Development of overhead line maintenance applying
high frequency data collecting system
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Hiroshi YAMAMOTO , Toshihide KISHI , Atsuhiro TAKAHASHI
1.
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East Japan Railway Company, Saitama-City. JAPAN
Contact: e-mail :yamamoto-hi@jreast.co.jp
Abstract
JR East is developing an overhead line condition monitoring system to be equipped on operating train
so as to obtain high frequent data about overhead line. We are testing and evaluating the system. If the
result is good, we would plan to extend the maintenance system on operating train to mainly convention
lines. And for the purpose of expanding the replacement period of overhead line, it is necessary to
develop methods to predict local wear of contact wire. We aim to bring the rational maintenance on our
daily work by analyzing high frequency data measured by operating train.
1. Introduction
If overhead lines equipment is broken, much time for the repair is needed. It results a large-scale
transportation interruption. We have to grasp the condition of overhead line by various inspections
regularly. One of these inspections includes measuring of contact wire on track inspection car applying
the laser beam technology. The conditional lines measuring on the inspection train is operating 4 times
a year. From this measured data, maintenance staffs plan the repair and replacement of contact wire.
However, we often replace the wire at an early stage before breaking down because of making decision
of maintenance in a few measuring frequencies. The maintenance cost of electrification infrastructure
was about 20 billion yen a year in 2012. In particular, maintenance of overhead line was 56% of the cost,
and 80% of the maintenance was local wear.
For solving the problem, we are developing an overhead line condition monitoring system to be
equipped on operating train of Yamanote Line. It is able to measure the condition of contact wire and
feeder line connection whenever the operating train runs. The more data, the more equipment condition
could be grasped. And, the more data, the more detail analyzing would be possible.
In this paper, we introduce current measuring of contact wire on inspection train. And, we introduce our
efforts of the overhead line condition monitoring system on operating train and prediction of local wear
by analyzing the monitoring data. For the purpose of rational maintenance management, we are going
to make dimension of maintenance, actually repair, and estimate. The result would be expected
maintenance cost down. We aim to come true deeper
condition based maintenance (CBM).
2. Current measurement by inspection car
In JR East, it is measured condition of equipment
composed overhead line by using an electric and track
inspection car, which we call “East-i”. And, the measured
data manages maintenance of the line equipment on all
Shinkansen lines and conventional lines (Fig.1). The
measured items include wear (residual diameter) of
contact wire, deviation, height, hard spots, and impact of
Fig.1 Electric and track inspection car for conventional
Lines (East-i)
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pantograph. Moreover it is measured interval distance
and length of both lines in parallel zone or cross point.
And, these measured values are recorded continuously
as the condition data of overhead line. However, the
East-i runs only four times a year on conventional lines,
so we are not able to monitor in detail the change of
condition.
It is empirically known that wear is making rapid progress
in local wear of contact wire, and that local wear is
caused by factor such as 1) separation between
pantographs and contact wire, 2) sliding of auxiliary
contact strip of pantograph due to excessive deviation, 3)
hard spot on connection point or connector attached point Fig.2 Main causes of local wear of contact wire based
experienced knowledge
on contact wire. Fig.2 shows these causes of local wear.
The local wear is found from the data processed by the measuring system on East-i. And we simply
judges whether data from the measuring system exceed the threshold for the residual diameter of wire.
From the data, we are not able to find the cause (height, deviation, etc.) that lead to local wear.
Therefore, from the data it is not enough to prevent local wear or reduce the amount of wearing.
If overhead line is cut off, serious operation disruption would occur. So, it is needed to replace overhead
line before the wear reaches the limit. And the replace of the line costs a great deal. If local wear of
contact wire is progressing, several ten meters contact wire is inserted and the both ends of the wire are
connected to the conventional wire. And so, it is possible that the wear of contact wire makes progress
again at the connection point due to connector’s own weight.
For both reasons of risk management and cost reduction, a new maintenance management approach is
needed. That is, the factor causing local wear is determined by analyzing measuring data of contact
wire, repair overhead line, and estimate by measuring again. Fig.3 shows the maintenance
management circle.
Against the background of this situation, we
are developing an overhead line condition
monitoring system equipped on operating
train to obtain high frequency data of
overhead line. We are also studying methods
to predict points of where contact wire wears
and amount of how much wears, based on
the statistical correlation between the amount
of wear and other parameters (height and
deviation of contact wire etc.). The correlation
and tendency of contact wire wear will be
analyzed from past data measured by
overhead line condition monitoring system
equipped on East-i. Improvement of the
prediction is expected by the analysis methods
that have made great technical advances in
recent years.
Fig.3 Maintenance management circle to prevent local wear of
contact wire
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3. Monitoring of overhead line by operating train
From fiscal 2008 to 2013, we conducted running tests
to check a prototype overhead line condition monitoring
(1)
system, which has a function measuring contact wire .
