Research on Rail Potential While Many Trains Are Starting at the
Same Time
Jie Hao
1, a
, Chuyan Xi
2, b
, Xinyuan Liu
1, c
, Huiping Zheng
1, d
, Ying Qu
1, e
and Yifan Zhang
1, f
1
State Grid Shanxi Electric Power Research Institute; QingNian rd. no.6;Taiyuan;China
2
State Grid Taiyuan Power Supply Company; BingZhou North Rd. NO. 89;Taiyuan;China
e
quying20090244@163.com,
f
358465506@qq.com
Keywords: Traction current; many trains; start; rail potential.
Abstract: The value of traction current affects rail potential. In real life, if many trains start at the same time, the traction
current may increase, and so is the rail potential. The excessive rail potential would seriously threaten people’s
lives. The paper states briefly that many trains start at the same time will increase the traction current and the
rail potential, and it is verified by the Matlab/simulink model and the field test data. Lastly, an optimization
measure of traction current based on locomotive schedule is proposed to reduce the rain potential.
1 UNTRODUCTION
The rapid development of urban rail transit brings a
lot of convenience to people. However, some new
problems such as stray current corrosion and high
orbital potential were on the way. Once the rail
potential is too high, people will have electric shock
hazard. Therefore, the reason of studying orbital
potential, which proposes the inhibitory measures of
orbital potential is particularly important.
Research shows the magnitude of locomotive
traction current can affects the height of orbital
potential. With larger locomotive traction current
comes higher orbital potential (YANG Gang, 2010).
In real life, different execution mode of locomotives
can affects the size of traction current. When the train
is in an accelerated stated, absorbing current from the
power grid. When multiple columns of locomotive
starts at the same time, also causes the increase of
traction current (WANG Jia, 2012).
2 UNDER CERTAIN CONDITION
OF MULTIPLE LOCOMOTIVES
START AT THE SAME TIME,
THEORETICAL
CALCULATION AND
ANALYSIS OF TOTAL
TRACTION CURRENT SIZE
Regard the time of the first locomotive left the
departure station as zero hour, set the traction current
which comes from the locomotive’s parking time at
each station are all zero seconds to i(t,0), where t is
the running time. According to the actual situation,
the duration of the locomotive’s stay at each station
can be adjusted (LI Guoxin, 2010). Assume the time
range of the locomotive’s adjustable action at the
No.m station is [a
m
, b
m
] seconds, the traction current
for the first vehicle at this time can be expressed as
11
(, ) (, )
f
tT itT
(1)
In this formula,
12
1111
[ , ,... ]
N
Tttt
is the vector of
the residence time of the first vehicle at each station.
N is the total number of stations,I (t,T
1
) is a function
about time and locomotive traction current based I
(t,0) on and T
1
. The Fixed D-value to i(t,0) can be
made in accordance with the parking time per station
at the time of the specific calculation. (Because the
Hao, J., Xi, C., Liu, X., Zheng, H., Qu, Y. and Zhang, Y.
Research on Rail Potential While Many Trains Are Starting at the Same Time.
DOI: 10.5220/0010009400170021
In Proceedings of the International Symposium on Frontiers of Intelligent Transpor t System (FITS 2020), pages 17-21
ISBN: 978-989-758-465-7
Copyright
c
2020 by SCITEPRESS Science and Technology Publications, Lda. All rights reserved
17
locomotive lighting, signal, door and other systems
are still in working condition when parking, the
traction current is not zero).
Set the departure interval to n seconds, the
traction current of the P vehicle can be expressed as
(, ) ( , )
p
pp
f
tT it pnT
(2)
Set the maximum number of locomotives running
at the same time on the running route is P, these steps
allow you to get the total current value of the whole
line at any time.
1
(, ) (, )
P
p
p
p
f
tT f tT
(3)
As the locomotive quickened its advance, it
absorbs electricity from the grid. Therefore,
(, ) 0
pp
ftT
. According to formula (3), when there
are multiple locomotives increase the speed of start-
up at the same time on the line, the total traction
current will be increased (M. Brenna, A. Dolara,S.
Leva, D, 2010).
