energies
Article
A New Method of Ground Fault Location in
2 × 25 kV Railway Power Supply Systems
Jesús Serrano 1 , Carlos A. Platero 1, *, Máximo López-Toledo 1 and Ricardo Granizo 2
1
2
*
Department of Electrical Engineering, ETS Ingenieros Industriales, Universidad Politécnica de Madrid,
C/José Gutierrez Abascal, 2, Madrid 28006, Spain; [email protected] (J.S.);
[email protected] (M.L.-T.)
Department of Electrical Engineering, ETS Ingeniería y Diseño Industrial,
Universidad Politécnica de Madrid, C/Ronda de Valencia, 3, Madrid 28012, Spain; [email protected]
Correspondence: [email protected]; Tel.: +34-91-336-31-29; Fax: +34-91-336-30-08
Academic Editor: William Holderbaum
Received: 7 December 2016; Accepted: 3 March 2017; Published: 10 March 2017
Abstract: Owing to the installation of autotransformers at regular intervals along the line, distance
protection relays cannot be used with the aim of locating ground faults in 2 × 25 kV railway power
supply systems. The reason is that the ratio between impedance and distance to the fault point is not
linear in these electrification systems, unlike in 1 × 25 kV power systems. Therefore, the location of
ground faults represents a complicated task in 2 × 25 kV railway power supply systems. Various
methods have been used to localize the ground fault position in 2 × 25 kV systems. The method
described here allows the location of a ground fault to be economically found in an accurate way
in real time, using the modules of the circulating currents in different autotransformers when the
ground fault occurs. This method first needs to know the subsection and the conductor (catenary or
feeder) with the defect, then localizes the ground fault’s position.
Keywords: ground faults; protection; 2 × 25 kV; fault location; railways
1. Introduction
Currently, the most widely used electrical configuration to feed high-speed trains is the 2 × 25 kV
railway power system. The use of this system, compared to the traditional 1 × 25 kV railway power
system, allows the required number of traction substations erected along the line to be reduced, because
it has lower losses and lower voltage drops along the line [1].
In this 2 × 25 kV system, each traction substation feeds two sections, one in each direction
of the line. Each section consists of several subsections of similar length that are delimited by
autotransformer power stations (ATS). These autotransformers have two terminals; one is connected to
the positive conductor rated 25 kV (catenary), while the other is connected to the negative conductor,
also rated 25 kV (feeder). The midpoint of its winding is connected to the rail and ground. Another
autotransformer (SATS) is installed at the end of the section and is connected in the same manner as
the intermediate autotransformers (Figure 1).
Electrical installations need adequate protection to ensure a reliable and safe operation [2]. This
need is accentuated in the case of electric railway traction systems due to the increased number of
failures caused by the sliding of the pantograph on the contact wire, which can cause its breakage.
These faults cause severe economic and social problems by disrupting rail services. Therefore, it is
very important to detect and locate the point where the ground fault has occurred in order to isolate
the subsection at the fault, and to repair such a failure as quickly as possible [3].
In AC electrical traction systems, the most-used method for measuring the distance from a traction
substation to a ground fault due its stability, reliability and simplicity, is the impedance method [4,5].
Energies 2017, 10, 340; doi:10.3390/en10030340
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Energies 2017, 10, 340
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However, in 2 × 25 kV traction power systems, it is not possible to determine the distance from the
traction substation to the ground faults in an acceptable manner with this method [6]. This is due to
the presence of autotransformers that make the ratio impedance-distance nonlinear [7].
To be able to use this location method and to know the distance to the ground fault through the
impedance seen from the traction substation, it is necessary to disconnect the autotransformers and
separate the catenary from the feeder circuits when a ground fault is detected. Thus, the subsection
is divided into two circuits with only one conductor and return cable, as in the case of 1 × 25 kV
systems. Following this procedure, a ground fault can be located by measuring the impedance in each
conductor and return cable circuits. This method is used in some 2 × 25 kV traction power systems,
but it is very slow, requiring several operations of connection and disconnection of switches with
waiting times between each maneuver [8,9].
Another traditional method used for fault location in railway power systems that employs
auto-transformers is the AT neutral current ratio fault location method [10]. However, the capacity
of the main transformer is much higher than that of the autotransformer stations. For this reason,
this method can be insufficiently accurate and identifies failures in the wrong subsections. Therefore,
a method of compensation using the neutral currents circulating in adjacent autotransformers to those
of the faulty section was proposed in [11].
The location method using travelling waves, in addition to transmission and distribution lines,
has been applied to the lines of railway traction power systems, aided by advances in the theory of
wave propagation, microelectronics and data processing [4]. In this method, when a ground fault
occurs, there are various types of technologies to locate ground faults according to the detection of the
generated travelling wave at one end [12] or at both ends [13], and if it is performed by the wave itself
or by a pulse injected into one end when such a fault occurs [14]. However, this method is difficult to
implement because of its limited reliability, complex setup and high economic investments [15]. This
difficulty is due to the specific characteristics of traction facilities with numerous discontinuities in the
contact line and multiple loads changing position continuously [16].
This article describes a new ground fault location method that allows the position in the railway
line where a ground fault has occurred to be obtained in real time, and also whether it has been in the
catenary (positive conductor) or feeder (negative conductor). The method locates the position of the
failure using the values of the modules of the currents in different autotransformers when a ground
fault occurs, and is based on the knowledge of the subsection and the conductor where the ground
fault has occurred following the method described in [17]. The method that identifies the subsection
with a ground fault is summarized in Section 2. In Section 3, the distribution of currents in the
autotransformers is presented for different ground fault locations by computer simulations. Section 4
describes the principles of the new method for ground fault location. In Section 5, the experimental
results of tests carried out in the laboratory are introduced. Finally, Section 6 summarizes the main
contributions of the paper.
2. Brief Description of Ground Fault Identification Method for 2 × 25 kV Railway Power
Supply Systems
Figure 1 shows the simplified scheme of an electric section that is fed by a 2 × 25 kV power system
with three subsections (A, B and C) delimited by intermediate autotransformers ATS1 and ATS2. At the
end of the section, an autotransformer SATS connects the three conductors. Also, the distribution of
currents in the conductors is represented when a train travels in the intermediate section B.
