Capacitor Control - GE C70 Instruction Manual

6.3 METERING
i) 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

= 2f 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
 CAPACITOR CONTROL

These values indicate the time remaining before the next permissible close operation for each of the four capacitor banks.
6-18
 
METERING SOURCE SRC 1
SRC 1
Vb: 0.0 Vc:
SRC 1
MESSAGE
Vb: 0.0 Vc:
SRC 1
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
THD
=

PHASE VT XX CONNECTION
 
METERING

CAPACITOR CONTROL

CAP 1 DISCHARGE TIME:
0 s
CAP 2 DISCHARGE TIME:
MESSAGE
0 s
CAP 3 DISCHARGE TIME:
MESSAGE
0 s
CAP 4 DISCHARGE TIME:
MESSAGE
0 s
C70 Capacitor Bank Protection and Control System

VOLTAGE HARMONICS
THD Va: 0.0
0.0%
2ND Va: 0.0
0.0%
3RD Va: 0.0
0.0%

0.0
0.0%

SYSTEM SETUP SIGNAL SOURCES
     h    t k    
f m k cos
–
0
     h    t k    
f m k sin
–
0
2 2
     
m h F m h
+
real imag
2 2 2

F F F
+ + +
2 3 25
setting is "Wye" to enable voltage harmonics metering.
6 ACTUAL VALUES
menu).
(EQ 6.1)
(EQ 6.2)
 
SYSTEM SETUP AC INPUTS
6.3.3 CAPACITOR CONTROL
GE Multilin