ABB REG316 4 Series - Page 170

ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-132
Example 4
U
GN
= 12 kV; U
HV
= 110 kV; C
12
= 3 x 10
-9
F; w = 314 1/s
HV system ungrounded.
I
Emax
= 15 A
U
U
V
n
GN
1
3
12000
3
6930
== =
R
U
U
e
n
nmin
..³
´
æ
è
ç
ö
ø
÷
´= ´ ´
-
12000
315
3
6930
07 060 10
2
2
4
2
2
R
U
U
e
n
nmax
.
.£
´
´´´´
æ
è
ç
ö
ø
÷
=´ ´
-
-
005 12
6 314 3 10 110
3
6930
181 10
9
2
2
4
2
2
Since from this calculation R
emax
is greater than R
emin
, the
protection is stable at the chosen current I
Emax
and the value of
the resistor R
e
can be determined in relation to R
emin
.
I
e
= 200 A
UV
n2
6930
15
3 200
173
=
´
=
It then follows that
R
emin
³ 0.60 ´ 10
-4
´ 173
2
= 1.80 W
R
emax
£ 1.81 ´ 10
-4
´ 173
2
= 5.42 W
R
e
= 1.80 W
At I
e
= 200 A, the voltage drop across the resistor R
e
is
U
R
e
= R
e
I
e
= 1.8 ´ 200 = 360 V
Neglecting load current, the maximum voltage across the broken
delta windings is:
U = 3 U
2n
= 3 ´ 173 » 520 V
Specification:
1 resistor 1.80
W; 200 A; 10 s
3 v.t’s
12000
3
173 V single-phase insulated
1 interposing v.t. 10 VA; 50 Hz; 520 / 100 V