90
95
100
0
0.5
1
en05000075_ansi.vsd
T
im
eD
ly
O
pe
ra
te
[
s]
V [% of VBase]
Exponenent
0
1
2
3
4
ANSI05000075 V1 EN-US
Figure 362: Voltage dependent inverse time characteristics for underfrequency protection
SAPTUF (81). The time delay to trip is plotted as a function of the measured
voltage, for the Exponent = 0, 1, 2, 3, 4 respectively.
10.1.7.4
Blocking
M13354-50 v6
It is possible to block underfrequency protection SAPTUF (81) partially or completely, by binary
input signals or by parameter settings, where:
BLOCK:
blocks all outputs
BLKTRIP:
blocks the TRIP output
BLKREST:
blocks the RESTORE output
If the measured voltage level decreases below the setting of
MinValFreqMeas in the preprocessing
function both the PICKUP and the TRIP outputs are blocked.
10.1.7.5
Design
M13354-63 v9
The frequency measuring element continuously measures the frequency of the positive sequence
voltage and compares it to the setting
PUFrequency. The frequency signal is filtered to avoid
transients due to switchings and faults. The time integrator can trip 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 (81) is schematically described in figure
1MRK 502 066-UUS B
Section 10
Frequency protection
669
Technical manual
Содержание Relion 670 series
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