hager h3+ - Measuring Power Factors

536LE005550A
Function of the Energy trip unit
3.3 Measurement function
Total harmonic distortion of voltage THD, THDU, THDV
The THD of voltage is the percentage of the root-mean-square value of harmonic
voltages of a rank above one, compared to the root-mean-square value of the
harmonic voltage of rank one.
Its value can theoretically exceed 100% but, in practice, it does not exceed 25%.
Calculation formula symbol Definition
Harmonic RMS component of rank n for voltage
with pg = 12, 23, 31
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 version 3P or 4P is given in
the following table:
Electrical variable Symbol
Version
3 P
Version
4 P
Phase current THD THD I1, THD I2, THD I3
X X
THD of voltage Ph-N THD V1N, THD V2N, THD V3N
– X
THD of voltage Ph-Ph HD U12, THD U23, THD U31
X X
3.3.9
Measuring power factors
The Energy trip unit calculates in real-time (every second) the power factor (PFtot)
from the ratio of total active power to total apparent power. It also calculates the
power factors per phase from the ratios of total active power per phase to apparent
power per phase.
Example: Formula for the power factor per phase.
Calculation formula symbol Definition
Phase number.
The Energy trip unit also calculates in real-time (every second) the total cos φ from
the ratio of total active power reduced to the harmonics of rank 1 to total apparent
power reduced to the harmonics of rank 1. In addition, it calculates the cos φ per
phase.