ABB REG316 4 Series - Page 166

ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-128
HEST 905 032 C
Step-up transformer
3 C
I
E
U /U
U>
R
3n 4n
U /U
1n 2n
e
I
e
I
E
I
m
a
x
LV
GN
1
U
Generator
I
E
HV
U
2
3 C
12
HV
E
Fig. 3.5.11.5 Stator E/F protection with a grounding
transformer at the star-point
Example 2
U
GN
= 12 kV; I
C
= 10 A
I
Emax
= I
C
= 10 A
UV
n1
12000
3
6930
==
I
1n
= 10 A
U
2n
= 200 V
I
2n
= I
e
= 10
6930
200
346= A
R
e
=
´
=
200
6930 10
0 577
2
. W
S
n
= U
1n
I
1n
= 6930 ´ 10 ³ 70 kVA
Specification:
1 grounding transformer 70 kVA; 10 s; 50 Hz
6930/200 V; 10/346 A
1 resistor 0.577
W; 346 A; 10 s
1 interposing v.t. 10 VA; 50 Hz; 200/100 V
(only necessary if U
2n
> 100 V)