ABB Relion REG670, Applications Manual

Page: 211 / 780

Consider the possible enlarging factor that might exist due to fault infeed from
adjacent lines. Equation
60 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
(Equation 60)
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.
8.2.3.5 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 the 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-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
85 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
(Equation 61)
X
0E
X
0
X
m0
+ =
EQUATION554 V1 EN
(Equation 62)
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:
1MRK 502 071-UEN -
Section 8
Impedance protection
Generator protection REG670 2.2 IEC and Injection equipment REX060, REX061, REX062 205
Application manual