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Table 10.34 – Underfrequency stages f< and f<<
Frequency measuring area
Current and voltage meas. range
Frequency stage setting range
Low voltage blocking
Definite time function:
-operating time
Undervoltage blocking
Starting time
Reset time
Reset ratio
Reset ratio (LV block)
Inaccuracy:
- starting
- starting (LV block)
- operating time
This is the instantaneous time i.e. the minimum total operational time including the fault
detection time and operation time of the trip contacts.
NOTE: Frequency measurement functions when secondary voltage
is over 5 V. f> If device restarts for some reason there will be no trip
even if the frequency is below the set limit during the start up (Start
and trip is blocked). To cancel this block, frequency has to visit
above the set limit.
Table 10.35 – Rate of change of frequency (ROCOF) stage df/dt> (81R)
Pick-up setting df/dt
Definite time delay (t> and t
> are equal):
Min
- operating time t>
Inverse time delay (t> is more than t
- minimum operating time t
>
Min
Starting time
Reset time
Inaccuracy:
- starting
- operating time(overshoot ≥ 0.2 Hz/s)
This is the instantaneous time i.e. the minimum total operational time including the fault
detection time and operation time of the trip contacts.
Technical Data
16.0 - 75.0 Hz
45.0 – 65.0 Hz
40.0 – 64.0 Hz
10 – 100 %Un
0.10
- 300.0 s (step 0.02 s)
2 – 100 %
<90 ms
<110 ms
1.002
0.5 V or 1.03 (3%)
±20 mHz
3% of the set value
±1% or ±30 ms
0.2 – 10.0 Hz/s (step 0.1 Hz/s)
0.14
– 10.00 s (step 0.02 s)
>):
Min
0.14
– 10.00 s (step 0.02 s)
140 ms
t>
±0.1 Hz/s
±1% or ±30 ms
857-UM001A-EN-P – July 2009
10-15
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