GE UR F35 Series Instruction Manual page 361

6 ACTUAL VALUES
i) FREQUENCY METERING

PATH: ACTUAL VALUES METERING
 FREQUENCY
 SRC 1
The metered frequency values are displayed in this menu. The "SRC 1" text will be replaced by whatever name was pro-
grammed by the user for the associated source (see
is measured via software-implemented zero-crossing detection of an AC signal. The signal is either a
SOURCE FREQUENCY
Clarke transformation of three-phase voltages or currents, auxiliary voltage, or ground current as per source configuration
(see the 
SYSTEM SETUP
final frequency measurement is passed through a validation filter that eliminates false readings due to signal distortions and
transients.
j) VOLTAGE HARMONICS AND THD METERING

PATH: ACTUAL VALUES METERING
 VOLTAGE HARMONICS
 SRC 1
MESSAGE
MESSAGE
MESSAGE
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
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:
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
GE Multilin
 
SOURCE SRC 1
SRC 1 FREQUENCY:
0.00 Hz
SETTINGS
settings). The signal used for frequency estimation is low-pass filtered. The
POWER SYSTEM
 
SOURCE SRC 1
SRC 1 THD Va:
Vb: 0.0 Vc:
SRC 1 2ND Va:
Vb: 0.0 Vc:
SRC 1 3RD Va:
Vb: 0.0 Vc:
↓
SRC 1 25TH Va:
Vb: 0.0 Vc:

SETTINGS SYSTEM SETUP
2

F ( m h , ) --- - ( f m k (
= –
real
N
k
2

F ( m h , ) --- - ( f m k (
=
imag
N
k
( m h , ) ( ,
F F m h
=
ampl real
2
THD F F
= +
2
setting is "Wye" to enable voltage harmonics metering.
PHASE VT XX CONNECTION
F35 Multiple Feeder Protection System
FREQUENCY
 
SYSTEM SETUP SIGNAL SOURCES
VOLTAGE HARMONICS
0.0
0.0%
0.0
0.0%
0.0
0.0%
0.0
0.0%

SIGNAL SOURCES
) ⋅ cos ( h ω ⋅ ⋅ t k ( ) ) )
0
) ⋅ sin ( h ω ⋅ ⋅ t k ( ) ) )
–
0
2 2
) ( , )
F m h
+
imag
2 2
... F
+ +
3 25
6.3 METERING
).
menu).
(EQ 6.3)
(EQ 6.4)
 
SYSTEM SETUP AC INPUTS
6-21
6