84-50 9424200996
Settings Calculation Examples BE1-11m
Figure 84-63. Protection, Frequency Screen
Overfrequency (81-2)
The 81-2 protection element alarms when the source frequency is 5 percent above nominal. A time delay
of 100 ms is used to avoid nuisance alarms. The pickup setting is calculated in Equation 84-46.
=
(
100 + 5%
)
= 1.05 60 = 63
Equation 84-46. 81-2 Pickup
Select Over mode, set the Pickup setting to 63 Hz, and set the Time Delay to 100 ms as shown in Figure
84-63.
Protection - Incomplete Sequence (48)
The 48 protection element is used as backup protection to the 49TC and 50 elements. The incomplete
sequence protection element monitors the starting time and returns the motor to the off state if the
starting sequence is not completed within a predetermined time. Motor start and motor run status is
provided to the 48 element from the motor status logic element in BESTlogicPlus. For an incomplete start,
the 48 element times out based on the time it takes the motor to drop below the starting mode condition.
One or two seconds should be added after the nominal start time to trip the motor. The time interval is
calculated in Equation 84-47.
=
+ 2 = 2.42 + 2 = 4.42
Equation 84-47. 48 Time Interval
Enable the 48 element and set the Time Interval to 4.42 seconds as shown in Figure 84-64.
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