GE c60 Instruction Manual page 450
Breaker protection system
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FAULT LOCATOR
m = sought pu distance to fault
Z = positive sequence impedance of the line
The currents from the local and remote systems can be parted between their fault (F) and pre-fault load (pre) components:
and neglecting shunt parameters of the line:
Inserting the I
and I
A
Assuming the fault components of the currents, I
impedance, does not have any imaginary part gives:
where Im() represents the imaginary part of a complex number. Solving this equation for the unknown m creates the
following fault location algorithm:
where * denotes the complex conjugate and
Depending on the fault type, appropriate voltage and current signals are selected from the phase quantities before
applying the preceding two equations (the superscripts denote phases, the subscripts denote stations).
For AG faults:
For BG faults:
For CG faults:
For AB and ABG faults:
For BC and BCG faults:
8
For CA and CAG faults:
where K
is the zero sequence compensation factor (for the first six equations).
0
For ABC faults, all three AB, BC, and CA loops are analyzed and the final result is selected based upon consistency of the
results.
The element calculates the distance to the fault (with m in miles or kilometers) and the phases involved in the fault.
8-2
equations into the V
equation and solving for the fault resistance yields:
B
A
R
AF
Im
m
I
=
AF
V
=
V
A
V
=
V
A
V
=
V
A
V
=
V
A
V
=
V
A
V
=
V
A
I
=
I
+
I
A
AF
Apre
I
=
I
I
–
B
BF
Apre
V
m Z I
–
A
A
=
------------------------------ -
F
I
BF
I
1
+
----- -
AF
I
AF
and I
are in phase, and observing that the fault resistance, as
BF
V
m Z I
–
A
A
------------------------------ -
=
0
I
AF
Im V
I
A
AF
=
---------------------------------- -
Im Z I
I
A
AF
.
I
I
–
A
Apre
A
A
,
I
=
I
+
K
I
A
A
A
0
0A
B
B
,
I
=
I
+
K
I
A
A
A
0
0A
C
BC
,
I
=
I
+
K
I
A
A
A
0
0A
A
B
A
B
V
,
I
=
I
I
–
–
A
A
A
A
A
B
C
B
C
V
,
I
=
I
I
–
–
A
A
A
A
A
C
A
C
A
V
,
I
=
I
I
–
–
A
A
A
A
A
C60 BREAKER PROTECTION SYSTEM – INSTRUCTION MANUAL
CHAPTER 8: THEORY OF OPERATION
Eq. 8-2
Eq. 8-3
Eq. 8-4
Eq. 8-5
Eq. 8-6
Eq. 8-7
Eq. 8-8
Eq. 8-9
Eq. 8-10
Eq. 8-11
Eq. 8-12
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