Measurement Principle - ABB RES670 Technical Manual

1MRK 511 408-UUS A
10.3.6.1
10.3.6.2
10.3.6.3
Phasor measurement unit RES670 2.2 ANSI
Technical manual
no PICKUP 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, PUFreqGrad. Rate-of-change
frequency protection SAPFRC (81) is also dependent on the voltage magnitude. If the
voltage magnitude decreases below the setting IntBlockLevel, SAPFRC (81) is
blocked, and the output BLKDMAGN is issued. The sign of the setting PUFreqGrad,
controls if SAPFRC (81) reacts on a positive or on a negative change in frequency. If
SAPFRC (81) is used for decreasing frequency that is, the setting PUFreqGrad 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 PUFreqGrad, sets SAPFRC (81) to
PICKUP and TRIP for frequency increases.
To avoid oscillations of the output PICKUP signal, a hysteresis has been included.
Time delay
Rate-of-change frequency protection SAPFRC (81) has a settable definite time delay,
tDelay.
Trip signal issuing requires that the rate-of-change of frequency condition continues for
at least the user set time delay, tDelay. If the PICKUP condition, with respect to the
measured frequency ceases during the delay time, and is not fulfilled again within a
user defined reset time, tReset, the PICKUP output is reset, after that the defined reset
time has elapsed. Here it should be noted that after leaving the hysteresis area, the
PICKUP condition must be fulfilled again and it is not sufficient for the signal to only
return back into the hysteresis area.
The RESTORE output of SAPFRC (81) is set, after a time delay equal to the setting of
tDelay, 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.
Blocking
Rate-of-change frequency protection (SAPFRC, 81) can be partially or totally blocked,
by binary input signals or by parameter settings, where:
Section 10
Frequency protection
M14970-10 v7
M14970-23 v6
M14970-6 v8
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