Time Delay - ABB REL650 series Technical Manual

Section 9
Frequency protection
9.1.7.2
9.1.7.3
9.1.7.4
9.1.8
320

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).
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.
Design
The design of underfrequency protection SAPTUF (81) is schematically described in
figure 147.
Figure 148: Simplified logic diagram for SAPTUF (81)
Technical data
Table 211: SAPTUF (81) Technical data
Function
Operate value, pickup function
Operate value, restore frequency
Reset ratio
Operate time, pickup function
Table continues on next page
Range or value
(35.00-75.00) Hz
(45 - 65) Hz
<1.001
At 50 Hz: 200 ms typically at f
set
-0.5 Hz
At 60 Hz: 170 ms typically at f
set
-0.5 Hz
1MRK 506 335-UUS A
Accuracy
± 2.0 mHz at
symmetrical three-
phase voltage
± 2.0 mHz
-
+0.5 Hz to f -
set
+0.5 Hz to f
set
Technical manual