88 Rockwell Automation Publication 825-UM004D-EN-P - November 2012
Chapter 6 Configuring Protection & Logic Functions
For relay application on an induction motor, it is recommended that the installer
disable the elements by setting both the Negative VAR Warn Level and Negative
VAR Trip Level settings to Off.
Underpower
If the real three-phase power falls below the warning or trip level for longer
than the time delay setting, the relay can issue a warning or trip signal. The
underpower elements are disabled when the motor is stopped or starting.
Underpower elements operate in addition to the Load Loss function and you
can use them to detect motor load loss and other underpower conditions.
Disable the elements by setting the Underpower Warning Level and Underpower
Trip Level settings to Off.
Power Factor
If the measured power factor falls below the leading or lagging level for longer
than the time delay setting, the relay can issue a warning or trip signal. The power
factor elements are disabled when the motor is stopped or starting. Power factor
elements can be used to detect synchronous motor out-of-step or loss-of-field
conditions.
Refer to Power Measurement Conventions on page107 for the relay power
measurement convention.
Table 31 - Underpower Settings
Setting Prompt Setting Range Factory Default
UP TRIP LEVEL Off, 1…25000 kW Off
UP TRIP DELAY 0…240 s 1
UP WARN LEVEL Off, 1…25000 kW Off
UP WARN DELAY 0…240 s 1
NOTE: Underpower Trip and Warning Level settings are in Primary kW.
Table 32 - Power Factor Settings
Setting Prompt Setting Range Factory Default
PF LAG TRIP LEV Off, 0.05…0.99 Off
PF LD TRIP LEV Off, 0.05…0.99 Off
PF TRIP DELAY 0…240 s 1
PF LAG WARN LEV Off, 0.05…0.99 Off
PF LD WARN LEV Off, 0.05…0.99 Off
PF WARN DELAY 0…240 s 1
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