According to [17], when in a line of a 2 × 25 kV rail power system supply, a fault occurs between
the catenary and rail or between the feeder and rail, there is a significant increase in the current
flowing in the windings of the closest autotransformers to the position where the fault has occurred.
In addition, the angles between these currents and voltages between the catenary and rail change at
the location of the autotransformers.
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14
Section
Section
Subsection
SubsectionAA
Subsection
SubsectionBB
33
I
22 I
II
++25
25kV
kV
11
I
22 I
Catenary
Catenary
2I2I
11
22II
II
11
22II
II
Rail
Rail
11
I
22 I
11
22II
11
I
22 I
II
- 25 kV
TS
TSTraction
TractionSubstation
Substation - 25 kV
Subsection
SubsectionCC
ATS
ATS11
ATS
ATS22
Feeder
Feeder
SATS
SATS
Figure
Figure
Simplified
diagram
25
kV
rail
power
system
and
current
distribution
while
train
Figure1.1.
1.Simplified
Simplifieddiagram
diagramofof
ofa a2a 2×
2 ××25
25kV
kVrail
railpower
powersystem
systemand
andcurrent
currentdistribution
distributionwhile
whileaaatrain
train
travels
ininsubsection
B.B.
travels
subsection
travels in subsection B.
The
power
factor
the
high-speed
trains
close
to
the
unity,
the
impedance
seen
from
the
The
Thepower
powerfactor
factorofof
ofthe
thehigh-speed
high-speedtrains
trainsisis
isclose
closeto
tothe
theunity,
unity,soso
sothe
theimpedance
impedanceseen
seenfrom
fromthe
the
autotransformer
is
mainly
resistive.
In
a
line
feeding
trains
in
normal
operation
without
any
faults,
autotransformer
is
mainly
resistive.
In
a
line
feeding
trains
in
normal
operation
without
any
faults,
autotransformer is mainly resistive. In a line feeding trains in normal operation without any faults,
◦.
these
angles
are
close
180°.
these
theseangles
anglesare
areclose
closetoto
to180
180°.
But
ground
fault
arises,
the
impedance
seen
from
the
autotransformer
can
be
the
catenary
or
But
Butifififaaaground
groundfault
faultarises,
arises,the
theimpedance
impedanceseen
seenfrom
fromthe
theautotransformer
autotransformercan
canbe
bethe
thecatenary
catenaryor
or
feeder
inductance.
So,
the
angle
between
currents
and
voltages
in
the
autotransformers
closest
to
the
feeder
inductance.
So,
the
angle
between
currents
and
voltages
in
the
autotransformers
closest
to
the
feeder inductance. So, the angle between currents and voltages in the autotransformers closest to the
◦ ordecreasing
◦ becausethey
fault
changes
increasing
90°
90°
are
reactive
currents
without
resistance
fault
faultchanges
changesincreasing
increasing90
90°or
or decreasing
decreasing90
90°because
because they
theyare
arereactive
reactivecurrents
currentswithout
withoutresistance
resistance
component.
There
is
mainly
reactive
power
in
the
2
×
25
kV
supply
system.
In
the
case
of
ground
component.
There
is
mainly
reactive
power
in
the
2
×
25
kV
supply
system.
In
the
case
of
component. There is mainly reactive power in the 2 × 25 kV supply system. In the case ofground
ground
fault
between
the
catenary
and
ground,
the
angle
between
the
currents
and
voltages
in
the
fault
between
the
catenary
and
ground,
the
angle
between
the
currents
and
voltages
in
the
nearest
fault between the catenary and ground, the angle between the currents and voltages in the nearest
nearest
◦ . However,
autotransformers
approximately
90°.
However,
the
fault
occurs
between
the
feeder
and
ground,
autotransformers
autotransformersisis
isapproximately
approximately90
90°.
However,ifififthe
thefault
faultoccurs
occursbetween
betweenthe
thefeeder
feederand
andground,
ground,
◦ This last
the
angle
between
currents
voltages
in
the
autotransformers
is
now
last
the
between
thethe
currents
andand
voltages
in the
autotransformers
is now
type
theangle
angle
between
the
currents
and
voltages
in nearest
the nearest
nearest
autotransformers
is270
now. 270°.
270°. This
This
last
type
of
fault
and
the
angles
between
the
currents
and
voltages
in
the
nearest
autotransformers
oftype
faultofand
theand
angles
the currents
and voltages
the nearest
autotransformers
are shown are
in
fault
thebetween
angles between
the currents
and in
voltages
in the
nearest autotransformers
are
shown
Figure
shown2.in
in Figure
Figure 2.
2.
Subsection
SubsectionAA
Subsection
SubsectionBB
VVC1
C1
Subsection
SubsectionCC
VVC2
C2
IIA1
A1
VVC3
C3
IIA2
A2
IIA3
A3
Fault
Fault
Traction
TractionSubstation
Substation
ATS
ATS11
IIA1
A1
ATS
ATS22
SATS
SATS
270º
270º
270º
270º
180º
180º
VVC1
C1
VVC2
C2
IIA2
A2
VVC3
C3
IIA3
A3
Figure
2. Angular
difference between
currents (IA
) and voltages
in catenary
(VC )C)ininautotransformers
Figure
Figure 2.
2. Angular
Angular difference
difference between
between currents
currents (I(IAA)) and
and voltages
voltages in
in catenary
catenary (V
(VC) in autotransformers
autotransformers
with
fault
between
feeder
and
ground
in
subsection
C.
with
with fault
fault between
between feeder
feeder and
and ground
ground in
in subsection
subsection C.
C.
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Therefore, if the currents and voltage values, including the phase angle difference between them,
areTherefore,
measuredifinthe
thecurrents
autotransformers,
a fault
occurs
any conductor
the ground,
and voltagewhen
values,
including
thebetween
phase angle
difference and
between
them,
is possibleintothe
identify
in which subsection
the fault
took
place, and
which conductor
such a
areit measured
autotransformers,
when a fault
occurs
between
any conductor
and thehad
ground,
fault.
it is possible to identify in which subsection the fault took place, and which conductor had such a fault.
