ABB Relion 650 Series Technical Manual page 263

1MRK 506 326-UUS B
(81) gets blocked, and the output BLKDMAGN is issued. All voltage settings are made in percent of
the setting of the global parameter
To avoid oscillations of the output PICKUP signal, a hysteresis has been included.
8.1.7.2 Time delay
The time delay for SAPTUF (81) is a settable definite time delay, specified by the setting
Trip signal issuing requires that the under frequency condition continues for at least the user set
time delay. If the PICKUP condition, with respect to the measured frequency ceases during the
delay time, and is not fulfilled again within a defined reset time, the PICKUP output is reset.
On the RESTORE output of SAPTUF (81) a 100 ms pulse is issued, after a time delay corresponding
to the setting of
RestoreFreq .
setting
8.1.7.3 Blocking
It is possible to block underfrequency protection SAPTUF (81) completely, by binary input signal:
BLOCK:
If the measured voltage level decreases below the setting of
function, both the PICKUP and the TRIP outputs, are blocked.
8.1.7.4 Design
The frequency measuring element continuously measures the frequency of the positive sequence
voltage and compares it to the setting
transients due to switchings and faults in the power systems. When the frequency has returned
back to the setting of
The design of Under frequency protection SAPTUF (81) is schematically described in figure 131.
Line distance protection REL650
Technical manual
VBase .
tRestore , when the measured frequency returns to the level corresponding to the
blocks all outputs
PUFrequency . The frequency signal is filtered to avoid
RestoreFreq , the RESTORE output is issued after the time delay tRestore .
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Frequency protection
MinValFreqMeas in the preprocessing
Section 8
M13354-10 v4
tDelay .
M13354-50 v4
M13354-63 v5
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