CHAPTER 1: INTRODUCTION SPECIFICATIONS
869 MOTOR PROTECTION SYSTEM – INSTRUCTION MANUAL 1–19
UNDERFREQUENCY (81U)
Pickup Level:..........................................................20.00 to 65.00 Hz in steps of 0.01
Dropout Level: ......................................................Pickup + 0.03 Hz
Pickup Time Delay:.............................................0.000 to 6000.000 s in steps of 0.001s
Dropout Time Delay: .........................................0.000 to 6000.000 s in steps of 0.001s
Minimum Operating Voltage: ........................0.000 to 1.250 x VT in steps of 0.001 x VT
Minimum Operating Current: ........................0.000 to 30.000 x CT in steps of 0.001 x CT
Level Accuracy:....................................................± 0.001 Hz
Timer Accuracy: ..................................................± 3% of delay setting or ± ¼ cycle (whichever is greater)
from pickup to operate
Operate Time:.......................................................typically 7.5 cycles at 0.1 Hz/s change
typically 7 cycles at 0.3 Hz/s change
typically 6.5 cycles at 0.5 Hz/s change
FAST PATH:
Typical times are average Operate Times including variables such as frequency change
instance, test method, etc., and may vary by ± 0.5 cycles.
UNDERPOWER
Operating Condition:.........................................Three-phase real power
Number of Elements: ........................................1, alarm and trip stages
Trip/Alarm Pickup Level: ..................................1 to 25000 kW in steps of 1
Pickup Level Accuracy: ....................................±1.0% of reading
Hysteresis:..............................................................3%
Trip/Alarm Pickup Delay:.................................0 to 180.00 s in steps of 0.01
Timer Accuracy: ..................................................±3% of delay time or ±10 ms, whichever is greater, pick up to
operate
Operate Time:.......................................................<45 ms at 60 Hz; <50 ms at 50 Hz (NOTE 1)
VOLTS PER HERTZ (24)
Voltages:..................................................................Phasor only
Pickup Level:..........................................................0.80 to 4.00 in steps of 0.01 pu
Dropout Level: ......................................................97 to 98% of pickup
Level Accuracy:....................................................±0.02 pu
Timing Curves: .....................................................Definite Time; IEC Inverse A/B/C; FlexCurves A, B, C, and D
TD Multiplier: .........................................................0.05 to 600.00 s in steps of 0.01
Reset Delay:...........................................................0.00 to 6000.000 s in steps of 0.01
Timer Accuracy: ..................................................±3% of operate time or ±15 cycles (whichever is greater) for
values greater than 1.1 x pickup
Number of Elements: ........................................2
Number of Elements: ........................................1
(NOTE 1) When the setpoint “Motor Load Filter Interval” is programmed as non-zero, it
might increase the trip/alarm times by 16.7 ms (or 20 ms at 50 Hz) for each additional
cycle in the filter interval for the following protection elements: Acceleration Time, Current
Unbalance, Mechanical Jam, Overload Alarm, Thermal Model, Undercurent, Power Factor,
and Underpower.
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