3. 3.
Current
Distribution
inin
Autotransformers
forfor
Different
Ground
Fault
Locations
in in
2×
2525kV
Current
Distribution
Autotransformers
Different
Ground
Fault
Locations
2×
kV
Rail
Power
Supply
System
Rail
Power
Supply
System
AsAs
explained
before,
if if
a ground
fault
takes
place
between
thethe
catenary
and
rail
oror
between
thethe
explained
before,
a ground
fault
takes
place
between
catenary
and
rail
between
feeder
and
rail
in in
a power
system
fedfed
byby
2×
the
values
ofof
the
currents
flowing
inin
thethe
windings
feeder
and
rail
a power
system
2 ×2525kV,
kV,
the
values
the
currents
flowing
windings
ofof
thethe
closest
autotransformers
to
the
point
where
the
fault
has
occurred
experience
a
very
significant
closest autotransformers to the point where the fault has occurred experience a very significant
increase.
These
increase.
Thesevalues
valuescan
canbebeeasily
easilyobtained
obtainedby
bymeasuring
measuringthe
thecurrent
currentin
inthose
those windings.
windings.
ToTo
simulate
thethe
current
distributions
in in
autotransformers
when
ground
faults
occur
along
allall
simulate
current
distributions
autotransformers
when
ground
faults
occur
along
positions
of
a
section,
the
circuit
shown
in
Figure
3
was
used.
The
modified
nodal
circuit
analysis
positions of a section, the circuit shown in Figure 3 was used. The modified nodal circuit analysis
method
[18]
is is
applied
to to
solve
such
a circuit
using
MATLAB
(MathWorks
Inc.:
Natic,
MA,
USA).
method
[18]
applied
solve
such
a circuit
using
MATLAB
(MathWorks
Inc.:
Natic,
MA,
USA).
ZC [Ω/km]
VC1
VC2
VC3
Fault
IA1
IA2
IA3
ZR [Ω/km]
ZF [Ω/km]
ATS 1
Subsection A
0 km
ATS 2
Subsection B
10 km
SATS
Subsection C
20 km
30 km
Figure
Simulated
2 ×2525kV
kVpower
powersupply
supplysystem
systemwith
withtwo
twoconductors
conductorsand
andreturn
returngrounded
grounded
wire.
Figure
3. 3.
Simulated
2×
wire.
Fault
in
subsection
C
between
catenary
and
rail.
Fault in subsection C between catenary and rail.
In these simulations, a value of 27.5 kV has been given to each source of alternating current (AC)
In these simulations, a value of 27.5 kV has been given to each source of alternating current (AC)
voltage. The impedance values per unit length of each conductor are listed in Table 1, where ZC is the
voltage. The impedance values per unit length of each conductor are listed in Table 1, where ZC is the
impedance value per unit length of the catenary, ZF is the corresponding impedance of the feeder;
impedance value per unit length of the catenary, ZF is the corresponding impedance of the feeder; and
and ZR is the impedance of the rail that is grounded. Likewise, the values of the mutual impedances
ZR is the impedance of the rail that is grounded. Likewise, the values of the mutual impedances per
per unit length between the catenary, feeder and rail are also shown in Table 1.
unit length between the catenary, feeder and rail are also shown in Table 1.
Table 1. Self and mutual impedance values of railway conductors.
Table 1. Self and mutual impedance values of railway conductors.
Conductor
Conductor
Catenary
Feeder
Catenary
Feeder Rail
Rail Conductors
Catenary-Feeder
Conductors
Catenary-Rail
Catenary-Feeder
Feeder-Rail
Catenary-Rail
Feeder-Rail
ZC
ZZCF
ZFR
Z
ZR
ZCF
ZCR
ZCF
ZFR
ZCR
ZFR
Self-Impedance Ω/km
Self-Impedance
0.1197
+ j0.6224 Ω/km
0.1114
+ j0.7389
0.1197
+ j0.6224
0.0637
+ j0.5209
0.1114
+ j0.7389
0.0637 + j0.5209
Mutual Impedance
Ω/km
0.0480 Impedance
+ j0.3401 Ω/km
Mutual
0.0491 + j0.3222
0.0480 + j0.3401
0.0488 + j0.2988
0.0491 + j0.3222
0.0488 + j0.2988
The values of the impedance parameters of the transformer of the substation and of the
autotransformers used in the simulation are shown in Table 2.
The values of the impedance parameters of the transformer of the substation and of the
autotransformers used in the simulation are shown in Table 2.
Energies 2017, 10, 340
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Table 2. Transformers and autotransformers ratings used in the simulation.
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Main Transformer
Voltage ratioand autotransformers
400/2 ratings
× 27.5used in thekV
Table 2. Transformers
simulation.
Table 2. Transformers
ratings used in the
simulation.
Rated powerand autotransformers60
MVA
Transformer
Short-circuit voltage Main
10
Main Transformer
%
Voltage ratio
400/2 × 27.5
Voltage ratio
400/2 × 27.5
Autotransformers
Rated power
60
Rated power
60
Short-circuit
voltage
10
Voltage
ratio
55/27.5
Short-circuit voltage
10
Autotransformers
Rated power
15
Autotransformers
Voltage
ratio
Short-circuit
voltage
155/27.5
Voltage ratio
55/27.5
Rated power
15
Rated power
15
Short-circuit voltage
1
Short-circuit voltage
1
kV
kV
MVA
MVA
%
kV
%
MVA
kV
%
kV
MVA
MVA
%
%
This circuit has been resolved making faults between the catenary and feeder conductors and rail
This
circuit
has
resolved
faults
between
the
conductors
and
in all positions
the three
subsections
A, B and
C that
compose
the 30and
kmfeeder
section.
Thus, different
This of
circuit
has been
been
resolved making
making
faults
between
the catenary
catenary
and
feeder
conductors
and
rail
in
all
positions
of
the
three
subsections
A,
B
and
C
that
compose
the
30
km
section.
