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364
KHA3000
A
Basic Terms and Definitions
This appendix explains the main terms concerning harmonics, flicker and voltage fluctuations
used in this manual. For details of each term, refer to the corresponding standards.
Basic terms related to the harmonic test
Basic terms related to the voltage fluctuation and flicker tests
THC Total harmonic current: the sum of effective values of harmonic current components
from the 2nd to 40th order
POHC Partial odd-order harmonic current: the sum of effective values of partial odd-order
harmonic current components from the 21st to 39th order
THD Total harmonic distortion: effective value ratio of harmonic components from the 2nd
to 40th order to the effective value of the fundamental components
PWHD Partial-weighted harmonic distortion: effective value ratio of harmonic components
from the 14th to 40th order to the effective value of the fundamental components
Reference current The average rms current during the test period.
Reference fundamental current Effective values of fundamental components of rated line current of equipment
Ssc Short-circuit power (three-phase short-circuit power) determined by nominal line
voltage and system impedance (value of power supply frequency) at common
connection point
Rsce Short-circuit ratio: Ratio of rated apparent power of equipment to short-circuit power
Single-phase equipment: Rsce = Ssc / (3
× Rated apparent power of single-phase
equipment)
Line equipment: Rsce = Ssc / (2 × Rated apparent power of line equipment)
Three-phase equipment: Rsce = Ssc / (1 × Rated apparent power of all three-phase
equipment)
Observation period (Tobs) Observation period of the test: The operation type of the EUT determines the
necessary observation period. The operation types refer to the types of changes in
harmonic current and include the following four types: quasi-stationary, short cyclic,
random and long cyclic.
Hybrid equipment Equipment using composite load. A balanced three-phase load is combined with one
or more loads of other circuits. A load of another circuit means a load between a
phase and a neutral line or a load between lines.
Pst Auto
Performs d measurement (dmax, Tmax (d(t)>3.3%) and dc) and Pst and Plt (flicker)
measurement simultaneously. The results of d measurement are displayed in the
form of the maximum value at each Pst measurement segment time.
Manual Executes measurement with a method that conforms to “ Test conditions and
procedures for measuring voltage changes caused by manual switching. ” This product
makes judgment based on the arithmetic average of 22 measured values obtained by
excluding the maximum and minimum values of 24 collected measurements.
Pst Short-time flicker value of one segment (Seg1 and subsequent segment) time
Plt Long-time flicker value in all segment (Seg1 and subsequent segments) times (set
with the Pst measurement count)
dc, dc maximum value Maximum value of relative steady voltage changes in one segment (Seg1 and
subsequent segment) time
dmax, dmax maximum value Maximum value of maximum relative voltage changes in one segment (Seg1 and
subsequent segment) time
Tmax (d(t)>3.3%),
Tmax (d(t)>3.3%) maximum value Maximum value of time during which d(t) exceeds 3.3 % in one segment (Seg1 and
subsequent segment) time
Zsys1-3[ohm] Permissible system impedance value calculated after converting the measured
values of dmax, dc and Plt with a set impedance