Thytronic NA20, Manual, Page: 144 / 208

APPENDIX
144 NA20 - Manual - 04 - 2022
‡ Negative sequence overcurrent 46 - Very inverse time curve (IEC 60255-3/BS142 type B)
F_46-IECB-Char.ai
1.1
2 3 4 5 6 7 8 9 10 20
0.01
0.1
1
10
100
1000
10000
t [s]
I
2
/I
2
>
inv
t
2
>
inv
= 60 s
t
2
>
inv
= 10 s
t
2
>
inv
= 5 s
t
2
>
inv
= 1 s
t
2
>
inv
= 0.5 s
t
2
>
inv
= 0.2 s
t
2
>
inv
= 0.02 s
t
2
>
inv
= 0.1 s
t = t
2
>
inv
·
[( I
2
/ I
2
>
inv
)-1]
13.5
Note: match of operating and setting time takes place when I
2
/I
2
>
inv
= 14.5