ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-62
E. Setting instructions
Settings:
Setting I-Setting
Delay Delay
Over or undercurrent MaxMin
Number of phases NrOfPhases
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
HEST 905 010 C
I
N
I
I-Setting
Delay
Fig. 3.5.3.1 Operating characteristic of the definite time over-
current function
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