ABB RER620 Technical Manual page 186

Section 4
Protection functions
180
Figure 79: Functional module diagram. I
phase sequence currents. I_A, I_B and I_C represent phase currents.
I /I
2 1
The I /I module calculates the ratio of the negative and positive phase sequence current.
2 1
It reports the calculated value to the level detector.
Level detector
The level detector compares the calculated ratio of negative and positive phase sequence
currents with the set Pickup value. If the calculated value exceeds the set Pickup value and
the min current check module has exceeded the minimum phase current limit, the level
detector activates the timer.
Min current check
The min current check module checks whether the measured phase currents are above the
set Min phase current. At least one of the phase currents needs to be above the set limit to
enable the level detector module.
Timer
Once activated, the timer activates the PICKUP output. The time characteristic is
according to DT. When the trip timer has reached the value set by Trip delay time, the
TRIP output is activated. If the fault disappears before the module trips, the reset timer is
activated. If the reset timer reaches the value set by Reset delay time, the trip timer resets
and the PICKUP output is deactivated.
The timer calculates the pickup duration (PICKUP_DUR) value which indicates the ratio
of the pickup situation and the set trip time. The value is available through 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/Blocking
mode" which selects the blocking mode. The BLOCK input can be controlled by a binary
and I represent positive and negative
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1MAC309294-MB F
RER620
Technical Manual