The system was installed on the MUE-Train, a multipurpose test train of JR East. Based on the results of
tests using the prototype equipped on the MUE-Train,
we had developed an overhead line condition
monitoring system equipped on the new type preproduction operating car on Yamanote Line in 2015.
We call the operating series car “E235” and the
monitoring system the operating model.
Components of this operating model are concentrated
in a rooftop unit and in an underfloor unit cabinet, and
the operating model consists of rooftop devices and a
control unit installed under the floor. The control unit is
linked with the rooftop devices and the train control
system. Fig.4 shows block diagram of the operating
model. The operating model automatically obtains on
time information of location (line name, line type, and
kilometer), running speed, and train number. Adding
the information to the monitoring data is made possible
to simplify the onboard devices and achieve unmanned
operation.
The operating model has a function, which is 1)
measuring the mostly same data item as East-i, 2)
recording the data in the onboard unit under the floor,
3) transferring the data to ground terminal in
maintenance office. In addition, the operating model
also has a function of giving the alarm when an
abnormal condition is detected. Table 1 shows the
classified table of the function of the operating model.
Fig.4 Block diagram of overhead line condition monitoring
system equipped on operating train
Table 1 Functions of overhead line condition monitoring
system equipped on operating train (operating model)
Sensor
Pantograph
accelerometer
Optical
sensor
separation
Pantograph
monitoring camera
Contact wire height
and
deviation
detector
(Rotary
laser device)
Contact wire wear
detector
(infrared
LED device)
Detected item
Detects impact of pantograph
with
metal
fittings
and
obstructions
Detects arcs generated when
pantograph
separates
from
contact wire
Checks status of pantograph
contact with contact wire
Measures height and deviation
of contact wire
Measures contact wire wear
(residual diameter) and detects
electric poles
Because the operating train repeatedly runs, the
operating model is able to measure high frequency data,
which is the mostly same data item as East-i. We
expect that it is possible to identify in detail changes in
the condition of contact wire from high frequency data.
Consequently, the identification should bring to analyze
causes of local wear of contact wire, which could lead
to deterioration of the overhead line.
In 2016, E235 is going to run as business on Yamanote
Line, where the car runs on the same section up to max
17 times a day. We expect to obtain data hundreds of
times more frequently than data measured by East-i.
Fig.5 Outside of the operating model new operating train,
E235 on Yamanote Line
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We are planning to verify the effects of more high frequent data acquisition. Fig.5 shows outside of the
operating model on E235. In the following, we describe the
measurement system.
3.1 Contact wire condition detector
Fig.6 shows the picture of the pantograph with
accelerometer, UV arc detector (optical separation sensor),
and isolation unit, which extracts the data from high voltage
part. The detector has a function to detect in real time the
pantograph impact or the separation between pantograph
Fig.6 Contact wire condition detector
and contact wire, which is occurred by abnormal condition
in overhead line system. The detector also has a function to automatically issue an alarm by radio to the
maintenance-related departments as soon as abnormal condition is detected.
3.2 Measuring device of contact wire wear, height, and deviation
About the measuring device installed on East-i, the height of contact wire is measured by applying a
potentiometer linked to vertical movement of pantograph, and the wear and deviation is measured by
detecting a reflex of laser beam. The device is so complex and large that the components of the device
are installed not only on East-i rooftop but in East-i. However, the measuring device on operating train,
they need to be simple and compact because it is not allowed to occupy the components in the train. So,
it was not able to install the same device as East-i to E235.
That is, the specification of the detectors is demanded that it is not an obstacle in the cabin, and that the
size is installed onto the train rooftop within the rolling stock clearance. So, we have adopted a smaller
laser positioning device to measure the height and deviation of contact wires. With four synchronized
laser positioning devices placed in parallel, the detector can have a quarter intervals of one device, and
be more compact-sized. Further, the height and deviation
detector need no bodily protection to laser beam emission
because the detector is able to use small intensity of laser
beam of the model categorized as class 1.
The wear detector is used high-intensity infrared LEDs as
the light source, and measured by detecting the reflection
from contact wire. The detector also needs no bodily
protection to laser beam emission. Fig.7 shows the picture Fig.7 Measuring device of contact wire wear, height,
and deviation
of the detectors.
3.3 RFID tag with sensor and reader
We have developed a RFID tag with a sensor and a reader as the
device which collects data for maintenance efficiently from the
sensor installed along a railroad track. The tag with sensor is
supplied the power with which a photovoltaic panel and an electric
double layer capacitor are combined. If electromagnetic power wire
Fig.8 RFID tag with temperature sensor
were to be used, the tag would be too large to be attached on feeder
on DC 1.5 kV feeder line
line. Fig.8 shows the picture of the tag on an aged feeder connect
joint. We estimate that this RFID tag could function for 10 years continuously. Because this tag is
installed in the high-voltage line, the measured value is transmitted by radio at small power.
