ABB REG316 4 Series - Page 683

CH-ES 30-32.10-E
ABB Switzerland Ltd
3/3
n : rated overcurrent factor (ALF = accuracy limit factor)
n' : necessary effective overcurrent factor, as a function of fault current IK,
(at nominal frequency and time constant of the network)
PB : connected burden at rated current
PE : ct losses of secondary windings
Pr : rated ct burden
I
N
: nominal current related to the protected object
and 2.
the dependence of the curves of fig 1 and 2, where:
for fault currents £ 3 * I
N
the CT's should not saturate
0
2
4
6
8
10
12
14
16
0 3 4 6 8 10 12 14 16 18 20
with 50% remanence without remanence
IK/IN
n'
Figure 1: Transformer with 2 windings
0
5
10
15
20
25
30
35
0 3 4 6 8 101214161820
with 50% remanence without remanence
n'
IK/IN
Figure 2: Transformer with 3 windings