6-18
C70 Capacitor Bank Protection and Control System
GE Multilin
6.3 METERING
6 ACTUAL VALUES
6
h) CURRENT HARMONICS AND THD METERING
PATH: ACTUAL VALUES
METERING
SOURCE SRC 1
CURRENT HARMONICS
The metered current harmonics values are displayed in this menu. The "SRC 1" text will be replaced by whatever name
was programmed by the user 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.
i) VOLTAGE HARMONICS AND THD METERING
PATH: ACTUAL VALUES
METERING
SOURCE SRC 1
VOLTAGE HARMONICS
The metered voltage harmonics values are displayed in this menu. The “SRC 1” text will be 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 ampli-
tude 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%
MESSAGE
SRC 1
2ND Ia: 0.0
Ib: 0.0
Ic: 0.0%
MESSAGE
SRC 1
3RD Ia: 0.0
Ib: 0.0
Ic: 0.0%
↓
MESSAGE
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%
MESSAGE
SRC 1
2ND Va: 0.0
Vb: 0.0
Vc: 0.0%
MESSAGE
SRC 1
3RD Va: 0.0
Vb: 0.0
Vc: 0.0%
↓
MESSAGE
SRC 1 25TH Va: 0.0
Vb: 0.0
Vc: 0.0%
F
real
m h
,
(
)
2
N
----
f m k
–
(
)
h
ω
0
t k
( )
⋅
⋅
(
)
cos
⋅
(
)
k
=
F
imag
m h
,
(
)
2
N
----
f m k
–
(
)
h
ω
0
t k
( )
⋅
⋅
(
)
sin
⋅
(
)
k
=
F
ampl
m h
,
(
)
F
real
m h
,
(
)
2
F
imag
m h
,
(
)
2
+
=
THD
F
2
2
F
3
2
…
F
25
2
+
+
+
=
Summary of Contents for C70
Page 10: ...x C70 Capacitor Bank Protection and Control System GE Multilin TABLE OF CONTENTS ...
Page 394: ...5 270 C70 Capacitor Bank Protection and Control System GE Multilin 5 10 TESTING 5 SETTINGS 5 ...
Page 676: ...E 10 C70 Capacitor Bank Protection and Control System GE Multilin E 1 OVERVIEW APPENDIX E E ...
Page 698: ...H 8 C70 Capacitor Bank Protection and Control System GE Multilin H 3 WARRANTY APPENDIX H H ...