ABB RELION REX640 Technical Manual page 1159

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elapsed and the inrush situation still exists, the Timer module output remains
active until the I_2H/I_1H ratio drops below the set
inrush situation is over. If the drop-off situation occurs within the operate time up
counting, the reset timer is activated. If the drop-off time exceeds
the operate timer is reset.
The BLOCK input can be controlled with a binary input, a horizontal communication
input or an internal signal of the relay program. The activation of the BLOCK input
prevents the BLK2H output from being activated.
Phase selection logic
This module determines the number of phases used for activating the BLK2H
output. If Num of start phases = "1 out of 3", an inrush on any of the phases
activates output BLK2H. If the set value equals "2 out of 3", an inrush or at least two
phases are required to activate output BLK2H.
5.1.6 Application
Transformer protections require high stability to avoid tripping during magnetizing
inrush conditions. A typical example of an inrush detector application is doubling
the start value of an overcurrent protection during inrush detection.
The inrush detection function can be used to selectively block overcurrent and
earth-fault function stages when the ratio of the second harmonic component to
the fundamental component exceeds the set value.
Other applications of this function include the detection of inrush in lines
connected to a transformer.
REX640
Technical Manual
Protection related functions
Start value , that is, until the
Reset delay time ,
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