User manual
5 Power quality - a guide
79
Fig. 31. The effect of 9th harmonic interaction (450 Hz, 10% Unom) and interharmonic
460 Hz (10% Unom). The apparent change in the voltage envelope with frequency of 10Hz
that may cause flicker (Unom = 230 V RMS, 50 Hz).
5.5.1 Total Interharmonic Distortion
A measure of the total presence of interharmonics is the TID, which is defined as:
where: TID
F
- Total Interharmonic Distortion related to fundamental component,
TID
R
- Total Interharmonic Distortion related to RMS value,
A
ih
– RMS of ih-th interharmonic (interharmonic sub-group),
A
1
– RMS of the fundamental component,
A
RMS
– RMS of the waveform,
n - in case of PQM-702 and PQM-703 it is equal to 50.
TID is the ratio of the RMS value of all interharmonics to the fundamental component (for TID
F
) or
RMS value (for TID
R
).
Acceptable level of interharmonic interferences in voltage is a matter discussed among profes-
sionals involved power quality matters. Some sources state that the overall rate of voltage interhar-
monics distortion should not exceed 0.2%.
5.6 Mains signalling
Ripple control signals are signals entered into the electricity network in order to control and
check of remote control devices connected to the same network. In addition to the transmission of
electricity, a distribution network is in this case used as a transmission medium for communication
between devices. EN 50160 standard distinguishes three types of signals:
Ripple control signals from 110 to 3000 Hz,
Power Line Carrier Communication, PLCC, frequency range from 3 to 148.5 kHz,
Marking signals, short transients imposed at a specific point on the voltage waveform.
-400
-300
-200
-100
0
100
200
300
400