Application - ABB RELION REX640 Technical Manual

1MRS759142 C
6.8.6
REX640
Technical Manual
Table 1179: Functionality depending on Phase supervision
Phase supervision
Value of
1 = A or AB
2 = B or BC
4 = C or CA
7 = A&B&C or AB&BC&CA
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.

Application

Systems with critical motor applications provide a backup power source that can be
switched in when the primary power source becomes faulty. When the power to a
motor is suddenly lost, the motor terminal voltage does not immediately fall to zero
because the rotating motor now acts as a generator producing its own voltage.
Remanent voltage decays as the motor comes to a stop at a rate depending on the motor
and load. Connecting the backup power source while the remanent voltage is at a high
level can result in damage to the motor shaft and windings.
MSVPR is used to monitor the motor remanent voltage over a decaying frequency
after power supply is lost, before allowing connection of backup power. It provides a
permissive signal indicating when the backup power can be safely connected.
This application example describes the re-energization process. MSVPR is used to
supervise the Bus1 remanent voltage. Control logic is used to detect the loss of
primary power source and initiate the transfer to backup power. Normally, bus tie
breaker CB5 is open and motor voltage power is supplied by incoming Feeder1 (see
Figure 677).
Functionality
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.
This selection implements three-phase voltage supervision. The
measured voltage of three supervised phases is compared against the
Start value setting.
If the number of phases where the voltage is below the setting matches
Num of phases setting, Level detector enables the Timer module.
the
Section 6
Supervision functions
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