5.1.4
Operation principle
The function can be enabled and disabled with the
Operation
setting. The corresponding
parameter values are “Enable” and “Disable”.
The operation of INR can be described using a module diagram. All the modules in the
diagram are explained in the next sections.
A070694 V2 EN
Figure 152:
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
Pickup
value
. If the calculated value exceeds the set
Pickup 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
Trip delay time
value. The time characteristic
is according to DT. When the operation timer has reached the
Trip 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
Section 5
1MRS240050-IB C
Protection-related functions
314
REF615R
Technical Manual
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