ABB Switzerland Ltd REG 316*4 1MRB520049-Uen / Rev. F
3-88
E. Setting instructions
Settings:
Pick-up current I-Setting
Characteristic angle Angle
Delay Delay
Time allowed for receipt of signal tWait
Response at the end of the
memorised power direction time MemDirMode
Time during which the memorised
direction is valid MemDuration
Pick-up value I-Setting
“I-Setting” must be chosen high enough to prevent false tripping
or alarms from taking place and low enough to reliably detect the
minimum fault current. The setting must be sufficiently above the
maximum transient load current and allow for:
· c.t. and relay inaccuracies
· the reset ratio.
The maximum transient load current has to be determined ac-
cording to the power system operating conditions and take ac-
count of switching operations and load surges.
I
HEST 905 010 C
I
N
I
I-Setting
Delay
Fig. 3.5.7.1 Operating characteristic of the definite time over-
current detector
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