Eaton Power Xpert PXM 4000, User And Installation Manual

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IM02601004E
Page 111
7 Functions on the Graphical Display
7.4. Quality
The Quality section of the Power Xpert Meter outlines the measurements that have been calculated
and describes the health of the system. It includes:
•
TDD Current
•
THD Voltage
•
K Factor
•
Crest Factor
•
Flicker,
•
9’s of Availability(Compliance)
•
PQ Index
%THD
The Total Harmonic Distortions (THD) is the ratio, expressed as a percent, of the rms value of the
ac signal after the fundamental component is removed and inter-harmonic components are ignored,
to the rms value of the fundamental. The formula for THD is provided below. The variables X
1
and
x
n
may represent voltage or current and may be expressed as rms or peak values, as long as all are
expressed in the same fashion.
X
1
= fundamental value of current or voltage.
x
n
= nth harmonic value of current or voltage.
THD CURRENT AND %TDD CURRENT
The THD Current is calculated for phase A, B and C as Ampere; meanwhile, the %TDD is calcu-
lated as a precentage of the peak demand current. The THD Current is individually measured for
Odd, Even and Inter Harmonics. Maximum THD Current is determined using individual phase THD
Currents. All of the THD Current measurements in the meter are trended. Minimum and maximum
values are logged with date and time stamps.