ABB RELION RET670, Applications Manual

Page: 346 / 1016

rem L
1.2 Z2 Z
-
rev
Z
³ ×
EQUATION2314 V1 EN-US
(Equation 222)
Where:
Z
L
is the protected line impedance
Z2
rem
is zone 2 setting at remote end of protected line.
In many applications it might be necessary to consider the enlarging factor due to fault
current infeed from adjacent lines in the reverse direction in order to obtain certain
sensitivity.
8.9.3.5 Setting of zones for parallel line application
SEMOD55087-50 v2
Parallel line in service – Setting of zone 1
GUID-F10BF2FF-7B0F-40B0-877B-081E1D5B067B v1
With reference to section "Parallel line applications" , the zone reach can be set to 85%
of protected line.
However, influence of mutual impedance has to be taken into account.
Parallel line in service – setting of zone 2
GUID-8EAD617A-D33B-453C-83FC-21E3CFC37CB1 v1
Overreaching zones (in general, zones 2 and 3) must overreach the protected circuit in
all cases. The greatest reduction of a reach occurs in cases when both parallel circuits
are in service with a single phase-to-ground fault located at the end of a protected line.
The equivalent zero sequence impedance circuit for this case is equal to the one in
figure
126 in section "Parallel line applications" .
The components of the zero sequence impedance for the overreaching zones must be
equal to at least:
R
0E
R
0
R
m0
+ =
EQUATION553 V1 EN-US
(Equation 223)
X
0E
X
0
X
m0
+ =
EQUATION554 V1 EN-US
(Equation 224)
Check the reduction of a reach for the overreaching zones due to the effect of the zero
sequence mutual coupling. The reach is reduced for a factor:
Section 8
1MRK 504 163-UUS A
Impedance protection
340 Transformer protection RET670 2.2 ANSI
Application manual