APPENDIX
178
NA30 - Manual - 04 - 2022
Ground directional overcurrent 67N - Moderately inverse time curve (ANSI/IEEE type MI)
F_67N-ANSIMI-Char.ai
1.1
2
3
4
5
6 7 8 9 10
20
I
ED
/
I
ED
>inv
0.01
0.1
1
10
100
1000
10000
t
[s]
t
ED
>
inv
=
10 s
t
ED
>
inv
=
60 s
t
ED
>
inv
=
5 s
t
ED
>
inv
=
1 s
t
ED
>
inv
= 0.02 s
t
ED
>
inv
= 0.2 s
t
ED
>
inv
= 0.1 s
t
ED
>
inv
= 0.5 s
t
=
t
ED
>
inv
·
[(
I
ED
/
I
ED
>
inv
)
0.02
-1]
0.01
+ 0.023
Note: match of operating and setting time takes place when I
ED
/I
ED
>
inv
= 1.664