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1MRK 506 369-UEN B
8.1.3.4
Line distance protection REL670 2.2 IEC
Application manual
avoid unwanted operation in cases when the telecommunication for the short
adjacent line at remote end is down during faults. The zone2 must not be reduced
below 120% of the protected line section. The whole line must be covered under all
conditions.
The requirement that the zone 2 shall not reach more than 80% of the shortest
adjacent line at remote end is highlighted with a simple example below.
If a fault occurs at point F (as shown in figure 100, also for the explanation of all
abbreviations used), the IED at point A senses the impedance:
+
+
+
V
I
I
I
I
I
A
A
C
A
C
B
=
=
+
⋅
+
Z
Z
Z
AF
AC
CF
I
I
I
A
A
A
EQUATION302 V5 EN-US
A
I A
Z<
IEC05000457 V2 EN-US
Figure 100:
Setting of overreaching zone
Setting of reverse zone
The reverse zone is applicable for purposes of scheme communication logic,
current reversal logic, weak-end-infeed logic, and so on. The same applies to the
back-up protection of the bus bar or power transformers. It is necessary to secure,
that it always covers the overreaching zone, used at the remote line IED for the
telecommunication purposes.
Consider the possible enlarging factor that might exist due to fault infeed from
adjacent lines. Equation
when the zone is used for blocking scheme, weak-end infeed and so on.
(
³
×
-
Zrev
1.2
ZL
Z rem
2
EQUATION1525 V5 EN-US
Where:
ZL
is the protected line impedance
Z2rem
is zone2 setting at remote end of protected line.
+
I
I
I
C
C
B
⋅
=
+
1
+
⋅
+
1
+
⋅
R
Z
Z
R
AC
C
F F
F
F
I
I
A
A
Z AC
Z CB
C
Z CF
I A+ I C
I C
74
can be used to calculate the reach in reverse direction
)
Section 8
Impedance protection
F
B
I B
IEC05000457-2-en.vsd
(Equation 73)
SEMOD168247-33 v2
(Equation 74)
191
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