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2.1 PROTECTION FUNCTIONS
The DFF relay incorporates 8 underfrequency units. All frequency units are supervised by a voltage unit that inhibits
the frequency units in case the voltage decreases below the threshold.
The main settings for the frequency elements are:
GENERAL SETTINGS GROUP (Common to all Protection Functions of the relay)
RELAY STATUS
FREQUENCY
NOMINAL VOLTAGE
INHIBIT V
SEMICYCLES SET
SEMICYCLES RESET
PHASE VT RATIO
GROUND VT RATIO
SETTINGS FOR EACH INDIVIDUAL FREQUENCY ELEMENT (for example 81 N1)
NOTE: The measuring resolution of the DFF equipment is always better than 5 mHz. However to avoid fluctuations
on the LCD display, the frequency is displayed in steps of 10 mHz. Measurements in 5 mHz steps are reflected on
the oscillogram.
8
OPERATING PRINCIPLES
Name
Name
FUNCTION TYPE
81 PICKUP
TIME DELAY
-10.00 to -0.10 Hz/s
dF/dT
RESET TIME
DFF Digital Feeder Relay
Limits
NO SERV / IN SERV
50 / 60 Hz
90 – 220 Vac
40 – 110 %
3 – 20
0 – 4
1 – 4000
1 – 4000
Limits
Default
FREQ. Or dF/dT
40.00 – 70.00 Hz
0.00 - 60.00 s
- 0.75 Hz/s
0.00 - 600.00 s
2.1.1 FREQUENCY UNITS
Default
Step
NO SERV
N/A
50
N/A
90
1
40 %
1
3
1
0
1
1000
1
1000
1
Step
FREQ.
N/A
50 Hz
0.01 Hz
1.00 s
0.01 s
0.01 Hz/s
0.00 s
0.01 s
GEK-106166E
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