GE L90 Instruction Manual page 618

METERING
If the 87L function is enabled, then dedicated 87L frequency tracking is engaged. In this case, the relay uses the
 TRACKING FREQUENCY  TRACKING FREQUENCY
6.4.3.10 Current harmonics and THD metering
ACTUAL VALUES  METERING  SOURCE SRC 1  CURRENT HARMONICS
 CURRENT HARMONICS
 SRC 1
This menu displays metered current harmonics values. The "SRC 1" text is replaced by the name was programmed for the
associated source (see
for the total harmonic distortion (THD) and 2nd to 25th harmonics per phase.
6.4.3.11 Voltage harmonics and THD metering
ACTUAL VALUES  METERING  SOURCE SRC 1  VOLTAGE HARMONICS
 VOLTAGE HARMONICS
 SRC 1
6
This menu displays metered voltage harmonics values. The "SRC 1" text is 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:
6-22
value for all computations, overriding the
SRC 1 THD Ia: 0.0

Ib: 0.0 Ic: 0.0%
SRC 1 2ND Ia: 0.0

Ib: 0.0 Ic: 0.0%
SRC 1 3RD Ia: 0.0

Ib: 0.0 Ic: 0.0%
SRC 1 25TH Ia: 0.0

Ib: 0.0 Ic: 0.0%
SETTINGS  SYSTEM SETUP  SIGNAL SOURCES
SRC 1 THD Va: 0.0

Vb: 0.0 Vc: 0.0%
SRC 1 2ND Va: 0.0

Vb: 0.0 Vc: 0.0%
SRC 1 3RD Va: 0.0

Vb: 0.0 Vc: 0.0%
SRC 1 25TH Va: 0.0

Vb: 0.0 Vc: 0.0%
SETTINGS  SYSTEM SETUP  SIGNAL SOURCES

). Current harmonics are measured for each source

menu).
L90 LINE CURRENT DIFFERENTIAL SYSTEM – INSTRUCTION MANUAL
CHAPTER 6: ACTUAL VALUES
METERING
value.
SOURCE FREQUENCY
Eq. 6-3