地铁
合肥共达职业学院-幼儿园教师培训计划
An
Adaptive Protection Scheme in Subway
DC
Traction Supply System
Zhu Panfeng,
Li
Yongli
Abstract-- The protection of
DC traction supply system
plays a very
important role in guaranteeing the safety and
reliability of DC traction supply system for
subway vehicles. It
should trip the fault
installation selectively and quickly when
the
fault occurs. Therefore, by establishing a
mathematics
simulation model of DC traction
supply system matching the
actual metro state,
it provides theoretical basis for studying
the
principle of the protection, scheme configuration
and
setting the fixed value. And through
analyzing the typical DC
traction supply
system 'of subway and its simulation
calculation, an adaptive microprocessor-based
protection
scheme in DC traction power system
is
presented.
Keywords-adaptive, DC
traction
Microprocessor-based protection.
supply system
.-
i
1
.
IIOKV
.-.
-.,
'
Main
transformer
35KV
1
).,
-<.-
.
Traction
translormer
(,
_'
~
~
Rectifier
unit
4
.-
i
--.
1
!'--)
(__.)
_- (
Step-down
-
-.
1'
,.
I
.
I)_
transformer
$$
(
7i
,)
Fig.2 Subway Power
System
electric elevator, transmission and
other dynamic
equipment, automaticlequipment
and the illumination of the
station.
Power
system and traction power supply system consist
of several parts as follows: upper power
supply substation,
traction substation,
rectifier unit and step-down substation.
The-
upper power supply substation is a main station,
along
the subway route, which is built
according to the power
I. INTRODUCTION
ith
the fast development of economy in China, the
traffic passenger volume increases
continuously.
Presently, more than 20 cities
are planning to develop
subway. It is urgent
needed to develop the subway
protection
devices with high performance and reliability.
To trip the short circuit default only by
instantaneous
protection and overcurrent
protection seems not satisfactory.
With the
development of electronic technology and
computer science, the protection based on the
rate of
current increase has been implemented
by microprocessor.
To
a
certain
degree, the reliability
and
accuracy
of
the
protection are improved. But
the difficulty is also
encountered to
distinguish between the starting current of
vehicle and the
short
circuit current.
11.
ANALYSIS
OF
TYPICAL MODE
OF
SUBWAY SUPPLY
W
I
1
35KV
I
i
I
nni
The
structure of DC traction supply system in subway
is
complex, thereby a lot of factors should be
taken into
account. The paper begins with
establishing the
mathematical model of DC
traction supply system,
sequentially the
simulation calculation is proceeded with.
The
power supply system in subway is an important
part.
Synoptically, the subway power supply
system is composed
of three parts, that is,
power system, traction power supply
system,
supply system for dynamic and illuminating system.
The traction power supply system consists of
traction
substation, conductor rail, and the
subway train. The
dynamic and illuminating
system are responsible for
supplying power for
the facilities, such as fans, water pump,
Zhu
Panfeng is with the Department of Electrical
Engineering'Tianjin
University, Tianjin
,
China (e-mail: zhupf@).
Li Yongli is with
the Department of Electrical Engineering, Tianjin
University, Tianjin
,
China (e-mail:
lyl519@).
0-7803-7459-202$$17
00
(ci
2002 IEEE
+I
5nnv
I,ne
reflux
IlllP
1
eontacr
TPflll.
llllt-
llW
Fig2 Typical DC
Traction Supply System
demand and the subway
length. The main station is
generally at llOKV
AC
as shown in Fig.1. There are
several traction substations of 35KV
AC
established along
the subway route. The
typical connecting diagram
of
traction
substations is shown in Fig2. The Bus of 35KV is
-
716
-
led to the
rectifier units through interconnection, switch.
In
A.
Each vehicle starts at fixed
interval.
this way 35KV voltage is stepped
down by rectifier
transformer, and the output
is DC voltage. Through positive
B. Each
vehicle runs
from
start station to
terminal station
switch NC
1
1,
NC
12 and negative switch NB 1 1, NB 12, DC
t1500V
is conveyed to positive bus and
negative bus. The positive
1
bus is
connected to contact line by DC feeder switch
NC21,
I
I
I
I
NC22, NC23,
NC24, while the negative bus is connected to
the rail track by reflux line. According to
the related
standards of underground metal
conduit pipe, the negative
bus
of
subway traction substation is ungrounded and
rail
track insulated to ground. In general,
there are two voltage
levels for the overhead
contact line: 750VDC and
I
I
I I
I
1500VDC(in the paper, the traction power
system of
1500VDC is studied.)
Fig.5 The
Unit Work Mode of Motors
to repeat the same
physics process.
