Blocking; Design - ABB RED650 Technical Manual

1MRK 505 394-UEN A
10.1.6.4
10.1.6.5
Line differential protection RED650 2.2 IEC
Technical manual
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Exponenent
0.5
0
90
IEC05000075 V1 EN-US
Figure 127: Voltage dependent inverse time characteristics for underfrequency
protection SAPTUF. The time delay to operate is plotted as a
function of the measured voltage, for the Exponent = 0, 1, 2, 3, 4
respectively.

Blocking

It is possible to block underfrequency protection SAPTUF partially or completely,
by binary input signals or by parameter settings, where:
BLOCK: blocks the START, TRIP and
RESTORE outputs
BLKTRIP: blocks the TRIP output
BLKREST: blocks the RESTORE output
If the measured voltage level decreases below the setting of IntBlockLevel, both the
START and the TRIP outputs are blocked.

Design

The frequency measuring element continuously measures the frequency of the
positive sequence voltage and compares it to the setting StartFrequency. The
frequency signal is filtered to avoid transients due to switchings and faults. The
time integrator can operate either due to a definite delay time or to the special
voltage dependent delay time. When the frequency has returned back to the setting
of RestoreFreq, the RESTORE output is issued after the time delay tRestore. The
design of underfrequency protection SAPTUF is schematically described in
figure 128.
0
1
2
3
4
95
U [% of UBase]
en05000075.vsd
Section 10
Frequency protection
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M13354-50 v7
M13354-63 v10
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