Thus,
different
values of
the
currents
in
the
autotransformers
have
been
obtained
with
ground
faults
at
all
points
rail in all positions of the three subsections A, B and C that compose the 30 km section. Thus, different of
values
the
currents
in
autotransformers
have
been
obtained
with
ground
of
the section
in of
both
fault is between
catenary
and faults
whenat
is points
between
values
of
the cases:
currentswhen
in the
thethe
autotransformers
havethe
been
obtainedand
withrail
ground
faults
atitall
all
points
of the
the
section
in
both
cases:
when
the
fault
is
between
the
catenary
and
rail
and
when
it
is
between
the
the section
in both
cases:
when the
fault
is between in
theFigures
catenary4and
when
it is between
the of
feeder and
rail. The
results
obtained
are
represented
andrail
5. and
Figure
4 shows
the values
feeder
The
obtained
feederI and
and rail.
rail.and
TheIresults
results
obtained are
are represented
represented in
in Figures
Figures 44 and
and 5.
5. Figure
Figure 44 shows
shows the
the values
values of
of
the currents
A1 , IA2
A3 for catenary-rail faults; and Figure 5 shows the values of the currents IA1 ,
the
currents
I
A1, IA2 and IA3 for catenary-rail faults; and Figure 5 shows the values of the currents IA1,
the currents IA1, IA2 and IA3 for catenary-rail faults; and Figure 5 shows the values of the currents IA1,
IA2 andIA2
IA3and
forIA3feeder-rail
faults.
for feeder-rail
faults.
IA2 and IA3 for feeder-rail faults.
7000
7000
IA1
IA1
6000
6000
IA2
IA2
Current[A]
[A]
Current
5000
5000
IA3
IA3
4000
4000
3000
3000
2000
2000
1000
1000
0
00
0
5
5
10
10
15
15 [km]
Distance
Distance [km]
20
20
25
25
30
30
Figure
4. Currents
obtained
in simulations
the autotransformers
and SATS
for
Figure 4.
Currents
obtained
in simulations
of the of
autotransformers
ATS1,ATS1,
ATS2ATS2
and SATS
for different
Figure
4. Currents
obtained
in simulations
of
the autotransformers
ATS1,
ATS2
and SATS
for
different
fault
locations.
Fault
between
catenary
and
rail.
fault locations.
betweenFault
catenary
andcatenary
rail. and rail.
different Fault
fault locations.
between
7000
7000
IA1
IA1
6000
6000
IA2
IA2
Current[A]
[A]
Current
5000
5000
IA3
IA3
4000
4000
3000
3000
2000
2000
1000
1000
0
00
0
5
5
10
10
15
15 [km]
Distance
Distance [km]
20
20
25
25
30
30
Figure 5. Currents obtained in simulations of the autotransformers ATS1, ATS2 and SATS for different
fault locations. Fault between feeder and rail.
Energies 2017, 10, 340
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Figure 5. Currents obtained in simulations of the autotransformers ATS1, ATS2 and SATS for different
fault locations. Fault between feeder and rail.
Energies 2017, 10, 340
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As As
shown
in Figures
4 and
5, the
module
of the
current
in each
autotransformer
hashas
its highest
shown
in Figures
4 and
5, the
module
of the
current
in each
autotransformer
its highest
value
when
thethe
fault
occurs
alsoremarkable
remarkablethat
value
when
fault
occursvery
veryclose
closetotothe
thecorresponding
corresponding autotransformer.
autotransformer. ItIt isisalso
thatthe
thecurrent
currentofofone
oneautotransformer
autotransformerisisapproximately
approximately equal
equal to
to that
that of
of the
the adjacent
adjacentautotransformer
autotransformer at
at the
byby
these
two
autotransformers.
This
feature
is observed
when
themidpoint
midpointofofthe
thesection
sectiondelimited
delimited
these
two
autotransformers.
This
feature
is observed
when
thethe
fault
takes
place
between
thethe
catenary
andand
rail,rail,
andand
alsoalso
between
thethe
feeder
andand
rail.
fault
takes
place
between
catenary
between
feeder
rail.
4. New
Method
Ground
Fault
Location
25 Traction
kV Traction
Power
Systems
4. New
Method
for for
Ground
Fault
Location
in 2in×225×kV
Power
Systems
This
new
method
ground
fault
location
× kV
25 kV
power
systems
is divided
three
This
new
method
for for
ground
fault
location
in 2in×225
power
systems
is divided
intointo
three
different
stages
(Figure
different
stages
(Figure
6). 6).
Subsection A
Subsection B
Subsection C
MEASSUREMENT
Step 1
VC2
VC1
VC3
IA1
IA2
IA3
Fault
Traction Substation
ATS 1
ATS 2
SATS
SUBSECTION and CONDUCTOR
IDENTIFICATION
Step 2
IA3
IA2
Phase comparator.
IA1
90º
90º
180º
VC1
VC2
VC3
Previously calculated
short-circuit current vs distance.
Look-up Table.
Current [A]
FAULT LOCATOR
Step 3
IA3
IA2
Distance [km]
Fault Location
Figure
6. Simplified
layout
of the
location
method.
Figure
6. Simplified
layout
of the
location
method.
4.1.4.1.
Measurement
Measurement
In the
firstfirst
stage,
thethe
voltages
andand
thethe
currents
in the
different
autotransformers
should
be be
In the
stage,
voltages
currents
in the
different
autotransformers
should
measured,
as well
as the
phase
angle
between
them
(VC1(V
, IA1;, V
C2, IA2; VC3, IA3).
measured,
as well
as the
phase
angle
between
them
C1 IA1 ; VC2 , IA2 ; VC3 , IA3 ).
In the
case
of
a
ground
fault,
the
current
in
some
of
the
autotransformers
would
exceed
a
In the case of a ground fault, the current in some of the autotransformers
would
exceed
a prefixed
prefixed
threshold,
and
the location
be activated.
threshold,
and the
location
systemsystem
shouldshould
be activated.
Energies 2017, 10, 340
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4.2.
4.2. Subsection
Subsectionand
andConductor
ConductorIdentification
Identification
Afterwards,
Afterwards, the
the subsection
subsection between
between autotransformers
autotransformersand
and the
the positive
positive or
or negative
negative conductor
conductor
where
the
fault
has
occurred
are
identified
by
analysing
the
phase
angle
between
where the fault has occurred are identified by analysing the phase angle between the
the voltages
voltages and
and
currents
in
the
autotransformers,
as
was
summarised
in
Section
2.