3 MATLAB/SIMULINK
SIMULATION ANALYSIS AND
FIELD RECORD DATA
WAVEFORM VERIFICATION
This article selects the “Rail-Exhaust network-
Groung-Buried metal” model that is closest to the
actual. Separately in One-way Feeding style and
Two-way Feeding style, making simulation analysis
to the model, used to study the effects to rail potential
under a certain state when multiple locomotives
increase the speed of start-up at the same time.
(1) “Rail-Exhaust network-Groung-Buried
metal” equivalent circuit when in the One-way
Feeding style as shown in the figure 1:
机车1 机车2
钢轨
排流
大地
埋地
DC
Rg
Rp
Rd
Rm
Rpd
Rdm
Rgp
+
I
Figure 1: Equivalent circuit under unilateral power supply.
Combining with the actual situation, setting
simulation parameters: Set the 3 substation spacing to
a power supply range, then establish a power supply
range.
Take part of the parameter to a specific value:
DC=750V, Rail longitudinal resistance=0.03
km
,
Earth longitudinal resistance=0.001
km
, Exhaust
network=0.001
km
, Buried metal longitudinal
resistance=0.005
km
, Transition resistance
between track and exhaust network=15
km
,
Transition resistance between the exhaust network
and the earth=3
km
, Transition resistance between
the earth and buried metal=3
km
.
Replace the the locomotive with the controlled
current source, refer to relevant information (M.
Brenna, A. Dolara,S. Leva, D, 2010), set the absorbed
current curve during locomotive operation, as shown
in the figure 2:
015105203530
25
504540
-800
-600
-400
-200
0
200
400
600
800
加速 惰行 刹车
停车
t/s
I/A
Figure 2: Diagram of the absorbed current by locomotive
during running.
Because this paper mainly studies the influence of
track potential when locomotive speed up startup,
choose a simulation time of 0 to 25 seconds, to ensure
that locomotives operate faster during this time
period.
Regard the position of the substation is 0(
0kmL
). Locomotives begin to accelerate from
0kmL
at zero of the relative time, the locomotive
starts to accelerate at a
1.2kmL seconds later,
mapping within the same coordinate system. When
two locomotives are individually accelerated and
simultaneously accelerated, a curve in which the
orbital potential changes over time at a certain point
of
0.6kmL
in the interval as shown in the
following figure 3:
FITS 2020 - International Symposium on Frontiers of Intelligent Transport System
18
??1????
??2????
???????
0
5
10 15 20
-144
-143
-142
-141
-140
-139
-138
-137
-136
-135
t/s
U/V
Figure 3: Diagram of the rail potential located at
0.6kmL
changing by time when two locomotives
accelerate separately and simultaneously.
(2) Equivalent circuits in “Rail-Exhaust network-
Groung-Buried metal” model under bilateral are
shown in the figure 4:
机车1
钢轨
排流网
大地
DC1
Rg
Rp
Rd
Rm
Rpd
Rdm
Rgp
DC2
埋地金
机车2
+
+
I
1
I
2
Figure 4: Equivalent circuit under bilateral power supply.
Parameter settings are the same as parameter
settings under unilateral power supply mode.
Set the location of substation 1 is
0kmL . The
first vehicle speed up from
0kmL at the moment
of relative time, the locomotive starts to accelerate at
3.6kmL in 25 seconds. Mapping within the same
coordinate system, when two locomotives are
individually accelerated and simultaneously
accelerated during operation, the change curve of
orbital potential at a certain point of
1.8kmL in the
interval is shown in the figure 5 respectively:
??1????
??2????
???????
0
5
10 15 20 25
t/s
-240
-230
-220
-210
-200
-190
-180
-170
U/V
Figure 5: Diagram of the rail potential located at
1.8kmL
changing by time when two locomotives
accelerate separately and simultaneously.
Comparing the above modes of power supply, it
can be seen from the waveform diagram of the
influence of locomotive startup acceleration
operation on rail potential, when two locomotives
accelerate operation at the same time, relative to the
case of each locomotive running alone, the orbital
potential will all increase, there’s just a difference in
a value. Therefore we can conclude that the
simultaneous start of the train will cause the traction
current to increase, which causes an increase in
orbital potential.
