EET PMC-33M-A User Manual

CET Electric Technology
32
replace it with manual operation. A manual reset will
cause the Max. Demand of This Month to be transferred
to the Max. Demand of Last Month and then reset. The
terms This Month and Last Month will become Since Last
Reset and Before Last Reset.
Predicted
Response
The Predicated Response shows the speed of the predicted
demand output. A value between 70 and 99 is
recommended for a reasonably fast response. Specify a
higher value for higher sensitivity.
70* to 99
Table 4-4 Demand Setup
4.3 Power Quality
4.3.1 Phase Angles
Phase analysis is used to identify the angle relationship between 3-phase Voltages and Currents.
For WYE connected systems, the per phase difference of the Current and Voltage angles should
correspond to the per phase PF. For example, if the PF is 0.5 Lag and the Voltage phase angles are 0.0°,
240.0° and 120.0°, the Current phase angles should have the values of -60.0°, 180.0° and 60.0°.
4.3.2 Power Quality Parameters
The PMC-33M-A provides the following PQ parameters:
4.3.2.1 Harmonics
The PMC-33M-A provides harmonic analysis for THD, TOHD, TEHD and individual harmonics up to the
31
st
order. All harmonic parameters are available on the front panel and through communications. In
addition, the PMC-33M-A also provides TDD, K-factor and Crest-factor measurements for current.
4.3.2.2 TDD
Total Demand Distortion (TDD) is defined as the ratio of the root mean square (rms) of the harmonic
current to the root mean square value of the rated or maximum demand fundamental current.
TDD of the current I is calculated by the formula below:
where
I
L
= maximum demand of fundamental current
h = harmonic order (1, 2, 3, 4, etc.)
I
h
= rms load current at the harmonic order h
4.3.2.3 K-Factor
K-Factor is defined as the weighted sum of the harmonic load current according to their effects on
transformer heating, as derived from ANSI/IEEE C57.110. A K-Factor of 1.0 indicates a linear load (no
harmonics). The higher the K-Factor, the greater the harmonic heating effect.
)(
)(
K
2
hh
1h
2
hh
1h
max
max
h
h
I
hI
Factor







where
I
h
= h
th
Harmonic Current in RMS
h
max
= Highest harmonic order

EET PMC-33M-A Specifications

General

Brand	EET
Model	PMC-33M-A
Category	Measuring Instruments
Language	English