ABB RELION 620 Series Technical Manual page 673

1MRS757644 F
620 series
Technical Manual
GUID-F1E58B1E-03CB-4A3C-BD1B-F809420397ED V1 EN
Figure 338: 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.
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 function. The operation modes are
controlled by the BLOCK input and the global setting in Configuration/System/
Blocking mode which selects the blocking mode. The BLOCK input can be controlled
by a binary input, a horizontal communication input or an internal signal of the
protection relay's program. The influence of the BLOCK signal activation is
preselected with the global setting Blocking mode.
The Blocking mode setting has three blocking methods. In the "Freeze timers" mode,
the operation timer is frozen to the prevailing value, but the OPERATE output is not
deactivated when blocking is activated. In the "Block all" mode, the whole function is
blocked and the timers are reset. In the "Block OPERATE output" mode, the function
operates normally but the OPERATE output is not activated.
Protection functions
is used for representing positive
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Section 4
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