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Figure. 5.6.5. - 155. Simpli ed function block diagram of the THD function.
Measured input values
Function block uses analog current measurement values. Function block always utilizes FFT
measurement of whole harmonic specter of 32 components from each measured current channel
which from the THD is calculated either as amplitude or power ratio THD. -20ms averaged value of the
selected magnitude is used for pre-fault data registering.
Table. 5.6.5. - 129. Analogic magnitudes used by the THD function.
Signal
Description
Time base
IL1FFT
Fundamental RMS measurement of phase L1/A current
5 ms
IL2FFT
Fundamental RMS measurement of phase L2/B current
5 ms
IL3FFT
Fundamental RMS measurement of phase L3/C current
5 ms
I01FFT
Fundamental RMS measurement of residual I01 current
5 ms
I02FFT
Fundamental RMS measurement of residual I02 current
5 ms
Selection of the THD calculation method is made with a setting parameter commonly for all of the
measurement channels.
General settings
The following general settings de ne the general behavior of the function. These settings are static i.e.
it is not possible change them with setting group switching.
Table. 5.6.5. - 130. General settings of the function
Name
Description
Range
Step
Default
Measurement
magnitude
De nes which available measured magnitude of THD is used by
the function.
1:Amplitude
2:Powers
-
1:Amplitude
THD in side
De nes which current measurement module is used by the
function.
1:Side1
2:Side2
-
1:Side1
AQ-T216
Instruction manual
Version: 2.00
225
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