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4.4 Power Analysis Values
4.4.1 Total Harmonic Distortion Measurement
The total harmonic distortion (THD) is a measurement of the harmonic distortion and is defined as the ratio
between the power of the harmonic frequencies above the base frequency and the power of the base frequency.
The total harmonic distortions for current and voltage are calculated using the following formulas.
Total Harmonic
Distortion for Current
Total Harmonic
Distortion for Voltage
4.4.2
Demand Calculation Method
The power meter provides measured values for current demand, active power demand, reactive power
demand and apparent power demand. You can also calculate the last, present, predicted and peak demand
values from above measured values. The power meter supports fixed block interval demand methods. The
example shown below uses a 15-minute interval. You can select an interval from 1 to 60 minutes. The meter
updates the present, predicted and peak demand values every second, and updates the last demand value at
the end of the interval. The power meter treats last demand value as the present demand after updating.
Last demand: The power meter calculates the value when the last interval ends.
Present demand: The power meter calculates the value during the current interval.
Predicted demand: The power meter calculates the value before the current interval ends.
Peak demand: The power meter calculates the maximum value during the current interval.
Demand value is the average value that is calculated
when the last interval ends.
15-minute interval 15-minute interval
15
30
15-minute interval
45
60
C h a p t e r 4 O p e r a t i o n
Tim e (minutes)
4 - 9
4_
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