ABB REL301 - For

I.L. 40-386.3
2-2 (10/94)
is the direction where tripping takes place; the “reverse” reach is then in the forward
line direction.)
(1)
(2)
Z
0L
, Z
1L
= zero and positive sequence line impedance in relay ohms
Z
CGF
, Z
CGR
= Zone forward and reverse reach settings in secondary ohms of Z1L, for ph-
G fault (both are in angle PANG)
These units are directionally supervised by FDOG (RDOG for reverse Zone3). Because of in-
ternal clipping of unfaulted phase voltages during phase-ground faults, use of Zero-sequence
or Dual Polariz (polarization) for DIR TYPE only is recommended when applied to resis-
tance grounded systems; calculation of V2 magnitude and angle is likely to be incorrect in this
application, causing NSEQ polarization to give false directional sense ( see Section 2.4.11 ).
2.2.2 Three-Phase Fault
Three-phase (3Ø) fault detection (Figure 2-3) is accomplished by the logic operation of
one of the three ground units, plus the 3Ø fault output signal from the faulted phase
selector unit.
However, for a 3-phase fault condition, the computation of the distance units will be:
V
XG
- I
X
Z
CP
(3)
(and (V
Q
) (4)
where V
XG
=V
AG
, V
BG
, or V
CG
I
X
=I
A
, I
B
or I
C
Z
CP
= Zone reach setting (Pilot Ø, Z1Ø, Z2Ø,and Z3Ø) in secondary ohms
for multi-phase faults.
V
Q
= Quadrature phase voltages, i.e.,V
CB
, V
AC
and V
BA
for ↓A, φB and Ø
C units, respectively.
V
XG
I
X
k
O
I
O
+[]
Z
CG
–
k
o
Z
OL
Z
IL
–
Z
IL
------------------------
Z
R
GANG PANG–()∠==
I
O
1
3
---
I
A
I
B
I
C
++()=
jV
XG
I
X
k
O
I
O
+[]Z
CGR
+()
Where V
XG
V
AG
V
BG
or V
C
,,=
I
X
I
A
I
B
or I
C
,,=