ABB REC650 ANSI, Technical Manual

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8.1.7.2 Time delay
The time delay for SAPTUF (81) is a settable definite time delay, specified by the setting
tDelay .
Trip signal issuing requires that the under frequency condition continues for at least the
user set time delay. If the PICKUP ceases during the delay time, and is not fulfilled again
within a defined reset time, the PICKUP output is reset.
When the measured frequency returns to the level corresponding to the setting
RestoreFreq , a 100ms pulse is given on the output RESTORE after a settable time delay
( tRestore ).
8.1.7.3 Blocking
It is possible to block underfrequency protection SAPTUF (81) completely, by binary
input signal:
BLOCK: blocks all outputs
If the measured voltage level decreases below the setting of MinValFreqMeas in the
preprocessing function both the PICKUP and the TRIP outputs are blocked.
8.1.7.4 Design
The design of underfrequency protection SAPTUF (81) is schematically described in
figure
79 .
Figure 80: Simplified logic diagram for SAPTUF (81)
8.1.8 Technical data
Table 139: SAPTUF (81) Technical data
Function Range or value Accuracy
Operate value, pickup function (35.00-75.00) Hz ± 2.0 mHz at
symmetrical three-
phase voltage
Operate value, restore frequency (45 - 65) Hz ± 2.0 mHz
Reset ratio <1.001 -
Operate time, pickup function At 50 Hz: 200 ms typically at f
set
+0.5 Hz to f
set
-0.5 Hz
At 60 Hz: 170 ms typically at f
set
+0.5 Hz to f
set
-0.5 Hz
-
Table continues on next page
Section 8
1MRK 511 287-UUS A
Frequency protection
194
Technical manual