ABB REG316 4 Series Operating Instructions Manual page 406

ABB Switzerland Ltd
Settings for a solidly grounded system:
I = 0.25 I = 0.25 A
N
(The setting I = 0.1·I
grounded system.)
Stabilising resistor
D
U 60
³ = =
R
S
I 0 25 .
Chosen
Check of the overvoltage at maximum fault current
I 3
1 N
= =
I
F
+
2 x x
sys sys 0
1
=
I 100 000 ,
2
1000 ,
D U
= R I = 300 x 100 = 30,000 V
i S 2
= D
U 2 2 U (
max k
=
2 2 200 ( 30
Since this value exceeds the permissible maximum peak value
of 2,000 V, a non-linear resistor must be connected across the
circulating current circuit to limit the voltage. Shorting contacts
may also be necessary.
C.t specification:
Rated currents
Winding resistance
Knee-point voltage
Magnetising current
i.e. I
The c.t's must conform to British Standard 3938, Class X.
The c.t's should also:
have evenly distributed secondary windings on a toroidal
·
core (i.e. to minimise the secondary leakage flux)
not have any winding correction.
·
4-8
REG 316*4 1MRB520049-Uen / Rev. B
is usually chosen for a impedance
N
W
240
R = 300 W
S
´
3 1000
=
100 , 000
+
. 0 02 . 0 01
=
100 A
-
U U )
i k
- =
, 000 200 ) , 6 905
1000/1 A
£ 5 W
R
2
U = 200 V
k
£ 2% I
I
2m 2N
£ 0.02 A
2m
A
V
at U = 60 V
2