GE UR Series C70, Instruction Manual

Page: 360 / 614

6-16 C70 Capacitor Bank Protection and Control System GE Multilin
6.3 METERING 6 ACTUAL VALUES
6
i) 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
= 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 6.1)
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 CAPACITOR CONTROL
PATH: ACTUAL VALUES
ÖØ
METERING
ÖØ
CAPACITOR CONTROL
These values indicate the time remaining before the next permissible close operation for each of the four capacitor banks.
„
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%
„
CAPACITOR CONTROL
„
CAP 1 DISCHARGE TIME:
0 s
MESSAGE
CAP 2 DISCHARGE TIME:
0 s
MESSAGE
CAP 3 DISCHARGE TIME:
0 s
MESSAGE
CAP 4 DISCHARGE TIME:
0 s
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
+ + + =
NOTE