Application Guide - NP900 Series
494 (504
)
A996A
Figure 3.7.6-234 Simplified function block diagram of the THD function.
3.7.6.1
M
EASURED 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 3.7.6.1-289 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.
3.7.6.2
P
ICK
-
UP CHARACTERISTICS
Pick-up and activation of the THD function alarm is controlled by
IsetPh, IsetI01 and
IsetI02
pick-up setting parameters, which defines the maximum allowed measured current
THD before action from the function. In order to have alarm signals activated from the
function, the corresponding pick-up element needs to be activated by the
Enable PH
,
Enable I01
and
Enable I02
setting parameters. Each pick-up element can be activated
individually. The function constantly calculates the ratio in between of the setting values
and measured magnitude (Im) per all three phases. Reset ratio of 97 % is inbuilt in the
Содержание NP900 Series
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Страница 49: ...Application Guide NP900 Series 49 504 A996A Figure 3 2 1 3 25 Definite time operating characteristics...
Страница 50: ...Application Guide NP900 Series 50 504 A996A Figure 3 2 1 3 26 IEC predefined characteristics NI VI LTI and EI...
Страница 52: ...Application Guide NP900 Series 52 504 A996A Figure 3 2 1 3 28 IEEE predefined characteristics EI MI and VI...
Страница 243: ...Application Guide NP900 Series 243 504 A996A Figure 3 3 2 1 122 NPS biased thermal trip curves with kNPS values 7 and 10...
Страница 491: ...Application Guide NP900 Series 491 504 A996A 3 7 5 6 SETTING EXAMPLE...
Страница 504: ...Application Guide NP900 Series 504 504 A996A A996A...