ABB REG316 4 Series - Page 312

ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-274
E. Setting instructions
Protection function enable ‘I-Start’
The IDMT function starts to run when the current applied to the
function exceeds the setting ‘I-Start’. ‘I-Start’ is normally set to
1.1 I
B
.
Choice of tripping characteristic ‘c’
The shape of the IDMT characteristic is determined by the con-
stant ‘c’.
The standard IDMT characteristics according to BS 142 are:
“normal inverse” : c = 0.02
“very inverse” and “long time earth fault” : c = 1.00
“extremely inverse” : c = 2.00
Fig. 3.5.27.1 IDMT tripping characteristic for ‘I0-Invers’ (I = 3 I
0
)
“c-Setting” can also be set to “RXIDG”, in which case the func-
tion’s inverse characteristic corresponds to that of the relay Type
RXIDG:
t [s] = 5.8 – 1.35 In (I/I
B
)
The parameter “k1-Setting” has no influence in this case.