BLOCK
U_LOW
Level
detector
t
Timer
U3P
U_A_AB
U_B_BC
U_C_CA
Figure 765: Functional module diagram
Level detector
The
Voltage selection setting is used for selecting the phase-to-earth or phase-
tophase voltages for supervision.
The voltage measurement can adapt the frequency to a range of 10...70 Hz.
Level detector supports one- or three-phase operation. Selection can be made with
setting
Phase supervision.
Table 1296: Functionality depending on Phase supervision
Value of
Phase supervision
Functionality
1 = A or AB
2 = B or BC
4 = C or CA
This selection implements single-phase voltage supervision
on the selected phase.
If the measured voltage of the supervised phase is lower
than the set value of the
Start value
setting, Level detector
enables the Timer module.
7 = A&B&C or AB&BC&CA
This selection implements three-phase voltage supervision.
The measured voltage of three supervised phases is com-
pared against the
Start value
setting.
If the number of phases where the voltage is below the
setting matches the Num of phases setting, Level detector
enables the Timer module.
Timer
Once activated, Timer runs until the value of
Operate delay time has elapsed. The
time characteristic is according to DT. When the operation timer has reached the
value of
Operate delay time, the
U_LOW
output is activated.
In a drop-off case, the remanent voltage returns to a value higher than the set value
of
Start value before Operate delay time is exceeded. Also, the timer reset state is
activated. The reset timer runs until the
Reset delay time value is exceeded. If the
duration of the voltage drop-off exceeds the set Reset delay time, the operate timer
is reset and the
U_LOW
output is deactivated.
The
BLOCK
input can be controlled with a binary input, a horizontal communication
input or an internal signal of the relay program. The activation of the
BLOCK
input
resets Timer and prevents the
U_LOW
output from being activated.
Supervision functions
1MRS759142 F
1348
REX640
Technical Manual