Measurement Principle; Time Delay - ABB REG650 Technical Manual

Section 9
Frequency protection
9.3.6.1
9.3.6.2
264

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 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, 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

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, with respect to the measured
frequency ceases during the delay time, and is not fulfilled again within a defined
reset time, the START output is reset after the reset time has elapsed.
The RESTORE output of SAPFRC is set, after a time delay equal to the setting of
tRestore, when the measured frequency has returned to the level corresponding to
RestoreFreq, after an issue of the TRIP output signal. 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, defined by the settings RestoreFreq and tRestore.
1MRK 502 034-UEN -
Technical Manual