Operation Principle; Measurement Principle; Time Delay - ABB RED650 Technical Manual

1MRK 505 394-UEN A
Name Values (Range)
RestoreFreq
tRestore
tReset
Table 149: SAPFRC Non group settings (basic)
Name Values (Range)
GlobalBaseSel
10.3.6
10.3.6.1
10.3.6.2
Line differential protection RED650 2.2 IEC
Technical manual
Unit
45.00 - 65.00 Hz
0.000 - 60.000 s
0.000 - 60.000 s
Unit
1 - 12 -

Operation principle

Rate-of-change frequency protection SAPFRC is used to detect fast power system
frequency changes at an early stage. SAPFRC has a settable definite time delay. If
the rate-of-change of frequency remains below the set value, for negative rate-of-
change, for a time period equal to the chosen time delay, the TRIP signal is issued.
If the rate-of-change of frequency remains above the set value, for positive rate-of-
change, for a time period equal to the chosen time delay, the TRIP signal is issued.
To avoid an unwanted trip due to uncertain frequency measurement at low voltage
magnitude a voltage controlled blocking of the function is available, that is, if the
voltage is lower than the set blocking voltage IntBlockLevel 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. Rate-of-
change frequency protection SAPFRC is also dependent on the voltage magnitude.
If the voltage magnitude decreases below the setting IntBlockLevel, 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,
then 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

Rate-of-change frequency protection SAPFRC has a settable definite time delay,
tDelay.
Step Default
0.01 49.90
0.001 0.000
0.001 0.000
Step Default
1 1
Section 10
Frequency protection
Description
Restore frequency value
Restore time delay
Time delay for reset
Description
Selection of one of the Global Base
Value groups
M14970-3 v9
M14970-6 v8
M14970-10 v7
279