The following is a waveform based on the
measured data in the field. In both cases, when a
locomotive starts to accelerate operation and multiple
locomotive start to accelerate operation at the same
time, the curve of orbital potential changing with time
at a certain point along the route is shown in the figure
6 and 7:
Figure 6: Diagram of the rail potential located at a point
changing by time when one locomotive accelerate.
Research on Rail Potential While Many Trains Are Starting at the Same Time
19
U/V
Figure 7: Diagram of the rail potential located at a point
changing by time when several locomotive accelerate.
Comparing figures 6 and 7, we can see that the
orbital potential increases when multiple locomotives
accelerate operation at the same time, as opposed to a
single locomotive starting the accelerated operation
alone.
Therefore, in order to reduce the orbital potential,
we can adjust the locomotive scheduling time,
reducing the probability of simultaneous start-up
operation of multiple locomotives, making some
optimization of the traction current.
4 OPTIMIZATION OF
TRACTION CURRENT BASED
ON LOCOMOTIVE
DISPATCHING
When the locomotive is running, the residence time
of the locomotive at each station can be adjusted
according to the allowable range. Therefore, the time
of station stay along the route can be reasonably
optimized to reduce the simultaneous start-up
operation probability of multiple locomotives.
According to the above ideas, traction current
optimization based on locomotive dispatching can be
realized by the following two methods:
1) Calculate the total value and take the minimum.
For each set of locomotives can be achieved at each
station residence time, Calculating the corresponding
scheduling schedule separately, and using it as the
final scheduling schedule. Due to the long running
time of the locomotive throughout the day, the
calculation of this method is too heavy, so it’s not
feasible.
2) Establishing the mathematical model of using
locomotive residence time to reduce total traction
current, solving the minimum values. At the same
time, up to
M
P
n
(4)
Locomotives were running at the same time, in
the above formula, M is the maximum time allowed
for a locomotive from the point of departure to the
end, and N is the fixed departure interval for
locomotive dispatching. Also, from the beginning of
the P-1 vehicle, a loop is formed at the NP time
interval, so it is calculated only within the [N (P-1), N
(P-1) +NP] time frame. Make the running schedule of
the P vehicle, and the subsequent locomotives
recycling uses this schedules.
The impact model used to reduce the total traction
current by adjusting the residence time of each station
can be expressed as:
min max{ ( , )}
f
tT
Tt
(5)
.. ( 1) (2 1)st n P t n P
≤≤
(6)
mm m
p
atb≤≤
(7)
1
M
m
p
m
tc
(8)
In formula (8), C is the maximum allowable time
for stays along the locomotive, which is a nonlinear
and extremely small problem. By calculation, the
value of the minimum traction current can be solved.
5 CONCLUSION
Based on the actual situation, this paper establishes a
“Rail-Exhaust network-Groung-Buried metal” four-
layer model, and under the two power supply modes
of unilateral power supply and bilateral power supply,
the model is simulated and verified by the actual test
data, and the results show that the rail potential is
increased by the simultaneous start-up operation of
multiple locomotives. By establishing the
mathematical model of locomotive residence time to
reduce the total traction current, it is a measure to
reduce the rail potential by reasonably optimizing the
station residence time along the locomotive.
FITS 2020 - International Symposium on Frontiers of Intelligent Transport System
20
REFERENCES
LI Guoxin. Analysis of DC Traction Reflux System and
Research on Related Problems in Rail Potential. China
University of Mining and Technology Doctor Degree
Thesis,2010.
M. Brenna, A. Dolara,S. Leva, D. Zaninelli. Effects of the
DC stray currents on subway tunnel structures
evaluated by FEM Analysis. IEEE, 2010.
WANG Jia. Study On Distribution Of Metro Stray Current
Based On Multi-locmotive Operation. Southwest
Jiaotong University Master Degree Thesis,2012.
YANG Gang, LIU Mingguang, LI Nan, QU Zhijian.
Research on Model of Rail Potential Distribution and
Its Simulation. Journal Of Beijing Jiaotong University,
2010, 34 (2).
Research on Rail Potential While Many Trains Are Starting at the Same Time
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