ABB REG316 4 Series Operating Instructions Manual page 683

ABB Switzerland Ltd
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 : nominal current related to the protected object
N
and 2.
the dependence of the curves of fig 1 and 2, where:
for fault currents £ 3 * I
n'
16
14
12
10
8
6
4
2
0
0 3 4
with 50% remanence
Figure 1: Transformer with 2 windings
n'
35
30
25
20
15
10
5
0
0 3 4
with 50% remanence
Figure 2: Transformer with 3 windings
the CT's should not saturate
N
6 8 10
without remanence
6 8 10 12
without remanence
12 14 16 18
14 16 18
CH-ES 30-32.10-E
20
IK/IN
20
IK/IN
3/3