ABB RELION RET670, Applications Manual

Page: 314 / 1016

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
177 can be used to calculate the reach in reverse direction when the
zone is used for blocking scheme, weak-end infeed and so on.
( )
1.2 2
³ × -
Zrev ZL Z rem
EQUATION1525 V5 EN-US
(Equation 177)
Where:
ZL
is the protected line impedance
Z2rem is zone2 setting at remote end of protected line
In some 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.
8.5.3.5 Setting of zones for parallel line application
SEMOD154704-48 v1
Parallel line in service – Setting of zone1
SEMOD154704-50 v1
With reference to section "Parallel line applications" , the zone reach can be set to 85%
of protected line.
Parallel line in service – setting of zone2
SEMOD154704-53 v2
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
142 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 178)
X
0E
X
0
X
m0
+ =
EQUATION554 V1 EN-US
(Equation 179)
Section 8
1MRK 504 163-UUS A
Impedance protection
308 Transformer protection RET670 2.2 ANSI
Application manual