ABB Modures LZ91 - Page 14

12
Settings
t(O]
OU
0
J
m
'j
0 ••• 90
90
1
1
30
90
0,57
1,04
30 108
1
1,18
(90)
(108)
(1)
(1,38)
30
108
0,57
1,22
Table 3.5 - Permissible settings in relation to a circular characteristic
Such characteristics have a considerably extended reactive reach compared
with a circle concentric to the origin. The equation for a solidly grounded
system then becomes:
u x y
=
where
1 + k
n = ----
0
- for starting (Z/// ..• I in the order number)
2
-
It_J,s pe~miss~ble to use the algebraic sum instead of the geometric sum (IA
+ IL), since it represents the worst case.
U min. phase-to-neutral voltage = 0.85 UB .
(0.85 x min. rated voltage) min
The effective reach along the line is dependent on the characteristic angle
of the line and the kind of fault (see •rables 3.6 to 3.8):
-
-
Line
Characteristic
angle
Circle Circle Lense Lense
<pL
[ 0 ]
x = x
B A
XB = 0.57
XA
x = x
B A
XB = 0.57
XA
90 1
1
1 1
80
1 1
0.94 0.94
70 1 0.99
0.89 0.88
60 1 0.97
0.85 0.82
50
1 0.94
0.81 0.76
40 1 0.91
0.78 0.70
30 1 0.87
0.76 0.66
20 1
0.83 0.74 0.61
10 1
0.79 0.73
0.59
0
1
0.76 0.73
0.55
Lens: ol = 108°
(
Table 3.6 - Relative reach in relation to characteristic and line angle for (."'
a phase-to-phase fault