ABB Modures LZ91 - Page 20

18
Line
angle
R/X =
I
R/X =
2
sPL
( 0 )
_kx
k
R
kx
0
-
I
-
5
-
0,992
-
10
-
0,985
-
15
-
0,977
-
20
-
0,968
-
21
-
0,966
1,228
25
-
0,959
1,188
30
-
0,95 1,152
35
-
0,939
1,125
40 1,104 0,927
1,104
45 1,087
-
1,087
50 1,073
-
1,073
55
1,061
-
1,061
60 1,05
-
1,05
65
1,041
-
1,041
70 1,032
-
1,032
75 1,023
-
1,023
80 1,015
-
1,015
85
1, 008.
-
1,008
90
1
-
1
Table 3.12 - Factors kx and kR in relation to 'P (a= 5°)
System voltage
P. t. ratio
C.t. ratio
Primary zone impedances
Phase-angle of line
Relay ratings
Reactance line slope
u
=
KU
KI
=
ZLpl
=
<p
IN
a
60 kV
(60
kV I {J)
I
(110 v I {3)
200
A I 5 A
40
4 Ohm,
ZLp2
=
6 Ohm,
z =
Lp3
60°
5 A,
UN
110 v
50
545.45
8 Ohm
Firstly the secondary reactances must be calculated from the primary values:
ii I
X . x--and
Lp ..
uu
The line reactances for the three zones become:
XLl = 0.254 Ohm, XL
2
0.381 Ohm, xL
3
= 0.508 Ohm
The correct.ion factor kx is:
tan 5°
1 + = 1.05
tan 60°
(