ABB REL670 2.2 IEC, Applications Manual

Page: 234 / 908

Consider the possible enlarging factor that might exist due to fault infeed from
adjacent lines. Equation
128 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 128)
Where:
ZL
is the protected line impedance
Z2rem 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.
8.3.3.5 Setting of zones for parallel line application
SEMOD55087-50 v2
Parallel line in service – Setting of zone 1
SEMOD55087-52 v3
With reference to section "Parallel line applications" , the zone reach can be set to
85% of the protected line.
However, influence of mutual impedance has to be taken into account.
Parallel line in service – setting of zone 2
SEMOD55087-55 v4
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-earth 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
113 in section "Parallel line in service" .
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 129)
X
0E
X
0
X
m0
+ =
EQUATION554 V1 EN-US
(Equation 130)
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 506 369-UEN B
Impedance protection
228 Line distance protection REL670 2.2 IEC
Application manual