There are two general applications which can best utilize under power factor
protection; power-factor control and loss of excitation.
When applying the function for power-factor control, both the start value and the
start reset value should be the same sign (positive/negative) as well as the same
direction (leading/lagging). Additionally, the absolute value of the start reset value
should be greater than or equal to the absolute value of the start value. This allows
the function to properly control any power factor controls within the system.
When applying the function for loss of excitation, both the start value and the start
reset value should be the same sign (positive/negative), but the directions should
be different (leading/lagging). This application is well-suited to protect against
back-spinning. In this case the start reset value will only come into play once the
system provides power in the opposite quadrant of the start value, for example,
lagging PF turns to leading PF.
4.8.4.7 Signals
MPUPF Input signals
Table 1020: MPUPF Input signals
Name Type Default Description
I3P SIGNAL - Three-phase currents
U3P SIGNAL - Three-phase voltages
BLOCK BOOLEAN 0=False Block signal for acti-
vating the blocking
mode
DISABLE BOOLEAN 0=False Signal to block the
function during ma-
chine startup
MPUPF Output signals
Table 1021: MPUPF Output signals
Name Type Description
OPERATE BOOLEAN Operate
START BOOLEAN Start
ALARM BOOLEAN Alarm
4.8.4.8 MPUPF Settings
Table 1022: MPUPF Group settings (Basic)
Parameter
Values (Range) Unit Step Default Description
Start value Dir
1=Lagging
1=Lagging PF direction for
start value
Table continues on the next page
1MRS759142 F Protection functions
REX640
Technical Manual
1083
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