ABB REG650 ANSI, Technical Manual

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10.3.5 Settings
Table 196: SAPFRC Group settings (basic)
Name Values (Range) Unit Step Default Description
Operation Off
On
- - Off Operation Off / On
StartFreqGrad -10.00 - 10.00 Hz/s 0.01 0.50 Frequency gradient start value, the sign
defines direction
tTrip 0.000 - 60.000 s 0.001 0.200 Operate time delay in positive / negative
frequency gradient mode
RestoreFreq 45.00 - 65.00 Hz 0.01 49.90 Restore is enabled if frequency is above
set frequency value
tRestore 0.000 - 60.000 s 0.001 0.000 Restore time delay
10.3.6 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.
10.3.6.1 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.
10.3.6.2 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
Section 10
1MRK 502 048-UEN A
Frequency protection
304
Technical manual