GE Multilin F35 - Tracking Frequency

6-18 F35 Multiple Feeder Protection System GE Multilin
6.3 METERING 6 ACTUAL VALUES
6
j) VOLTAGE HARMONICS AND THD METERING
PATH: ACTUAL VALUES ÖØ METERING Ö SOURCE SRC 1 ÖØ VOLTAGE HARMONICS
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
SETTINGS ÖØ SYSTEM SETUP ÖØ 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
= 2πf 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 6.1)
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 6.2)
Voltage harmonics are calculated only for Wye connected phase VTs. Ensure the SYSTEM SETUP Ö AC INPUTS ÖØ
VOLTAGE BANK F5 ÖØ PHASE VT XX CONNECTION setting is “Wye” to enable voltage harmonics metering.
6.3.3 TRACKING FREQUENCY
PATH: ACTUAL VALUES ÖØ METERING ÖØ 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 setting in the SETTINGS ÖØ SYSTEM SETUP ÖØ POWER SYSTEM menu. Refer to the
Power System section of chapter 5 for additional details.
 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%
 TRACKING FREQUENCY

TRACKING FREQUENCY:
60.00 Hz
F
real
mh,()
2
N
----
fm k–() h ω
0
tk()⋅⋅()cos⋅()
k
∑
=
F
imag
mh,()
2
N
----
fm k–()h ω
0
tk()⋅⋅()sin⋅()
k
∑
=
F
ampl
mh,() F
real
mh,()
2
F
imag
mh,()
2
+=
THD F
2
2
F
3
2
… F
25
2
+++=
NOTE