Nominal method example
A GENSET controller controls a genset with a nominal current of 100 A. The L1 current is 80 A, the L2 current is 90 A, and
the L3 current is 60 A.
The current unbalance is (90 A - 60 A) / 100 A = 0.3 = 30 %.
3.4.10 Directional over-current (ANSI 67)
Protection IEC symbol (IEC60617) ANSI (IEEE C37.2) IEC 61850 Operate time
Directional over-current 67 PTOC < 100 ms
The alarm response is based on the highest phase current true RMS value, with the direction
from the active power from the source, as measured by the controller.
Controller types: These alarms are present in GENSET controllers.
Configure the parameters under Configure > Parameters > [Source] > Current protections > Directional over-current #, where
# is 1 or 2*.
Table 3.38
Default parameters
Parameter Range Directional over-current 1 Directional over-current 2
Set point -300 to 300 % of nominal current 110 % 130 %
Delay 0.00 s to 1 h 0.10 s 0.10 s
Enable Not enabled, Enabled Not enabled Not enabled
Action Warning Warning
INFO
For a positive set point, the alarm trigger level is High. When a negative set point is written to the controller, then the
controller automatically changes the alarm trigger level to Low.
3.4.11 Inverse time over-current (ANSI 51)
Protection
IEC symbol (IEC60617) ANSI (IEEE C37.2) IEC 61850 Operate time
Inverse time over-current It> 51 PTOC -
DESIGNER'S HANDBOOK 4189340911K UK Page 68 of 521
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