Thytronic NA20, Manual, Page: 152 / 208

APPENDIX
152 NA20 - Manual - 04 - 2022
‡ Residual overcurrent 50N/51N - Extremely inverse time curve (IEC 60255-3/BS142 type C)
F_51-IECC-Char.ai
1.1
2 3 4 5 6 7 8 9 10 20
I
E
/I
E
>
inv
0.01
0.1
1
10
100
1000
10000
100000
t [s]
t
E>
inv
= 10 s
t
E>
inv
= 60 s
t
E>
inv
= 5 s
t
E>
inv
= 1 s
t
E>
inv
= 0.5 s
t
E>
inv
= 0.2 s
t
E>
inv
= 0.02 s
t
E>
inv
= 0.1 s
t = t
E
>
inv
·
[( I
E
/ I
E
>
inv
)
2
-1]
80
Note: match of operating and setting time takes place when I
E
/I
E
>
inv
= 9