The
completed
method
is
described
currents in the autotransformers, as was summarised in Section 2. The completed method is described
in
in [17].
[17].
4.3.
4.3. Fault
FaultLocator
Locator
Finally,
thefault
fault
locator
is based
on the previous
of in
thethecurrents
in the
Finally, the
locator
is based
on the previous
calculationcalculation
of the currents
autotransformer
autotransformer
foralong
a ground
alongof all
the positions
of a section,
per Section
3. The
for a ground fault
all the fault
positions
a section,
as per Section
3. The as
calculations
should
be
calculations
should be performed
taking
consideration
precise
data The
of the
power
performed specifically
taking intospecifically
consideration
the into
precise
data of thethe
power
system.
values
of
system.
The
values
of
the
fault
current
should
be
stored
as
look-up
tables.
the fault current should be stored as look-up tables.
The
The fault
fault location
location isis performed
performed by
by aa comparison
comparison of
of the
the current
current measured
measured in
in the
the two
two adjacent
adjacent
autotransformers
to
the
pre-calculated
value
storage
in
the
look-up
tables.
In
this
way,
the
location
autotransformers to
value storage in the look-up tables. In this way, the location of
of
fault
can
found.
flowchart
ground
fault
location
method
is presented
Figure
thethe
fault
can
bebe
found.
AA
flowchart
of of
thethe
ground
fault
location
method
is presented
in in
Figure
7. 7.
Start
Step 1
- GET VALUES OF CURRENTS IA1 , IA2 , IA3
AND VOLTAGES VA1 , VA2 , VA3
WHEN GROUND FAULTS HAPPENS
Step 2
- GET SUBSECTION WITH FAULT
- GET POSITIVE OR NEGATIVE CONDUCTOR
WITH FAULT
- COMPARE WITH CURRENT VALUES
IA1 (n), IA2 (n), IA3 (n) IN LOOK-UP TABLES
A
Subs = A
Yes
No
Subs = B
Step 3
No
IA1 (n) < IA1
yes
yes
n=n+1
No
E
A
Yes
IA2>IA1
No
IA1 (n) > IA1
Subs= C
No
No
E
Yes
IA3>IA2
No
IA2 (n) > IA2
Error
No
E
Yes
n=n+1
A
IA2 (n) < IA2
No
E
Yes
n=n+1
A
Yes
Yes
n=n+1
A
IA3 (n) < IA3
No
E
Yes
n=n+1
A
n=position
Figure7.7.Flowchart
Flowchartof
ofthe
theground
groundfault
faultlocation
locationmethod.
method.
Figure
This
method could
couldbebeeasily
easily
implemented
25power
kV power
systems,
as the voltages
and
This method
implemented
in 2in
× 225×kV
systems,
as the voltages
and currents
currents
in the autotransformers
recorded
byrelays
the installed
protection
relays
installed in and
the
in the autotransformers
are recorded are
by the
protection
in the
autotransformers,
autotransformers,
this sent
information
is normally
sent to
Supervisory
and Data
this information is and
normally
to the Supervisory
Control
andthe
Data
AcquisitionControl
System “SCADA”.
Acquisition System “SCADA”.
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4.4. Fault Location for Sections with n Subsections
4.4.Fault
FaultLocation
Location forSections
Sectionswith
withn nSubsections
Subsections
4.4.
This methodfor
is also valid
for any section that has at least two subsections, since the pattern that
follows
the
values
ofalso
the
modules
ofsection
the
currents
in at
such
cases
is
totally similar
tothe
that
in sections
This
method
valid
forany
any
section
thathas
has
atleast
least
two
subsections,
since
thepattern
pattern
that
This
method
isisalso
valid
for
that
two
subsections,
since
that
with
three
subsections.
follows
the
values
modules
of the
currents
in such
is totally
similar
in sections
follows
the
values
of of
thethe
modules
of the
currents
in such
casescases
is totally
similar
to thattointhat
sections
with
Figures
8
and
9
show
the
values
of
the
current
modulus
as
a
function
of
the
distance
to
the
fault
with
three
subsections.
three subsections.
in aFigures
section
two
subsections,
both
for
catenary
and
feeder
faults.
Figures8with
8and
and
9
show
the
values
of
the
current
modulus
as
a
function
of
the
distance
to
the
fault
9 show the values of the current modulus as a function of the distance to the fault
sectionwith
withtwo
twosubsections,
subsections,both
bothfor
forcatenary
catenaryand
andfeeder
feederfaults.
faults.
inina asection
Current
Current
[A] [A]
7000
7000
6000
IA1
6000
5000
IA2
IIA2
A1
5000
4000
4000
3000
3000
2000
2000
1000
1000
0
0
0
0
2
4
6
8
2
4
6
8
10
12
Distance [km]
10
12
Distance [km]
14
16
18
20
14
16
18
20
Figure 8. Currents in autotransformers as a function of the distance from the traction substation when
Figure 8. Currents in autotransformers as a function of the distance from the traction substation
aFigure
ground
fault occurs
between the catenary
and rail
along
different
in a section
withwhen
two
8. Currents
in autotransformers
as a function
of the
distance
fromzones
the traction
substation
when a ground fault occurs between the catenary and rail along different zones in a section with
subsections.
a ground fault occurs between the catenary and rail along different zones in a section with two
two subsections.
subsections.
7000
7000
6000
IA1
IA1
IA2
Current
Current
[A] [A]
6000
5000
IA2
5000
4000
4000
3000
3000
2000
2000
1000
1000
0
0
0
0
2
4
6
8
2
4
6
8
10
12
Distance [km]
10
12
Distance [km]
14
16
18
20
14
16
18
20
Figure 9. Currents in autotransformers as a function of the distance from the traction substation when a
Figure 9. Currents in autotransformers as a function of the distance from the traction substation when
ground fault occurs between the feeder and rail along different zones in a section with two subsections.
aFigure
ground
fault occurs
between the feeder
and railof along
different
zones
in a section
withwhen
two
9. Currents
in autotransformers
as a function
the distance
from
the traction
substation
subsections.
a ground fault occurs between the feeder and rail along different zones in a section with two
Furthermore
subsections. in Figures 10 and 11, the values of the current modulus are represented as a function
of the Furthermore
distance to theinground
fault
a section
with
four subsections
for both
catenary
feeder faults.
