4.1.9.5 Operation principle
The function can be enabled and disabled with the
Operation setting
. The
corresponding parameter values are "On" and "Off".
The operation of PHPTUC can be described with a module diagram. All the modules
in the diagram are explained in the next sections.
OPERATE
Level
detector 1
BLOCK
START
Level
detector 2
OPR_A
OPR_C
OPR_B
ST_A
ST_C
ST_B
I3P
I_A
I_B
I_C
Timer
t
Figure 236: Functional module diagram
Level detector 1
This module compares the phase currents (RMS value) to the
Start value
setting.
The
Operation mode
setting can be used to select the "3-phase" or "1-phase" mode.
If in the "3-phase" mode all the phase current values are less than the value of the
Start value
setting, the 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
value of the element.
If in the "1-phase" mode any of the phase current values are less than the value of
the
Start value
setting, the condition is detected and an enable signal is sent to the
timer. This signal is disabled after all the phase currents have exceeded the set
Start
value
value of the element.
The protection relay does not accept the
Start value
to be smaller than
Current block value
.
Level detector 2
This is a low-current detection module that monitors the de-energized condition of
the protected object. The module compares the phase currents (RMS value) to the
Current block value
setting. If all the phase current values are less than the
Current
block value
setting, a signal is sent to block the operation of the timer.
Timer
Once activated, the timer activates the START output and the phase-specific ST_X
output. The time characteristic is according to DT. When the operation timer has
reached the value set by
Operate delay time
, the OPERATE output and the phase
specific OPR_X output are activated. If the fault disappears before the module
1MRS759142 F
Protection functions
REX640
Technical Manual
407
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