APPENDIX
163
NA30 - Manual - 04 - 2022
Phase overcurrent 50/51 - Very inverse time curve (IEC 60255-3/BS142 type B)
F_51-IECB-Char.ai
1.1
2
3
4
5
6 7 8 9 10
20
I
/
I
>inv
0.01
0.1
1
10
100
1000
10000
t
[s]
t
>
inv
= 10 s
t
>
inv
= 60 s
t
>
inv
= 5 s
t
>
inv
= 1 s
t
>
inv
= 0.5 s
t
>
inv
= 0.2 s
t
>
inv
= 0.02 s
t
>
inv
= 0.1 s
t
=
t
>
inv
·
[(
I
/
I
>
inv
) -1]
13.5
Note: match of operating and setting time takes place when I/I>
inv
= 14.5