Figures
10 inand
11, the
values
of the current
modulus
are and
represented
as a
function
of the distance
to the 10
ground
fault
in values
a section
four subsections
catenary as
anda
Furthermore
in Figures
and 11,
the
of with
the current
modulus for
areboth
represented
feeder
faults.
function
of the distance to the ground fault in a section with four subsections for both catenary and
feeder faults.
Energies 2017, 10, 340
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2017,
10,10,
340340
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2017,
9 of 14
9 of
14 14
9 of
7000
7000
IA1
IA1
IA2
IA2
IA3
IA3
IA4
IA4
6000
6000
Current[A][A]
Current
5000
5000
4000
4000
3000
3000
2000
2000
1000
1000
0
00
0
5
5
10
10
15
20
25
15 Distance
20 [km] 25
Distance [km]
30
30
35
35
40
40
Figure10.10.Currents
Currentsininautotransformers
autotransformers asa afunction
functionofofthe
thedistance
distancefrom
fromthe
thetraction
tractionsubstation
substation
Figure
Figure 10. Currents
in autotransformersasas
a function
of the
distance from
the traction
substation
when
a
ground
fault
occurs
between
the
catenary
and
rail
along
different
zones
in
a
section
with
four
when
a ground
and rail
railalong
alongdifferent
differentzones
zonesinin
a section
with
when
a groundfault
faultoccurs
occursbetween
between the
the catenary
catenary and
a section
with
four
subsections.
four
subsections.
subsections.
7000
7000
IA1
IA1
IA2
IA2
IA3
IA3
IA4
IA4
6000
6000
Current[A][A]
Current
5000
5000
4000
4000
3000
3000
2000
2000
1000
1000
0
00
0
5
5
10
10
15
20
25
15 Distance
20 [km] 25
Distance [km]
30
30
35
35
40
40
Figure
11.11.
Currents
in autotransformers
as a function
of the of
distance
from thefrom
traction
when a
Figure
Currents
in autotransformers
as a function
the distance
the substation
traction substation
Figurefault
11. occurs
Currents
in autotransformers
as along
a function
of the
distance
from with
the traction
substation
ground
between
the
feeder
and
rail
different
zones
in
a
section
four
subsections.
when a ground fault occurs between the feeder and rail along different zones in a section with four
when a ground fault occurs between the feeder and rail along different zones in a section with four
subsections.
subsections.
From all the results illustrated in previous figures it can be concluded that this ground fault
From
all the
results illustrated
in previous
figures
it can
be concluded that this ground fault
location
process
is applicable
to any section
with two
or more
subsections.
From all the results illustrated in previous figures it can be concluded that this ground fault
location process is applicable to any section with two or more subsections.
process
is applicable to any section with two or more subsections.
5. location
Experimental
Tests
5. Experimental
In addition toTests
the computer simulations, numerous tests have been performed in the laboratory
5. Experimental
Tests
to obtain
the
necessary
in order
to store in
memory tests
the currents
of the
autotransformers
used into
In addition to thetables
computer
simulations,
numerous
have been
performed
in the laboratory
In addition to the computer simulations, numerous tests have been performed in the laboratory to
the
circuit
represented
in
Figure
12
when
several
ground
faults
are
performed.
obtain the necessary tables in order to store in memory the currents of the autotransformers used in the
obtain the necessary tables in order to store in memory the currents of the autotransformers used in the
Therepresented
experimental
setup used
in the
laboratory
is faults
shown
inperformed.
Figure 13. It simulates the circuit of
circuit
in Figure
12 when
several
ground
are
circuit represented in Figure 12 when several ground faults are performed.
Figure 12. In this experimental setup, the traction substation was implemented using a power source
(1) and the traction transformer was made using two transformers (2) and (3) providing 25 V AC each
(see Figure 13).
Energies 2017, 10, 340
10 of 14
Subsection A
Subsection B
Subsection C
Energies 2017, 10, 340
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10 of 14
10 of 14
Subsection A
VC1
Subsection B
L2
L1
IA2
VC1
VC3
L
L
IA1
L
IA3
VC2
L2
Fault
VC3
L
IA1
L1
Subsection C
L
Fault
TSTraction Substation
VC2
ATS 1
IA2
L
ATS 2
IA3
L
SATS
Figure 12. Laboratory circuit to simulate a section fed by a 2 × 25 kV system with two conductors and
ground return. A fault between the catenary and rail in subsection A is represented.
TSTraction Substation
L
ATS 1
L
ATS 2
L
SATS
The experimental setup used in the laboratory is shown in Figure 13. It simulates the circuit of
Figure 12. Laboratory circuit to simulate a section fed by a 2 × 25 kV system with two conductors and
Figure
circuit tosetup,
simulate
section fed
by a 2 ×was
25 kV
system with using
two conductors
and
Figure
12.12.
In Laboratory
this experimental
the atraction
substation
implemented
a power source
ground return. A fault between the catenary and rail in subsection A is represented.
A transformer
fault betweenwas
the made
catenary
andtwo
rail transformers
in subsection A
represented.
(1)ground
and thereturn.
traction
using
(2)isand
(3) providing 25 V AC each
(see Figure 13).
The experimental setup used in the laboratory is shown in Figure 13. It simulates the circuit of
Figure 12. In this experimental setup, the traction substation was implemented using a power source
(1) and the traction transformer was made using two transformers (2) and (3) providing 25 V AC each
(see Figure 13).
Figure 13. Laboratory setup for 2 × 25 kV power system fault location testing.
Figure 13. Laboratory setup for 2 × 25 kV power system fault location testing.
The section is divided into three subsections by autotransformers ATS1, ATS2 and SATS (4). The
The section
is divided
into
three subsections
by autotransformers
ATS1, ATS2
and SATS
distributed
impedances
of the
catenary
and feeder were
simulated using inductive
impedances
L (5).(4).
