occurs on the wye-connected side of the power transformer, negative sequence
current quantities appear on the delta-connected side of the power transformer.
The most common application for the negative sequence overcurrent protection is
probably rotating machines, where negative sequence current quantities indicate
unbalanced loading conditions (unsymmetrical voltages). Unbalanced loading
normally causes extensive heating of the machine and can result in severe damages
even over a relatively short time period.
Multiple time curves and time multiplier settings are also available for coordinating
with other devices in the system.
4.4.1.7 Signals
NSPTOC Input signals
Table 735: NSPTOC Input signals
Name Type Default Description
I3P SIGNAL - Three-phase currents
BLOCK BOOLEAN 0=False Block signal for acti-
vating the blocking
mode
ENA_MULT BOOLEAN 0=False Enable signal for cur-
rent multiplier
NSPTOC Output signals
Table 736: NSPTOC Output signals
Name Type Description
OPERATE BOOLEAN Operate
START BOOLEAN Start
4.4.1.8 NSPTOC Settings
Table 737: NSPTOC Group settings (Basic)
Parameter
Values (Range) Unit Step Default Description
Start value 0.01...5.00 xIn 0.01 0.30 Start value
Start value Mult 0.8...10.0 0.1 1.0 Multiplier for scal-
ing the start value
Time multiplier 0.025...15.000 0.005 1.000 Time multiplier
in IEC/ANSI IDMT
curves
Operate delay time 40...200000 ms 10 40 Operate delay time
Operating curve
type
1=ANSI Ext. inv.
2=ANSI Very inv.
3=ANSI Norm. inv.
4=ANSI Mod. inv.
5=ANSI Def. Time
6=L.T.E. inv.
15=IEC Def. Time Selection of time
delay curve type
1MRS759142 F Protection functions
REX640
Technical Manual
823
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