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6.3 METERING
j) VOLTAGE HARMONICS AND THD METERING
PATH: ACTUAL VALUES
VOLTAGE HARMONICS
SRC 1
The metered current harmonics values are displayed in this menu. The "SRC 1" text will be replaced by the programmed
name for the associated source (see the
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
= 2πf is the angular frequency based on the system frequency (50 or 60 Hz)
0
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:
6
The harmonics are a percentage of the fundamental signal obtained as a ratio of harmonic amplitude to fundamental ampli-
tude multiplied by 100%. The total harmonic distortion (THD) is the ratio of the total harmonic content to the fundamental:
Voltage harmonics are calculated only for Wye connected phase VTs. Ensure the
VOLTAGE BANK F5
NOTE
PATH: ACTUAL VALUES
TRACKING FREQUENCY
The tracking frequency is displayed here. The frequency is tracked based on the selection of the reference source with the
FREQUENCY AND PHASE REFERENCE
Power System section of chapter 5 for additional details.
6-18
METERING
SOURCE SRC 1
SRC 1
THD Va:
Vb:
0.0 Vc:
SRC 1
2ND Va:
MESSAGE
Vb:
0.0 Vc:
SRC 1
3RD Va:
MESSAGE
Vb:
0.0 Vc:
SRC 1
25TH Va:
MESSAGE
Vb:
0.0 Vc:
SETTINGS
2
∑
(
,
)
--- -
F
m h
=
real
N
k
2
∑
(
m h ,
)
--- -
F
=
imag
N
k
(
m h ,
)
F
F
=
ampl
real
THD
=
PHASE VT XX CONNECTION
METERING
TRACKING FREQUENCY
TRACKING FREQUENCY:
60.00 Hz
setting in the
SETTINGS
F35 Multiple Feeder Protection System
VOLTAGE HARMONICS
0.0
0.0%
0.0
0.0%
0.0
0.0%
↓
0.0
0.0%
SYSTEM SETUP
SIGNAL SOURCES
(
(
)
⋅
(
h ω
⋅
⋅
t k ( )
)
)
f m k
–
cos
0
(
(
)
⋅
(
h ω
⋅
⋅
t k ( )
)
)
f m k
–
sin
0
2
2
(
,
)
(
,
)
m h
F
m h
+
imag
2
2
2
...
F
+
F
+
+
F
2
3
25
setting is "Wye" to enable voltage harmonics metering.
SYSTEM SETUP
6 ACTUAL VALUES
menu).
(EQ 6.1)
(EQ 6.2)
SYSTEM SETUP
AC INPUTS
6.3.3 TRACKING FREQUENCY
menu. Refer to the
POWER SYSTEM
GE Multilin
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