Method and device for fault location on three terminal power line
View Patent ↗A method for locating a fault in three terminal power line, having sections located in front of or behind of the tap point and which assumes occurrence of the fault in at least one of those sections. Three phase currents and voltages are measured at one end of the power lines system. The amplitudes of load currents in the remaining sections of the power lines system are measured before a fault occurs. The measurements of the amplitudes of load currents are stored in the remaining sections of the power lines system. Impedance data of the network are determined. The symmetrical components approach is used when calculating the location of the fault.
1. A method for locating a fault in a network including a three terminal power line, having three line sections located in front of or behind a tap point and a fault locating unit arranged at a first of the three terminals in a first of the three sections, wherein the fault occurs in at least one of the three sections, the method comprising:
measuring three phase currents and voltages at the first terminal in the first section;
measuring, before the fault occurs, amplitudes of load currents in a second section and a third section of the three sections;
storing the measured amplitudes of load currents in the fault locating unit;
calculating pre-fault phasors of currents in the second section and the third section from the measured amplitudes of load currents;
determining impedance data of the network; and
determining a location of the fault by determining a distance to the fault based upon the measured three phase currents and voltages, the pre-fault phasors of currents and the impedance data of the network using a symmetrical components approach.
2. The method according to claim 1 , further comprising:
using subroutines (Sub_A, Sub_B and Sub_C) for calculating the fault location.
3. The method according to claim 1 , further comprising:
using a subroutine (Sub_A) for resolving d FA —the distance to fault, counted from the bus A, and RFA—the fault resistance.
4. The method according to claim 1 , further comprising:
using the equation:
A
_
2
d
FA
2
+
A
_
1
d
FA
+
A
_
0
+
A
_
00
R
FA
=
0
where
:
A
_
2
=
Z
_
1
LA
K
_
A
1
A
_
1
=
Z
_
1
LA
L
_
A
1
-
Z
_
Ap
K
_
A
1
A
_
0
=
-
Z
_
Ap
L
_
A
1
A
_
00
=
M
_
A
1
(
α
_
F
1
Δ
I
_
A
1
+
α
_
F
2
I
_
A
2
)
I
_
Ap
Z
_
Ap
=
V
_
Ap
I
_
Ap
-
apparent
impedance
of
the
fault
loop
.
(
5
)
5. The method according to claim 1 , further comprising:
using a subroutine (Sub_B) for identifying faults in a another section (BT).
6. The method according to claim 1 , further comprising:
using the equation:
V
_
Tp
-
(
1
-
d
FB
)
Z
_
1
LB
I
_
TBp
-
R
FB
(
α
_
F
1
Δ
I
_
TB
1
k
_
FB
1
+
α
_
F
2
I
_
TB
2
k
_
FB
2
)
=
0
(
6
)
where:
Fault loop voltage transferred to the tap point T:
V Tp = a 1 V T1 + a 2 V T2 + a 0 V T0 (7)
fault loop current transferred to the tap point T (from the side of the section BT— FIG. 1 ):
I
_
TBp
=
α
_
1
(
Δ
I
_
TB
1
+
I
_
TB
1
pre
)
+
α
_
2
I
_
TB
2
+
α
_
0
Z
_
0
LB
Z
_
1
LB
I
_
TB
0
(
8
)
a 1 , a 2 , a 0 —weighting coefficients (Table I)),
k FB1 , k FB2 —fault current distribution factors for the positive,
negative sequences, respectively,
a F1 , a F2 , a F0 —share coefficients (Table II).
transfer of the fault loop voltage from the bus A to the tap point T can be accomplished as follows:
[
V
_
T
1
V
_
T
2
V
_
T
0
]
=
[
V
_
A
1
V
_
A
2
V
_
A
0
]
-
[
Z
_
1
LA
I
_
A
1
Z
_
1
LA
I
_
A
2
Z
_
0
LA
I
_
A
0
]
.
(
9
)
7. The method according to claim 1 , further comprising:
using a set of equations (14-17) for solving unknowns: real( I TB1 pre ), imag( I TB1 pre ), real( I TC1 pre ), imag( I TC1 pre ), when solving gives the required pre-fault phasors of currents from the remote terminals (B,C).
8. The method according to claim 1 , further comprising:
substituting the fault current distribution factors (18) into a general fault model (6) resulting in a quadratic formula for complex numbers, analogously as for the case of faults occurring in the section AT (5).
9. The method according to claim 1 , further comprising:
selecting the valid subroutine, by indicating which subroutine yields the results corresponding to the real distance to fault and fault resistance.
