ABB REG316 4 Series Operating Instructions Manual page 138

ABB Switzerland Ltd
Multiplier 'k1-Setting'
The multiplier 'k1-Setting' enables the IDMT characteristic cho-
sen by the setting of parameter c to be shifted without changing
its shape. This is used for grading the operating times of a series
of IDMT relays along a line to achieve discrimination.
For example, in the case of the "very inverse" characteristic, the
constant c = 1 and the factor k1 £ 13.5. The operating time t is
given by the equation
k 1
=
t
I
-
1
I
B
Assuming a grading time of 0.5 s at 6 times the base current I
required, the factor k1 for each of the relays is given by
k1 = 5 t.
This produces for operating times between 0.5 and 2.5 s the fol-
lowing settings for k1:
t [s]
0.5
1
1.5
2
2.5
The characteristics according to BS 142 are set as follows:
"normal inverse"
"very inverse"
"extremely inverse"
"long time earth fault"
3-100
REG 316*4 1MRB520049-Uen / Rev. F
k1 [s]
2.5
5
7.5
10
12.5
: k1 = 0.14 s
: k1 = 13.5 s
: k1 = 80 s
: k1 = 120 s.
is
B