ABB RET670 - Setting Parameters

place very quickly, and there might not be enough time to wait until the frequency
signal has reached an abnormal value. Actions are therefore taken at a frequency level
closer to the primary nominal level, if the rate-of-change frequency is large (with
respect to sign).
SAPFRC (81)PICKUP value is set in Hz/s. All voltage magnitude related settings are
made as a percentage of a settable base voltage, which normally is set to the primary
nominal voltage level (phase-phase) of the power system or the high voltage equipment
under consideration.
SAPFRC (81) is not instantaneous, since the function needs some time to supply a
stable value. It is recommended to have a time delay long enough to take care of signal
noise. However, the time, rate-of-change frequency and frequency steps between
different actions might be critical, and sometimes a rather short operation time is
required, for example, down to 70 ms.
Smaller industrial systems might experience rate-of-change frequency as large as 5 Hz/
s, due to a single event. Even large power systems may form small islands with a large
imbalance between load and generation, when severe faults (or combinations of faults)
are cleared - up to 3 Hz/s has been experienced when a small island was isolated from
a large system. For more "normal" severe disturbances in large power systems, rate-of-
change of frequency is much less, most often just a fraction of 1.0 Hz/s.
3.9.3.3 Setting parameters
Table 141: SAPFRC (81) Group settings (basic)
Name
Values (Range) Unit Step Default Description
Operation Disabled
Enabled
- - Disabled Disable/Enable Operation
VBase 0.05 - 2000.00 kV 0.05 400.00 Base setting for the phase-phase voltage in kV
PUFreqGrad -10.00 - 10.00 Hz/s 0.01 0.50 Frequency gradient start value. Sign defines
direction.
IntBlockLevel 0 - 100 %VB 1 50 Internal blocking level in % of VBase.
tTrip 0.000 - 60.000 s 0.001 0.200 Operate time delay in pos./neg. frequency
gradient mode.
RestoreFreq 45.00 - 65.00 Hz 0.01 49.90 Restore frequency if frequency is above
frequency value (Hz)
tRestore 0.000 - 60.000 s 0.001 0.000 Restore time delay.
tReset 0.000 - 60.000 s 0.001 0.000 Time delay for reset.
Section 3 1MRK504116-UUS C
IED application
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Application manual