10. A device for locating a fault in a network including a three terminal power lines system, having three line sections located in front of or behind a tap point and a fault locating unit arranged at a first of the three terminals in a first of the three sections, wherein the fault occurs in at least one of the three sections, the device comprising:
means for measuring current and voltages at the first terminal in the first section;
means for measuring, before a fault occurs, amplitudes of load currents in a second section and a third section of the three sections;
storage means configured to store the measured amplitudes of load currents in the fault locating unit;
means for calculating pre-fault phasors of currents in the second section and the third section from the measured amplitudes of load currents;
means for determining impedance data of the network; and
means for determining a location of the fault by determining a distance to the fault based upon the measured three phase currents and voltages, the pre-fault phasors of currents and the impedance data of the network using a symmetrical components approach.
11. The device according to claim 10 , further comprising:
means for using subroutines (Sub_A, Sub_B and Sub_C) for calculating the fault location.
12. The device according to claim 10 , further comprising:
means for execute a subroutine (Sub_A) for resolving d FA —the distance to fault, counted from the bus A, and RFA—the fault resistance.
13. The device according to claim 10 , further comprising:
means for calculating:
A
_
2
d
FA
2
+
A
_
1
d
FA
+
A
_
0
+
A
_
00
R
FA
=
0
where
:
A
_
2
=
Z
_
1
LA
K
_
A
1
A
_
1
=
Z
_
1
LA
L
_
A
1
-
Z
_
Ap
K
_
A
1
A
_
0
=
-
Z
_
Ap
L
_
A
1
A
_
00
=
M
_
A
1
(
α
_
F
1
Δ
I
_
A
1
+
α
_
F
2
I
_
A
2
)
I
_
Ap
Z
_
Ap
=
V
_
Ap
I
_
Ap
-
apparent
impedance
of
the
fault
loop
.
(
5
)
14. The device according to claim 10 , further comprising:
means for execute a subroutine (Sub_B) for identifying faults in a another section (BT).
15. The device according to claim 10 , further comprising:
means for executing the equation:
V
_
Tp
-
(
1
-
d
FB
)
Z
_
1
LB
I
_
TBp
-
R
FB
(
α
_
F
1
Δ
I
_
TB
1
k
_
FB
1
+
α
_
F
2
I
_
TB
2
k
_
FB
2
)
=
0
(
6
)
where:
Fault loop voltage transferred to the tap point T:
V Tp = a 1 V T1 + a 2 V T2 + a 0 V T0 (7)
Fault loop current transferred to the tap point T (from the side of the section BT— FIG. 1 ):
I
_
TBp
=
α
_
1
(
Δ
I
_
TB
1
+
I
_
TB
1
pre
)
+
α
_
2
I
_
TB
2
+
α
_
0
Z
_
0
LB
Z
_
1
LB
I
_
TB
0
(
8
)
a 1 , a 2 , a 0 —weighting coefficients (Table I)),
k FB1 , k FB2 —fault current distribution factors for the positive,
negative sequences, respectively,
a F1 , a F2 , a F0 —share coefficients (Table II).
Transfer of the fault loop voltage from the bus A to the tap point T can be accomplished as follows:
[
V
_
T
1
V
_
T
2
V
_
T
0
]
=
[
V
_
A
1
V
_
A
2
V
_
A
0
]
-
[
Z
_
1
LA
I
_
A
1
Z
_
1
LA
I
_
A
2
Z
_
0
LA
I
_
A
0
]
.
(
9
)
16. The device according to claim 10 , further comprising:
means for using a set of equations (14-17) for solving unknowns: real( I TB1 pre ), imag( I TB1 pre ), real( I TC1 pre ), imag( I TC1 pre ), when solving gives the required pre-fault phasors of currents from the remote terminals (B,C).
17. The device according to claim 10 , further comprising:
means for substituting the fault current distribution factors (18) into a general fault model (6) resulting in a quadratic formula for complex numbers, analogously as for the case of faults occurring in the section AT (5).
18. The device according to claim 10 , further comprising:
means for selecting the valid subroutine, by indicating which subroutine yields the results corresponding to the real distance to fault and fault resistance.
19. A computer program product, comprising:
a computer readable medium; and
computer program instructions recorded on the computer readable medium and executable by a processor for performing the steps of a method for locating a fault in a network including a three terminal power line, having three line sections located in front of or behind a tap point and a fault locating unit arranged at a first of the three terminals in a first of the three sections, wherein the fault occurs in at least one of the three sections, the method comprising:
measuring three phase currents and voltages at the first terminal in the first section;
measuring, before the fault occurs, amplitudes of load currents in a second section and a third section of the three sections;
storing the measured amplitudes of load currents in the fault locating unit;
calculating pre-fault phasors of currents in the second section and the third section from the measured amplitudes of load currents;
determining impedance data of the network; and
determining a location of the fault by determining a distance to the fault based upon the measured three phase currents and voltages, the pre-fault phasors of currents and the impedance data of the network using a symmetrical components approach.
20. The computer program product according to claim 19 , wherein the computer program instructions are further for performing the step of
at least partially providing the computer program instructions through a network.
21. The computer program product according to claim 20 , wherein the network is the internet.