulation results

Figure. 5 shows contact-loss rate (mean values for 3 pantographs). Contact-loss rate has no difference between overlap structures at 220 km/h, but at 240 km/h and 260 km/h the overlap structure in which Line B is 0 〜 30 mm higher than Line A has a smaller contact-loss rate than other overlap structures. When height difference and pulling up quantity are larger than 30 mm, contact-loss rate shows a tendency to become larger.
Maximum values of contact force are shown in Figure. 6. These values are smaller at every speed when height difference is 0 〜 30 mm and pulling up quantity is 0 〜 10 mm, but they show a tendency to become larger when height difference and pulling up quantity are larger than others. It is likely that the greater the contact force, the larger the wear of contact wire because mechanical wear is superior to electrical wear at Shinkansen.
From what is mentioned above we can conclude that the range where no wear of contact wire occurs at overlaps is height difference 0 〜 30 mm, and pulling up quantity 0〜 10 mm. These calculation results agreed with measured ones.

6. Conclusions

We carried out an investigation of overhead catenary at JYOETU Shinkansen in order to determine the most suitable structure of overhead catenary and judge quality of overlap structures from wear of contact wire obtained from the investigation. Conclusions are as follows :

(1) It is possible to reduce contact wire wear at overlap in Shinkansen when overlap structures are designed like the structures proposed in (2).

(2) Desirable overlap structures are such that the height of Line A equals that of Line B, or Line B is higher than Line A at crossing points (height difference allowable between them is 0 〜30 mm). Measured results agree with simulated ones.

Reference

[1] Y. Fujii. K. Manabe. , Computer Simulation for Dynamics of Overhead Catenary-Pantograph System , Comprail '92, 1992.8