ABB RELION 620 Series Technical Manual page 564

Section 5
Protection-related functions
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Figure 275: Functional module diagram
Level detector
The level detector compares AI_VALUE to the Start value setting. The Operation mode
setting defines the direction of the level detector.
Table 411: Operation mode types
Operation Mode
"Under"
"Over"
The Absolute hysteresis setting can be used for preventing unnecessary oscillations if the
input signal is slightly above or below 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. If the ENA_ADD input is activated, the threshold value of the
internal comparator is the sum of the Start value Add and Start value settings. The
resulting threshold value for the comparator can be increased or decreased depending on
the sign and value of the Start value Add setting.
Timer
Once activated, the timer activates the PICKUP output. The time characteristic is
according to DT. When the operation timer has reached the value set by Operate delay
time, the TRIP output is activated. If the pickup condition disappears before the module
trips, the reset timer is activated. If the reset timer reaches the value set by Reset delay
time, the operation timer resets and the PICKUP output is deactivated.
The timer calculates the pickup duration value PICKUP_DUR, which indicates the ratio
of the pickup situation and the set trip time. The value is available in the monitored data
view.
Description
If the input signal AI_VALUE is lower than the set
value of the "Start value" setting, the level detector
enables the timer module.
If the input signal AI_VALUE exceeds the set value of
Start value setting, the level detector enables the
the
timer module.
1MAC504801-IB E
620 series ANSI
Technical Manual