CHAPTER 6: ACTUAL VALUES
METERING
F35 MULTIPLE FEEDER PROTECTION SYSTEM – INSTRUCTION MANUAL
6-21
6
6.4.2.10 Current harmonics and THD metering
ACTUAL VALUES
METERING
SOURCE SRC 1
CURRENT HARMONICS
This menu displays metered current harmonics values. The "SRC 1" text is replaced by the name was programmed for the
associated source (see
SETTINGS
SYSTEM SETUP
SIGNAL SOURCES
). Current harmonics are measured for each source
for the total harmonic distortion (THD) and 2nd to 25th harmonics per phase.
6.4.2.11 Voltage harmonics and THD metering
ACTUAL VALUES
METERING
SOURCE SRC 1
VOLTAGE HARMONICS
This menu displays metered voltage harmonics values. The “SRC 1” text is replaced by the programmed name for the
associated source (see the
SETTINGS
SYSTEM SETUP
SIGNAL SOURCES
menu).
To extract the 2nd to 25th voltage harmonics, each harmonic is computed on a per-phase basis, where:
N = 64 is the number of samples per cycle
ω
0
= 2
π
f is the angular frequency based on the system frequency (50 or 60 Hz)
k = 1, 2,..., N – 1 is the index over one cycle for the Fast Fourier Transform (FFT)
m is the last sample number for the sliding window
h = 1, 2,..., 25 is the harmonic number
The short-time Fourier transform is applied to the unfiltered signal:
Eq. 6-3
The harmonics are a percentage of the fundamental signal obtained as a ratio of harmonic amplitude to fundamental
amplitude multiplied by 100%. The total harmonic distortion (THD) is the ratio of the total harmonic content to the
fundamental:
Eq. 6-4
CURRENT HARMONICS
SRC 1
SRC 1 THD Ia: 0.0
Ib: 0.0 Ic: 0.0%
SRC 1 2ND Ia: 0.0
Ib: 0.0 Ic: 0.0%
SRC 1 3RD Ia: 0.0
Ib: 0.0 Ic: 0.0%
SRC 1 25TH Ia: 0.0
Ib: 0.0 Ic: 0.0%
VOLTAGE HARMONICS
SRC 1
SRC 1 THD Va: 0.0
Vb: 0.0 Vc: 0.0%
SRC 1 2ND Va: 0.0
Vb: 0.0 Vc: 0.0%
SRC 1 3RD Va: 0.0
Vb: 0.0 Vc: 0.0%
SRC 1 25TH Va: 0.0
Vb: 0.0 Vc: 0.0%