Operation Principle - ABB RELION REX640 Technical Manual

1MRS759142 C
4.5.6.5
REX640
Technical Manual
troubleshooting, check the contents of this chapter and also the preprocessing blocks
in this document. The configuration can be written to the protection relay once the
mismatch is corrected.

Operation principle

The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "on" and "off".
The operation of PSPTUV can be described using a module diagram. All the modules
in the diagram are explained in the next sections.
U
U3P
1
BLOCK
GUID-76CB5783-01B0-436D-90E0-D2D787A05955 V1 EN
Figure 434: Functional module diagram. U
phase sequence voltage.
Level detector
The calculated positive-sequence voltage is compared to the set Start value setting. If
the value drops below the set Start value, the level detector enables the timer. The
Relative hysteresis setting can be used for preventing unnecessary oscillations if the
input signal slightly varies from the Start value setting. After leaving the hysteresis
area, the start condition has to be fulfilled again and it is not sufficient for the signal
to only return to the hysteresis area.
The level detector contains a low-level blocking functionality for cases where the
positive-sequence voltage is below the desired level. This feature is useful when
unnecessary starts and operates are wanted to avoid during, for example, an
autoreclose sequence. The low-level blocking is activated by default (Enable block
value is set to "Enabled") and the blocking level can be set with the Voltage block
value setting.
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 undervoltage condition persists. If the
positive-sequence voltage normalizes 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.
Timer
Level
t
detector
Blocking
logic
1
Section 4
Protection functions
OPERATE
START
is used for representing positive
797