C.
The current
of
the contact line corresponds with the
time-variant distance
of
the vehicle.
D.
The stopping time
of
all
vehicles is identical.
Because
of
GTO
interrupter of the vehicle, the train can
be
controlled to run according to the operational
sketch.
That is to say, the variation of
velocity corresponding to the
time can be
taken as
known
value.
So
the
simulation model
of the time-variant network
of
the traction power supply
system
varies periodically. We only need to study the
variety pattern
of electrical parameter in
one cycle.
Establish the mathematics model of
vehicle:
Based on the knowledge of motors, we
give out the
potential transient balance
equation:
7--
Urn
=
C,$$n
+
I,R
i-
L-
dIm
dt
In the
equation,
Um: motor voltage
Ce: a constant
of counter-electromotive force
4
:
main magnetic flux
n: rotational speed of
DC motor
I,,,: motor current
Fig.3 Train
Operational Sketch
L:
motor inductance
Due to time-variant movement of the power
vehicle, its
R:
resistance of motor
circuit
position and current are the time-
variant function. Hqwever,
This paper takes a
train organizing 4 drive units and 2
because
the vehicle is always requested to run accurately
to
trailer units into a group for example.
Each drive unit is
+,I--+
il
1,
FII:I:;rl+lll:t
I
k:,:,:,,,t
.,,,
It
li,,,i
I:
I-
h
kll
F,,
.-tIIIX
I,,?+
F
'.+!llx
itlIc
Fig.4 Electric Circuit Model of
Traction Network
the operational sketch,
so
it appears regular for the
operational state and the state of power
supply at a certain
interval. For the sake
of the convenient for analysis, the
paper
makes such premises without losing accuracy as
follow:
-717-
traction power
system, we can attain the calculated
simulation model of DC traction power supply
system of
subway, as shown in Fig.6. According
to
the electric circuit
theory, we can
get such equations as follow:
9'
=
('d
+
'contuctlme
+
'refluhe)
1'
+
2um
$$
3-
2
5
1)
2.'
SI,,
=
I,
+I,
Refering
to the known 4
--I
curve, the electric
parameters
such as the start current of the
vehicle and the short circuit
current can be
derived to study their rule of variety.
Through simulating calculation, the results
are described as
follow:
A.
At the
moment when the train starts up, the rate
of
current increase reaches the maximum value,
however the
rate diminishes gradually with
time being, as shown in
8.
Fig.
7
and Fig.
0.5
-
0-
-0.5
0
0.5
1
1.5
2
2.5
3
3.5
4 4.5
s
Fig8 The Derivative
Curve
of
Start Current
I1
2.5
B.
Although the maximum values
of
the start current and
the short circuit
current are close at value, the increase
of
short circuit current is almost instantaneous
to reach the
maximum value while the start
current needs
a
certain time
9. to
achieve maximum,
as
shown in Fig.
1.5
Iv.
THE
ADAPTIVE
METHOD TO
DISCRIMINATE THE START
CURRENT
OF
VEHICLE AND THE SHORT CIRCUIT CURRENT
OF
THE TRACTION
SUPPLY
SYSTEM
It is
critical for the protection of DC traction supply
system of subway to discriminate the increase
of start
current of vehicle and the jump of
short circuit current.
Through simulating
calculation, it is found that the rate of
start current increase in a short time is
quite great when the
train is heavy-loaded.
Presently, many DC subway
protections
discriminate the start current
of
vehicle
and the
short circuit current by judging the
rate of current increase
dIdt and the current
increase
A
I. However the settings,
based on this principle, are difficult to
determine. If the
settings of dIdt and
A
I
are a little bit bigger, when the
Is
60s
61s
Fig9 The Short Circuit Current
Curve (short circuit after 60s
1
due
to the insufficient sensitivity. Otherwise if the
values of
dIdt
and
A
I
are
quite small, when the train starts, the
protection maybe maloperate. Through
simulating
calculation, we know that, even
though the rate of line
current increase is
great with the vehicle starting, but the
current reaches the peak value after
a
certain time, and
decreases subsequently.
However, the rate
of short circuit
short
increase is great.
So
the protection trip
depends on the
integral value. There is a
blocking condition, that is, if the
average
current value in the integral time is less than
the
maximum current, the protection should be
lockout, as
shown in Fig.
10.
Because
the electric measurement of the protection is
DC, the integral time may be very short and
the curve of
protection operation is time-
inverse characteristic. When
the short circuit
current is greater, the trip time is shorter.
So
the protection may trip without time
delay if the short
circuit default occurs near
the traction substation.
