ABB Relion 670 series - Setting of Zones for Parallel Line Application

rem L
1.2 Z2 Z-
rev
Z ³ ×
EQUATION2314 V1 EN (Equation 253)
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
Parallel line in service – Setting of zone 1
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
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
115
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
(Equation 254)
X
0E
X
0
X
m0
+=
EQUATION554 V1 EN (Equation 255)
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-UUS -
Impedance protection
328 Line distance protection REL670 2.2 ANSI
Application manual