Figure
13.
Laboratory
setup
for
2
×
25
kV
power
system
fault
location
testing.
The
distributed
ofwas
the considered
catenary and
feeder and
werenosimulated
using
inductiveToimpedances
Moreover,
the impedances
rail impedance
negligible
impedance
was installed.
simulate
L (5).
Moreover,
the
rail
impedance
was
considered
negligible
and
no
impedance
was
installed.
faults (7) along different points of each subsection, variable inductors L1 and L2 (6), were used.
Such
The section is divided into three subsections by autotransformers ATS1, ATS2 and SATS (4). The
To inductors
simulate faults
(7)
along
different
points
of
each
subsection,
variable
inductors
L1
and
L2
(6), were
can be observed in detail in Figure 14.
distributed impedances of the catenary and feeder were simulated using inductive impedances L (5).
used. Such
inductors
can
be observedsetup
in detail
in Figure
The values
of the
experimental
impedances
per14.
unit length of the catenary, feeder and rail
Moreover, the rail impedance was considered negligible and no impedance was installed. To simulate
values
of the3.experimental
setup impedances
per
unitinlength
of the catenary, feeder and rail
areThe
shown
in Table
No mutual impedances
have been
taken
consideration
faults (7) along different points of each subsection, variable inductors L1 and L2 (6), were used. Such
are shown
in
Table
3.
No
mutual
impedances
have
been
taken
in
consideration
inductors can be observed in detail in Figure 14.
Table 3. Experimental setup impedance values of railway conductors.
The values of the experimental setup impedances per unit length of the catenary, feeder and rail
Table 3. Experimental setup impedance values of railway conductors.
are shown in Table 3. No mutual
impedancesSelf-Impedance
have been takenΩ/km
in consideration
Conductor
Catenary
Z
C
0.10
+
j1.00
Conductor
Self-Impedance Ω/km
Table 3. Experimental
Feeder setup
ZF impedance
0.10 +values
j1.00 of railway conductors.
Catenary
ZC
0.10 + j1.00
Rail
ZR
0
Conductor
Self-Impedance
Ω/km
Feeder
ZF
Rail
Catenary ZZ
RC
0.10 + j1.00
0
0.10 + j1.00
Feeder
ZF
0.10 + j1.00
Railtransformer
ZR
0
Additional information about the
and autotransformers
used in the experimental
setup is shown in Table 4.
Energies 2017, 10, 340
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11 of 14
Additional information about the transformer and autotransformers used in the experimental
2017, 10, 340
11 of 14
setupEnergies
is shown
in Table 4.
Table 4. Experimental setup transformers and autotransformers ratings.
Additional information about the transformer and autotransformers used in the experimental
Table 4. Experimental setup transformers and autotransformers ratings.
setup is shown in Table 4.
Main Transformer
Main Transformer
Voltage ratio
400/2 × 25 kV
V
Voltage
ratio
400/2
× 25 kV VA Vratings.
Table 4. Experimental
setup transformers
and autotransformers
Rated
power
1600
Rated power
Short-circuit
voltage
5.38 1600
% VA
Main Transformer
Short-circuit voltage
5.38
%
Autotransformers400/2 × 25 kV
Voltage ratio
V
Autotransformers
Rated
power
VA
Voltage
ratio
50/25 1600
V
Voltage ratiovoltage
50/25
V
Short-circuit
5.38
Rated
power
300
VA %
Rated power
300
VA
Short-circuit voltageAutotransformers
2.17
%
Short-circuit
voltage
2.17
%V
Voltage ratio
50/25
Rated power
300
VA
With this
this setup,
setup,the
thecurrents
currents
IA1
, and
measured.
These
currents
were
flowing
in
A3 were
With
IA1
, I,A2IA2
, and
IA3Iwere
measured.
currents
flowing
in the
% were
Short-circuit
voltage
2.17These
the three
autotransformers
a fault
was executed
between
the catenary
andThese
rail. faults
These
three
autotransformers
usedused
whenwhen
a fault
was executed
between
the catenary
and rail.
faults
were
made
along
the
section
that
simulated
a
length
of
30
km
with
three
subsections
of
10
km,
With
this
setup,
the
currents
I
A1
,
I
A2
,
and
I
A3
were
measured.
These
currents
were
flowing
in
the
were made along the section that simulated a length of 30 km with three subsections of 10 km,
performing
measurements used
everywhen
0.5 km.
km.
Figure
15
shows the
the evolution
evolution
of these
theseand
currents
depending
three autotransformers
a fault
was15
executed
between
the catenary
rail. These
faults
performing
measurements
every
0.5
Figure
shows
of
currents
depending
were
made
along
the
section
that
simulated
a
length
of
30
km
with
three
subsections
of
10
km,
on
the
position
where
the
fault
was
developed
for
a
catenary-ground
fault.
on the position where the fault was developed for a catenary-ground fault.
performing measurements every 0.5 km. Figure 15 shows the evolution of these currents depending
on the position where the fault was developed for a catenary-ground
fault.
Variable
inductance 10 x 0.5 Ω
(a)
(b)
(a)
(b)
Figure 14. Variable inductance (L1, L2) used to simulate faults at any point of any subsection; (a)
Figure 14. Variable inductance (L1, L2) used to simulate faults at any point of any subsection; (a) Picture;
Figure
14. Variable
inductance (L1, L2) used to simulate faults at any point of any subsection; (a)
Picture;
(b) Electrical
(b) Electrical
diagram.diagram.
Picture; (b) Electrical diagram.
1200
1200
I
A1
IA1
1000
1000
Current [mA]
Current [mA]
800
600
400
IA2
IA2
800
I
A3
IA3
600
400
200 200
0
0
0
0
10 10
20 20
30 30
Distance
[km]
Distance
[km]
4040
50
50
60
60
Figure
15. Autotransformers
current
distribution
tests
witha afault
faultbetween
betweenthe
thecatenary
catenary and rail.
Figure
15. Autotransformers
current
distribution
in in
thethe
tests
with
rail.
Figure 15. Autotransformers current distribution in the tests with a fault between the catenary and rail.
