ABB REF615 F - Operation Principle

The function contains a blocking functionality. It is possible to block function
outputs, the definite timer or the function itself, if desired.
4.5.5.4 Operation principle
The function can be enabled and disabled with the Operation setting. The
corresponding parameter values are "On" and "Off".
The operation of the positive-sequence undervoltage protection can be described
using a module diagram. All the modules in the diagram are explained in the next
sections.
GUID-F1E58B1E-03CB-4A3C-BD1B-F809420397ED V1 EN
Figure 259: Functional module diagram. U
1
is used for representing positive
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.
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.
The timer calculates the start duration value START_DUR, which indicates the
percentage ratio of the start situation and the set operation time. The value is
available in the monitored data view.
Blocking logic
There are three operation modes in the blocking functionality. The operation modes
are controlled by the BLOCK input and the global setting "Configuration/System/
Section 4 1YHT530004D05 D
Protection functions
490 615 series
Technical Manual