ABB REG316 4 Series, Operating Instructions Manual

Page: 171 / 980

REG 316*4 1MRB520049-Uen / Rev. F
ABB Switzerland Ltd
3-133
Note:
Because of the voltage drop of the v.t’s, the voltage does not
reach 520 V at the full E/F current, but only 360 V. The setting of
the protection must therefore be modified as follows:
Overvoltage setting
0 05
360
520
0 034 . .
=
(3.4 % U
N
instead of 5 % U
N
)
Example 5
U
GN
= 27 kV; U
HV
= 400 kV; C
12
= 3 x 10
-9
F; x = 314 1/s
HV system solidly grounded
I
E
= 15 A
U
U
V
n
GN
1
3
27000
3
15600
= = =
R
U
U
e
n
n min
³
´
æ
èç
ö
ø÷ =
´ ´
-
27000
3 15
3
15600
27 10
2
2
6
2
2
R
U
U
e
n
n max
.
£
´
´ ´ ´ ´
æ
èç
ö
ø÷ =
´ ´
-
-
0 05 27
6 314 3 10
400
6
3
15600
132 10
9
2
2
6
2
2
I
e
= 250 A (chosen)
U V
n 2
15600
15
3 300
260 =
´
=
The resistor R
e
is chosen according to R
emin
:
R
e
= 27 ´ 10 -6 ´ 260 2 = 1.825 W
R
e
I
e
= 1.825
´
300 = 547 V
3 U
2n
= 3
´
260 = 780 V
S = 3
´
260
´
300 = 135
´
10 3 VA
The specification and the modification of the protection setting is
similar to Example 4.