Figure. 5.4.5. - 38. Simpli ed function block diagram of the DEF function.
Measured input value
Function block uses analog current measurement values. Function block always utilizes peak-to-peak
measurement from samples and by user selection the monitored magnitude can be either fundamental
frequency RMS values, True RMS values from the whole harmonic specter of 32 components or peak
to peak values. -20ms averaged value of the selected magnitude is used for pre-fault data registering.
Fault current angle is based on comparing neutral voltage U0 angle. Both I0 and U0 must be above
squelch limit to be able to detect the angle. Squelch limit for I0 current is 0.01 x In and for voltage 0.01
x Un.
Table. 5.4.5. - 75. Analogic magnitudes used by the DEF function.
Signal
Description
Time base
I01PP
Peak-to-peak measurement of coarse residual current measurement input I01
5 ms
I01RMS
Fundamental RMS measurement of coarse residual current measurement input I01
5 ms
I01TRMS TRMS measurement of coarse residual current measurement input I01
5 ms
I02PP
Peak-to-peak measurement of sensitive residual current measurement input I02
5 ms
I02RMS
Fundamental RMS measurement of sensitive residual current measurement input I02
5 ms
I02TRMS TRMS measurement of coarse sensitive current measurement input I02
5 ms
I0Calc
Fundamental RMS value of the calculated residual current from the three phase currents
5 ms
U0RMS
Fundamental RMS measurement of zero sequence voltage measurement input U0
5 ms
U0Calc
Fundamental RMS value of the calculated zero sequence voltage from the three phase voltages
5 ms
Selection of the used AI channel is made with a setting parameter. In all possible input channel
variations pre-fault condition is presented with 20 ms averaged history value from -20 ms of Start or
Trip event.
AQ-F255
Instruction manual
Version: 2.00
75
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