Settings; Operation Principle; Measurement Principle; Time Delay - ABB RET650 Technical Manual

Section 10
Frequency protection
10.3.5
Table 166: SAPFRC Group settings (basic)
Name
Operation
StartFreqGrad
tTrip
RestoreFreq
tRestore
10.3.6
10.3.6.1
10.3.6.2
240

Settings

Values (Range) Unit
Off -
On
-10.00 - 10.00 Hz/s
0.000 - 60.000 s
45.00 - 65.00 Hz
0.000 - 60.000 s

Operation principle

Rate-of-change frequency protection SAPFRC is used to detect fast power system
frequency changes at an early stage. It has a settable definite time delay.To avoid an
unwanted trip due to uncertain frequency measurement at low voltage magnitude, a
voltage controlled blocking of the function is available from the preprocessing
function that is, if the voltage is lower than the set blocking voltage in the
preprocessing function, the function is blocked and no START or TRIP signal is
issued. If the frequency recovers, after a frequency decrease, a restore signal is issued.

Measurement principle

The rate-of-change of the fundamental frequency of the selected voltage is measured
continuously, and compared with the set value(StartFreqGrad). If the voltage
magnitude decreases below the setting MinValFreqMeas in the preprocessing
function, which is set as a percentage of a global base voltage parameter, SAPFRC is
blocked and the output BLKDMAGN is issued. The sign of the setting
StartFreqGrad, controls if SAPFRC reacts on a positive or on a negative change in
frequency. If SAPFRC is used for decreasing frequency that is, the setting
StartFreqGrad has been given a negative value, and a trip signal has been issued, a
100 ms pulse is issued on the RESTORE output, when the frequency recovers to a
value higher than the setting RestoreFreq. A positive setting of StartFreqGrad, sets
SAPFRC to START and TRIP for frequency increases.
To avoid oscillations of the output START signal, a hysteresis has been included.

Time delay

SAPFRC has a settable definite time delay, tTrip.
Trip signal issuing requires that SAPFRC condition continues for at least the user set
time delay, tTrip. If the START condition, ceases during the delay time and is not
Step Default
- Off
0.01 0.50
0.001 0.200
0.01 49.90
0.001 0.000
1MRK 504 135-UEN A
Description
Operation Off / On
Frequency gradient start value, the sign
defines direction
Operate time delay in positive / negative
frequency gradient mode
Restore is enabled if frequency is above
set frequency value
Restore time delay
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