ABB ret650 - Design

fulfilled again within a defined reset time, the START output is reset after the reset
time has elapsed.
After an issue of the TRIP output signal, the RESTORE output of SAPFRC is set after
a time delay (tRestore), when the measured frequency has returned to the level
corresponding to RestoreFreq. If tRestore is set to 0.000 s the restore functionality is
disabled, and no output will be given. The restore functionality is only active for
lowering frequency conditions and the restore sequence is disabled if a new negative
frequency gradient is detected during the restore period.
10.3.6.3 Design
IEC08000009_en_1.vsd
RESTORE
START
START
TRIP
Start
&
Trip
Output
Logic
BLOCK
Frequency
100 ms
Comparator
If
[StartFreqGrad<0
AND
df/dt < StartFreqGrad]
OR
[StartFreqGrad>0
AND
df/dt > StartFreqGrad]
Then
START
Comparator
f > RestoreFreq
OR
Definite Time Delay
tTrip
tRestore
BLKDMAGN
Rate-of-Change
of Frequency
BLOCK
freqNotValid
IEC08000009 V1 EN
Figure 109: Schematic design of Rate-of-change frequency protection SAPFRC
1MRK 504 135-UEN A Section 10
Frequency protection
241
Technical manual