The reach of the distance protection zone 1 will be different depending on the operation
condition of the parallel line. This can be handled by the use of different setting groups for
handling the cases when the parallel line is in operation and out of service and earthed at both
ends.
The distance protection within the IED can compensate for the influence of a zero sequence
mutual coupling on the measurement at single phase-to-earth faults in the following ways, by
using:
•
The possibility of different setting values that influence the earth-return compensation
for different distance zones within the same group of setting parameters.
•
Different groups of setting parameters for different operating conditions of a protected
multi circuit line.
Most multi circuit lines have two parallel operating circuits.
Parallel line applications
GUID-9980E92C-EDB1-4E0C-A4BD-167C896199A1 v1
This type of networks are defined as those networks where the parallel transmission lines
terminate at common nodes at both ends.
The three most common operation modes are:
1.
parallel line in service.
2.
parallel line out of service and earthed.
3.
parallel line out of service and not earthed.
Parallel line in service
GUID-F792E7FD-2265-4250-9026-1F03039FB0B5 v1
This type of application is very common and applies to all normal sub-transmission and
transmission networks.
Let us analyze what happens when a fault occurs on the parallel line see figure
From symmetrical components, we can derive the impedance Z at the relay point for normal
lines without mutual coupling according to equation
.
ph
ph
0
1
ph
0
N
ph
0
1
U
U
Z
Z
I
3I K
I
3I
3 Z
Z
=
=
-
+
×
+
×
×
EQUATION2311 V1 EN-US
(Equation 259)
ph
ph
0
1
ph
N
ph
0
1
0
V
V
Z
Z
I
3
K
I
3I
3 Z
I
Z
=
=
-
+
×
+
×
×
EQUATION1275 V3 EN-US
(Equation 259)
Where:
U
ph
is phase to earth voltage at the relay point
I
ph
is phase current in the faulty phase
3I
0
is earth fault current
Z
1
is positive sequence impedance
Z
0
is zero sequence impedance
1MRK 505 343-UEN B
Section 7
Impedance protection
273
Application manual
Содержание Relion 670 series
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