Otherwise it is on
the contrary. When the start current of
the
heavy-loaded train is approximate to the short
circuit
current
of line, the start current
is non-constant and it rises
0 05
1
15
2
25
3 35
4
4!
slowly and
decreases continuously after achieving
s
maximum. Though the maximum of start current
is
Fig7 Start Current
I1
Curve
approximate to the short circuit current,
there is time
train is heavy-loaded or short
circuit occurs at the terminal
difference for
the fixed integral value and the current value
of
section, the start current
of
vehicle is quite close to the
variation in
the span.
So
whether average current value
of
i
-
-718-
the
integral time is less than the maximum
of
current can be
taken
as
a
criterion of the protection lockout.
&
’
trip
Li Wei, “Research on real-time
measurements of track continuity
and track-to-
earth resistance of metro,”
Journal
Of
China University
Of
Mining
&
Technology, vo1.30 No.4, pp. 416-420,
Ju1.2001.
Xue Moqing, “Research on real-
time measurements
of
track
continuity
and track-to-earth resistance of metro,” Shanghai
.
Electric Appliance Technology, N0.2, pp.
5-9, 1998.
Liu Shulun,
“
The
transition in process of start of direct current
electric motor,”
Journal
of
Wuling, -vol.
I9
N0.6, pp. 27-29,.
Nov.
1998.
Li Xiaqing, Li Li, Wang
Lihu, “Research and evaluation of high
voltage
direct current power supply plan in electric
railway,”
Engineering Introduce and Management
vol.
11,
No.3, pp.22-26.
Sep.
1998.
I
<
~mx
Books:
[7]
Xu
Shizhang, “Electromechanics”, vol.
2.
Mechanical Industry
Publishing
Company:
1980,
pp
81-130.
Papers
from Conference Proceedings (Published):
v.
THE COMPUTER PROTECTION SCHEME OF
DC
TRACTION
11
definite-time overcurrent
protection
countercurrent
urotection
[SI
Macro Galaverna, Srefano Savio,
Giuseppe Sciutto, Pierluigi Tenca,
and
K.
J.
Roesler,
“
Voltage regulation
of AClDC converters for
railway app1ications:a
comparison among control strategies,”
Proceedings
of
the
1998
IEEE
International Conference
on
Control
Applications,
pp.
1394-1398,
Apr.
1988.
I
1
l-~~j
1
’
trip
VIII.
BIOGRAPHIES
Zhu
Panfeng was born in Shenyang, China, on
Nov.
29, 1976.
He graduated from the Tianjin
University and obtained the B.S. degree in
1998.
Now he is a graduate student
as
a postgraduate in
Tianjin University. His
interest of research is
adaptive protection of
traction power supply
network of subway.
I
under-vol tage protection
protectlon
interlock
I
d
j-’I
I-l+fU
protection
interlock
Fig.
1 1
The Configuration Diagram
of
The
Protection
POWER SUPPLY SYSTEM
By means
of
the adaptive criterion we can .attain
improved microprocessor-based protection
scheme
of
DC
traction power supply
system. The main protection is the
adaptive
principle. The backup protections consist
of
definite-time overcurrent protection,
countercurrent
protection and under-voltage
protection. The breaker at the
opposite can
trip by the protection interlock. The
configuration diagram
of
the
protection is shown in Fig.
1
1.
VI.
CONCLUSION
This paper calculates the start
current curve and the
short circuit current
curve based on the analysis to the
simulation
model
of
the DC traction power supply
system
of
subway. A new adaptive
protection principle
of
DC
traction
supply system is presented to discriminate the
start
current and the short circuit current.
Based on the method, a
microprocessor-based
protective scheme is also proposed.
The scheme
takes the requirements of profective
coodination into account, and the reliability
and sensitivity
of protection for DC traction
supply system are improved
as
a
result.
Li Yongli received the B.S. and
M.S.
degrees
in Tianjin University in
1984
and
1987,
China. In
1993,
she got the Ph.D. from the University libre
de Bruxelles, Belgium. Now, She is the
professor
in Tianjin University. She is the
member of CSEE.
Her research interest is
development of new
protective relays and
control devices applied in
power system using
digital signal processing
techniques.
VII.‘
REFERENCES
Periodicals:
[I]
Wu Zhengkang, and Yang Qihua,
“
Simulation analysis for a short
circuit in
the subway traction power sbpply nerwork,“
Journal
Of
The China Railway Society,
vol. 15 No.
I,
pp.
39-44,
March
1993.
[2]
Liu Xiulin,
”
Development of microprocessor-based
GTO
chopper
control system for Beijing metro,”
Electric Drive For Locomotive.
vol3. No3,
1999.
-
71
9