ABB REG316 4 Series - Page 261

REG 316*4 1MRB520049-Uen / Rev. F ABB Switzerland Ltd
3-223
where
I
GN
: rated current of the protected unit
I
N1
, I
N2
: rated primary and secondary c.t. currents.
The current referred to the rated current I
N
of the protection is:
i
I
I
I
I
I
I
R
R
N
GN
N
N2
N
== ´
1
The steady-state temperature rise becomes:
DJ
W
GN
N
N2
N
I
I
I
I
=´
æ
è
ç
ö
ø
÷
´
1
2
100%
At a constant current, the tripping time is:
[]
[]
÷
÷
÷
÷
÷
ø
ö
ç
ç
ç
ç
ç
è
æ
÷
÷
ø
ö
ç
ç
è
æ
´-J
÷
÷
ø
ö
ç
ç
è
æ
´-J
t=
2
B
2
B
0
I
I
100%
I
I
100%
lnt
where
J
0
: initial temperature rise
J : pick-up temperature rise
t : thermal time constant.
The variables in the submenu ‘DISPLAY OPERATING VALUES’
are the calculated temperature rise, the power dissipation and
the current. The first two are mean values over the period of
calculation (=
t / 40).
The values shown in the event list is the power dissipation at the
instant of tripping.
Example:
Rated current of the protected unit I
GN
= 8000 A
C.t. ratings I
N1
= 10000 A
I
N2
=5 A
Rated relay current I
N
= 5 A