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The specification of the radio communication of the tag with sensor is based
on IEEE802.15.4. But, a protocol has developed originally, and it isn't based
on the so-called ZigBee standard specification. The protocol is designed that
the measured data is received into a reader equipped on a train which runs at
most 130 km/h speed.
About the reader, we have also equipped this device on E235. Fig.9 shows
the picture of the reader antenna on the roof of E235. The antenna receives
data measured by a RFID tag with sensor, and the data transfers through Fig.9 The reader antenna on
E235 for data from RFID tag
control unit in E235 to ground terminal in maintenance office by radio. The
schematic diagram is shown in Fig.10.
Fig.10 Schematic diagram of data in RFID tag
Fig.11 Data of Contact wire wear, deviation, and height
measured by E235 and East-i
3.4 Data measured by the monitoring system
Fig.11 shows the data measured by the operating model equipped on E235. The data is indicated
contact wire wear, deviation, height. And the same data measured by East-i is indicated in this figure.
We compared the two of data, and found they were almost similar, but the data measured by E235
included more noise than one by East-i. It is because the data by E235 is the raw value which is not
processed noise-cut. The other side, we convince that the noise would be cancelled by acquiring high
frequency data, that is, the more data, the less variable of data is, and the error in the data is smaller.
We are going to estimate high frequency data further.
4. Prediction of the local wear amount of contact wire
4.1 Analysis data
We expect to be able to find unknown correlation and regularity from various big monitoring data of
overhead line by applying the latest data analysis technologies. This is related to expand in addition to
proving the generation mechanism of local contact wire wear based on analysis results instead of an
empirical assumption.
First, we tried to select out local-wear-generating factors that was measured by East-i. In this effort, we
set the measured data and its secondary progressing data to the explanatory variables. These variables
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are shown in Table 2. And we set local wear amount of contact wire in the point, where was indicated
attention by East-i, to the objective variable.
4.2 Problems in data analysis and further efforts
We observed some differences of individual data measured at three months intervals by East-i. We
found cases, which the residual diameter of contact wire was increasing over time instead of normally
decreasing (wearing). And we found data containing noise, which was irregular reflection noise of laser
beam due to rough surface of contact wire damaged by pantograph contact strips. Furthermore, we
found data containing positioning error attributed to incorrect measurement position whenever East-i run,
due to miss-detection of electric poles and dynamic variability of wheel diameter counting kilometer. As
the result, the predicated value of contact wire wear is different from the practice value.
For solving these problems, we considered a data mining, which was the way of cleaning noise and
corresponding each measurement position. And so, it was possible to bring predicted wear waveform
close to an actual measured waveform as shown in Fig.12. In this figure, we calculated predicted
waveform based on measured value in a year and half ago, and we compared between the predicated
waveform and the measured waveform. The both waveforms were identical mostly and we convinced
that the prediction method was improved. We are planning to analyze the high frequency data by E235
from now on. We are verifying that it would be shown the improvement of the prediction precision. If the
improvement is realized, the reasonable maintenance of overhead line would be advanced greatly.
Table 2 List Data Analyzed (selected)
Explanatory variable
Details or example
Structure of
Simple catenary, compound catenary,
overhead line
integrated catenary,
Type of contact wire GT-Sn110º, GT-M-Sn170º, etc
Height
Height of contact wire above track surface
Height variance
Height variance of latest three
measurements
Wear
Residual diameter contact wire
Wear difference
Wear differences before each of latest
three measurements and current
measurement
Dynamic deviation
Deviation of contact wire from center of
track
Gradient
Gradient of contact wire between span
Hard spot
Vertical impact acceleration of pantograph
Pantograph impact
Impact acceleration of pantograph in track
longitudinal direction
Train speed
Train running speed
Fig.12 Result compared predict data with measured data
by cancelling noise
4. Conclusion
JR East has been mainly managing contact wire wear based on data measured by East-i. This is one
example of CBM in railway electrification infrastructure. It is forecasted in near future that it would be
coming the time of decrease of maintenance engineers and maintenance cost reduction. However, it is
requested the more safety and more economic efficiency in maintenance management. For solving
these problems, it will be necessary to deepen CBM and innovate drastically the style of maintenance
work for electrification infrastructure. We are advancing development of the innovation scheme to utilize
collected data for decision-making of maintenance, which we call the “Smart Maintenance Railway”.
Reference:
1) A.Takahashi, T.Kishi, H.Yamamoto, “Overhead Contact Line Monitoring and Prediction of Contact
Wire Localized Wear Points”, JR EAST Technical Review No.29 P22-P25 (2014)
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