APPENDIX
82
NA011 - Manual - 05 - 2022
Residual overcurrent 50N/51N - Moderately inverse time curve (ANSI/IEEE type MI)
F_51N-ANSIMI-Char.ai
1.1
2
3
4
5
6 7 8 9 10
20
I
E
/
I
E
>inv
I
E
/
I
E
>>inv
0.01
0.1
1
10
100
1000
10000
t
[s]
10 s
60 s
t
E
>
inv
t
E
>>
inv
5 s
1 s
0.02 s
0.2 s
0.1 s
0.5 s
t
=
t
E
>
inv
·
[(
I
E
/
I
E
>
inv
)
0.02
-1]
0.01
+ 0.023
t
=
t
E
>>
inv
·
[(
I
E
/
I
E
>>
inv
)
0.02
-1]
0.01
+ 0.023
Note: match of operating and setting time takes place when I
E
/I
E
>
inv
or I
E
/I
E
>>
inv
= 1.664