ABB RELION REX640, Техническое руководство, Страница: 403 / 1960

blocks in this document. The configuration can be written to the protection relay
once the mismatch is corrected.
4.1.8.5 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of LOFLPTUC can be described using a module diagram. All the
modules in the diagram are explained in the next sections.
Level
detector 1
Level
detector 2
t
Timer
OPERATE
START
BLOCK
I_A
I_B
I_C
I3P
Figure 234: Functional module diagram
Level detector 1
This module compares the phase currents (RMS value) to the set
Start value high
setting. If all the phase current values are less than the set
Start value high value,
the loss of load condition is detected and an enable signal is sent to the timer. This
signal is disabled after one or several phase currents have exceeded the set
Start
value high value of the element.
Level detector 2
This is a low-current detection module, which monitors the de-energized condition
of the motor. It compares the phase currents (RMS value) to the set Start value low
setting. If any of the phase current values is less than the set Start value low, a
signal is sent to block the operation of the timer.
Timer
Once activated, the timer activates the
START
output. The time characteristic is
according to DT. When the operation timer has reached the value set by Operate
delay time, the
OPERATE
output is activated. If the fault disappears before the
module operates, the reset timer is activated. If the reset timer reaches the
value set by
Reset delay time, the operate timer resets and the
START
output is
deactivated.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operating time. The value is
available in the monitored data view.
The
BLOCK
signal blocks the operation of the function and resets the timer.
1MRS759142 F Protection functions
REX640
Technical Manual
403