102
1MRS751802-MUM
Protection Relay
Technical Reference Manual, Standard Configurations
REX 521
7.1.12.
f1 and f2
The frequency function blocks operate as either underfrequency or overfrequency
protection depending on whether the set operate value is above or below the rated
frequency of the relay. The operation is insensitive to harmonics and the DC
component.
Fig. 7.1.12.-1
Function block symbol of f1 and f2
Start time
Injected voltages > 2.0 x start voltage:
internal time < 32 ms
total time < 40 ms
Reset time
40...1000 ms
(Depends on the minimum pulse width set
for the trip output)
Reset ratio, typically
0.95
Retardation time
< 50 ms
Operate time accuracy in DT mode
±2% of set value or ±20 ms
Residual over voltage protection, low-set stage, Uo>, high-set stage, Uo>> and
instantaneous stage, Uo>>> (Continued)
System frequency protection, f1 and f2
Voltage limit
0.30...0.90 x Un
Start frequency
25.00...75.00 Hz
Operate time 1
0.10...120.00 s
Start df/dt
0.2...10.0 Hz/s
Operate time 2
0.12...120.00 s
Operation mode
Not in use
f</f> 1 timer
f</f> 2 timers
f</f> OR df/dt>
f</f>AND df/dt>
f</f> OR df/dt<
f</f>AND df/dt<
Accuracy for the f</f> function is defined in the setting
range 25...75 Hz.
Operation accuracy
Frequency function (f</f>): ± 10 mHz
Frequency rate of change function (df/dt):
real df/dt < ± 5 Hz/s: accuracy ±100 mHz/s
real df/dt < ± 15 Hz/s: accuracy ±2.0% of the real df/dt
Undervoltage blocking: ±1.0% of set value
Start time
Total start times at rated freq. fn = 50 Hz:
Frequency measurement: < 100 ms
Df/dt measurement: < 120 ms
Note! The operate times and start times are specified for
the set rated frequencies 50 Hz and 60 Hz.
BS1
BS2
GROUP
RESET
START1
TRIP1
START2
TRIP2
f1
f<
f>
df/dt<
df/dt>
BS1
BS2
GROUP
RESET
START1
TRIP1
START2
TRIP2
f2
Freq1St2
f<
f>
df/dt<
df/dt>
Summary of Contents for REX 521
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