hager hw+ User Manual

92 6LE008146B
Measurement functions
6.8 Measurement of total harmonic distortion THD
The sentinel Energy trip unit calculates the rate of harmonic distortion (Total Harmonic
Distortion) every second based on real-time measurements of current and voltage.
The availability of these measurements depends on the type of rating plug installed.
These calculations are carried out up to harmonics of the 31st order with accuracy class 2 in
accordance with IEC 61557-12.
The harmonic distortion rates are energy distribution quality indicators. The THDi is used to
determine the current wave deformation rate. The THDU or THDV is used to determine the
voltage wave deformation rate.
Harmonic distortion THD in current THDi
The current THD is the percentage of the RMS value of current harmonics of a rank above
one, compared to the RMS value of the harmonic current of rank one.
As the rate is calculated in relation to the fundamental, its value can exceed 100%.
The THDi or, in other words, deformation rate of the current wave is caused by receiver
non-linearity, which produces non-sinusoidal current waveforms. Therefore the THDi enables
potential polluter receivers in energy distribution to be identified.
A THDi < 10% shows low pollution which is generally acceptable.
A THDi up to 50% indicates risky levels of pollution (risk of overheating, etc.).
A THDi above 50% is a high harmonics percentage and may result in serious degradation,
dangerous overheating and risk of malfunctions if the installation has not been designed
correctly.
Total harmonic distortion of voltage THD, THDU, THDV
The THD of voltage is the percentage of the RMS value of harmonic voltages of a rank above
one, compared to the RMS value of the harmonic voltage of rank one.
Its value can theoretically exceed 100% but, in practice, it does not exceed 25%.
The THD of voltage is used to assess the impact of the impedance of the line on the quality
of the voltage at the level of the pollutant receivers. The higher the impedance of the lines
supplying these receivers, the higher the THD of voltage.
The exhaustive list of variables calculated according to the 3-pole or 4-pole version is given in
the following table:
Calculation formula symbol Definition
Rank n root-mean-square harmonic component for the
current of pole p
Calculation formula symbol Definition
Harmonic RMS component of rank n for voltage with pg =
12, 23, 31
Electrical variable Symbol 3-pole
version
4-pole
version
Neutral current THD THD IN
■ ■
Phase current THD THD I1, THD I2, THD I3
■ ■
THD of single voltages THD V1N, THD V2N, THD V3N
-
■
THD of compound voltages THD U12, THD U23, THD U31
■ ■

hager hw+ Specifications

General

Brand	hager
Model	hw+
Category	Circuit breakers
Language	English