Z
V
I
Z
I
I
I
Z
I
I
I
I
R
Z
I
I
Z
AF
A
A
AC
A
C
A
CF
A
C
B
A
F
AC
C
A
C
=
=
+
+
⋅
+
+
+
⋅
=
+
+
⋅
1
F
F
C
B
A
F
I
I
I
R
+
+
+
⋅
1
EQUATION302 V5 EN-US
(Equation 349)
A
B
21
C
I A
IB
Z AC
Z CB
Z CF
IA+ IB
ANSI05000457-2-en.vsd
F
ANSI05000457 V2 EN-US
Figure 222:
Setting of overreaching zone
8.13.4.4
Setting of reverse zone
GUID-C08EC148-B90C-4A20-8993-707E63545946 v2
The reverse zone (zone RV) 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. The equation can be used to calculate the reach in reverse direction when the
zone is used for blocking scheme, weak-end infeed, and so on.
Z
rev
1.2 × (Z2
rem
- ZL)
>
_
GUID-ABFB1C53-F12A-45D5-90CC-907C9FA0EFC3 V1 EN-US
(Equation 350)
Where:
ZL
is the protected line impedance.
Z2rem is the zone 2 setting (zone used in the POTT scheme) at the remote end of the protected line.
In many applications it might be necessary to consider the enlarging factor due to the
fault current infeed from adjacent lines in the reverse direction in order to obtain
certain sensitivity.
8.13.4.5
Series compensated and adjacent lines
GUID-33C23BA9-5807-4E9E-859A-12D6A76304C0 v1
1MRK 504 163-UUS A
Section 8
Impedance protection
Transformer protection RET670 2.2 ANSI
435
Application manual
Summary of Contents for RELION RET670
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