7-3
IM WT3001E-51EN
Harmonic Measurement in Normal Measurement Mode (Option)
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Index
Likewise, the computing method of active power P, apparent power S, reactive power Q,
power factor λ, and phase angle φ also varies by measurement mode, and the frequency
components that are included differ.
• Elements
Element refers to a set of input terminals that can input a single phase of voltage
and current to be measured. This instrument can contain up to four elements, which
are numbered from 1 to 4. An element number is appended to the measurement
function symbol for the measured data that this instrument displays, so that the
correspondence between the numeric data and the element can be seen. For
example, “U1(2)” represents the voltage of the 2
nd
order harmonic of element 1.
• Wiring System
You can specify five wiring systems—single-phase, two-wire; single-phase, three-wire;
three-phase, three-wire; three-phase, four-wire; and three-phase, three-wire (three-
voltage, three current)—on this instrument to measure the power of various single-
phase and three-phase power transmission systems.
• Wiring Unit
A wiring unit refers to a set of two or three input elements of the same wiring system
that are grouped. Depending on the wiring system pattern, up to two wiring units can
be constructed, which are represented by symbols ΣA and ΣB. The measurement
function of a wiring unit is called a Σ function.
For example, “UΣA(1)” represents the voltage average of the fundamental signal of
the input elements that are assigned to wiring unit ΣA.
• PLL Source «For procedures, see section 7.4»
When measuring harmonics, the fundamental period (period of the fundamental
signal) must be determined in order to analyze the higher orders. The PLL (Phase
Locked Loop) source is the signal that is used to determine the fundamental period.
Selecting a signal with little distortion or fluctuation for the PLL source results in a
stable harmonic measurement. An ideal signal would be a rectangular wave with
amplitude that is greater than or equal to 50% or 100% of the measurement range (see
section 1.3) when the crest factor (see section 4.6 in the
User’s Manual IM WT3001E-
01EN
) is set to 3 or 6, respectively.
In addition, stable harmonic measurement can also be achieved by applying a clock
signal (Ext Clk) that has the same period as the waveform on which to perform
harmonic measurements.
For a description of the terminology such as fundamental signal, harmonic signal, and
harmonic order, see appendix 4 in the
User’s Manual IM WT3001E-01EN
.
7.1 Harmonic Measurement Function
