Figure 234: Functional module diagram
I_2H/I_1H
This module calculates the ratio of the second harmonic (I_2H) and fundamental
frequency (I_1H) phase currents. The calculated value is compared to the set
Start
value
. If the calculated value exceeds the set
Start value
, the module output is
activated.
Level detector
The output of the phase specific level detector is activated when the fundamental
frequency current I_1H exceeds five percent of the nominal current.
Timer
Once activated, the timer runs until the set
Operate delay time
value. The time
characteristic is according to DT. When the operation timer has reached the
Operate
delay time
value, the BLK2H output is activated. After the timer has elapsed and the
inrush situation still exists, the BLK2H signal remains active until the I_2H/I_1H ratio
drops below the value set for the ratio in all phases, that is, until the 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
Reset delay time
, 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.
It is recommended to use the second harmonic and the waveform based
inrush blocking from the TR2PTDF function, if available.
1MRS758755 C Protection related functions
REC615 & RER615
Technical Manual
477
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