A7
Appendix
IEC61000-4-7
An international standard governing measurement of harmonic cur-
rent and harmonic voltage in power supply systems as well as har-
monic current emitted by equipment. The standard specifies the
performance of a standard instrument.
LAN
LAN is the abbreviation of Local Area Network. The LAN was devel-
oped as a network for transferring data through a PC within a local
area, such a
s an office, factory, or school.
This device comes equipped with the LAN adapter Ethernet 10/
100Base-
T
.Use a twisted-pair cable to connect this device to the
hub (central computer) of your LAN. The maximum length of the
cable connecting the terminal and the hub is 100 m. Communica-
tions using TCP/IP as the LAN interface protocol are supported.
Power factor (PF/
DPF)
Power factor is the ratio of effective power to apparent power. The
larger
the absolute value of the power factor, the greater the propor-
tion of effective power, which provides the power that is consumed,
and th
e gr
eater the efficiency. The maximum absolute value is 1.
Conversely, the smaller the absolute value of the power factor, the
greater the proportion of reactive power, which is not consumed,
and the lower the efficiency. The minimum absolute value is 0.
A positive value (LAG) indicates that the current phase is lagging
the volt
a
ge. Inductive loads (such as motors) are characterized by
lagging phase. A negative value (LEAD) indicates that the current
phase is leading the voltage. Capacitive loads (such as capacitors)
are characterized by leading phase. Sign is reversed harmonic
phase angle, and the phase difference.
The power factor (PF) is calculated using rms values that include
harm
onic components. Larger harmonic current components cause
the power factor to deteriorate. By contrast, since the displacement
power factor (DPF) calculates the ratio of effective power to appar-
ent power from the fundamental voltage and fundamental current,
no volt
a
ge or current harmonic component is included. This is the
same measurement method used by reactive power meters
installed at commercial-scale utility customers' facilities.
Displacement power factor, or DPF, is typically used by the electric
power system, althou
gh powe
r factor, or PF, is sometimes used to
measure equipment in order to evaluate efficiency.
When a lagging phase caused by a large inductive load such as a
moto
r re
sults in a low displacement power factor, there are correc-
tive measures that can be taken to improve the power factor, for
example by adding a phase advance capacitor to the power system.
Displacement power factor (DPF) measurements can be taken
under such circumstances to verify the improvement made by the
phase advance capacitor.
Power factor
demand value
The power factor calculated using the active power demand value
(consumption) and the reactive power demand value (lag) for the
set interval time (usually 30 minutes).
PFdem=
(Pdem+)
2
+(Qdem_LAG)
2
Pdem+
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