ABB REG316 4 Series Operating Instructions Manual page 100

ABB Switzerland Ltd
E. Setting instructions
Settings:
Setting
Delay
Over or undercurrent
Number of phases
Setting I-Setting
The current setting 'I-Setting' must be sufficiently high on the one
hand to avoid any risk of false tripping or false signals under
normal load conditions, but should be low enough on the other to
detect the lowest fault current that can occur. The margin which
has to be allowed between the maximum short-time load current
and the setting must take account of:
the tolerance on the current setting
·
the reset ratio.
·
The maximum short-time load current has to be determined ac-
cording to the power system conditions and must take switching
operations and load surges into account.
I
I-Setting
I
I
N
Fig. 3.5.3.1 Operating characteristic of the definite time over-
current function
3-62
REG 316*4 1MRB520049-Uen / Rev. F
I-Setting
Delay
MaxMin
NrOfPhases
Delay
HEST 905 010 C