Energies 2017, 10, 340
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12 of 14
12 of 14
Also
facility,
thethe
currents
flowing
in the
three
autotransformers
(IA1(I, A1
IA2
and
IA3IA3
) were
Alsoininthis
this
facility,
currents
flowing
in the
three
autotransformers
, IA2
and
) were
measured
when
a
fault
was
made
between
the
feeder
and
rail
every
0.5
km
along
the
section.
The
results
measured when a fault was made between the feeder and rail every 0.5 km along the section. The
are
shown
inshown
Figurein
16.Figure 16.
results
are
1200
IA1
1000
IA2
Current [mA]
800
IA3
600
400
200
0
0
5
10
15
Distance [km]
20
25
30
Figure
16.
feeder and
and rail.
rail.
Figure
16.Autotransformers
Autotransformerscurrent
currentdistribution
distributionin
inthe
thetests
tests with
with aa fault
fault between the feeder
observed,inincase
caseofofground
groundfault,
fault,the
thecurrent
currentdistributions
distributionsobtained
obtainedthrough
throughexperimental
experimental
AsAs
it it
is isobserved,
results
(Figures
15
and
16)
are
similar
to
those
obtained
through
computer
simulations
(Figures
4 and
results (Figures 15 and 16) are similar to those obtained through computer simulations (Figures 4 and
5).
5).
Therefore
the
simulation
model
is
validated,
as
well
as
the
location
method.
Therefore the simulation model is validated, as well as the location method.
Conclusions
6.6.Conclusions
We
have
described
a new
method
ground
fault
location
2 ×2525kV
kVtraction
tractionpower
powersystems
systems
We
have
described
a new
method
of of
ground
fault
location
forfor
2×
based
the
measurement
the
currents
and
voltages
the
autotransformers
along
a section.
based
onon
the
measurement
ofof
the
currents
and
voltages
inin
the
autotransformers
along
a section.
Thesubsection
subsectionand
andthe
thepositive
positiveorornegative
negativeconductors
conductorswhere
wherethe
theground
groundfault
faulttakes
takesplace
placeare
are
The
determined
by analyzing
the angle
phasebetween
angle the
between
and
theautotransformers
currents in the
determined
by analyzing
the phase
voltagesthe
andvoltages
the currents
in the
at both ends of the subsection.
atautotransformers
both ends of the subsection.
Thefault
fault
locationis isperformed
performedbyby
a control
device,
which
the
values
the
autotransformers
The
location
a control
device,
inin
which
the
values
ofof
the
autotransformers
currents,
the
case
groundfault
faultalong
alongthe
thesection,
section,have
havebeen
beenpreviously
previouslyrecorded
recorded
memory
currents,
inin
the
case
ofofa aground
ininitsitsmemory
as
look-up
tables.
This
control
device
receives
the
readings
from
the
autotransformers
protection
as look-up tables. This control device receives the readings from the autotransformers protection relays.
By comparing
the measured
in the autotransformers
to therecorded
previously
recorded
Byrelays.
comparing
the measured
currents incurrents
the autotransformers
to the previously
values,
the
values,
the fault
position
can be determined.
fault
position
can be
determined.
Thismethod
methodis isalso
alsoeconomical,
economical,asasthe
thevoltage
voltageand
andcurrent
currentmeasurement
measurementtransformers
transformersand
and
This
protection
relays
are
already
installed
the
autotransformer
substations.The
The
new
location
method
protection
relays
are
already
installed
inin
the
autotransformer
substations.
new
location
method
could
implemented
in the
Supervisory
Control
Acquisition
System
“SCADA”
× 25
could
bebe
implemented
in the
Supervisory
Control
andand
DataData
Acquisition
System
“SCADA”
of 2 ×of252 kV
kV
power
systems,
in
which
the
information
from
autotransformer
protection
relays
is
normally
power systems, in which the information from autotransformer protection relays is normally available.
available.
method
hasbybeen
testedsimulations
by computer
simulations
and
experimental
tests,
This
methodThis
has been
tested
computer
and
experimental
laboratory
tests, laboratory
both obtaining
both
obtaining
suitable
results.
suitable results.
Author
and included
includedthe
themathematical
mathematicalformulation
formulationofof
AuthorContributions:
Contributions:Jesús
JesúsSerrano
Serrano developed
developed the study and
the
the
tractionpower
powersystems
systemsininthe
the simulated
simulated models.
models. Carlos
Carlos A.
A. Platero
traction
Platero and
and Ricardo
RicardoGranizo
Granizoperformed
performedthe
the
laboratory tests and checked the validity of the new method. Máximo López-Toledo revised and improved the
laboratory tests and checked the validity of the new method. Máximo López-Toledo revised and improved the
MATLAB model. All the authors contributed to writing this article, including their conceptual approaches to the
MATLAB
model. All the authors contributed to writing this article, including their conceptual approaches to the
solution
obtained.
solution obtained.
Conflicts of Interest: The authors declare no conflict of interest.
Conflicts of Interest: The authors declare no conflict of interest.
Abbreviations
Energies 2017, 10, 340
13 of 14
Abbreviations
The following abbreviations are used in this manuscript:
AC
AT
ATS
IA1
IA2
IA3
I
IAi
L
L1
L2
SATS
V1
V2
VCi
ZC
ZF
ZR
ZCF
ZCR
ZFR
Alternating current.
Auto-transformer.
Auto-transformer station.
Catenary current in autotransformer 1.
Catenary current in autotransformer 2.
Catenary current in autotransformer 3.
Autotransformer number: 1, 2, 3, . . . N.
Current input from catenary in autotransformer “i”.
Inductive impedance.
Adjustable Inductive impedance 1.
Adjustable Inductive impedance 2.
Autotransformer station at the end of the section.
Voltage source 1.
Voltage source 2.
Catenary voltage in autotransformer “i”.
Catenary self-impedance value per unit length.
Feeder self-impedance value per unit length.
Rail self-impedance value per unit length.
Mutual impedance Catenary-Feeder value per unit length.
Mutual impedance Catenary-Rail value per unit length.
Mutual impedance Feeder-Rail value per unit length.
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