Schneider Electric 4000 Power Analysis Values, On page 68 summarizes the power analysis values

Chapter 4—Metering Capabilities							63230-300-212
Power Analysis Values								April 2001
POWER ANALYSIS VALUES	The circuit monitor provides a number of power analysis values that can be
	used to detect power quality problems, diagnose wiring problems, and more.
	Table 4–5 on page 68 summarizes the power analysis values.
	• THD. Total Harmonic Distortion (THD) is a quick measure of the total
	distortion present in a waveform and is the ratio of harmonic content to the
	fundamental. It provides a general indication of the “quality” of a
	waveform. THD is calculated for both voltage and current. The circuit
	monitor uses the following equation to calculate THD where H is the
	harmonic distortion:
	2		+	2	+	2	+
	THD =	H2		H3		H4		x 100%
				H 1

•thd. An alternate method for calculating Total Harmonic Distortion, used widely in Europe. It considers the total harmonic current and the total rms content rather than fundamental content in the calculation. The circuit monitor calculates thd for both voltage and current. The circuit monitor uses the following equation to calculate thd where H is the harmonic distortion:

	H 2	+ H 2 +	H 2 +
thd =	2	3	4	x 100%

Total rms

•TDD. Total Demand Distortion (TDD) is used to evaluate the harmonic voltages and currents between an end user and a power source. The harmonic values are based on a point of common coupling (PCC), which is a common point that each user receives power from the power source.

The following equation is used to calculate TDD where Ih is the magnitude of individual harmonic components, h is the harmonic order, and IL is the maximum demand load current in register 3233:

255
	Σ	Ih2
TDD =	h=2		x 100%

IL

•K-factor. K-factor is a simple numerical rating used to specify transformers for nonlinear loads. The rating describes a transformer’s ability to serve nonlinear loads without exceeding rated temperature rise limits. The higher the K-factor rating, the better the transformer’s ability to handle the harmonics. The circuit monitor uses the following equation to

calculate K-factor where Ih is harmonic current and h is the harmonic order:

SUM (Ih2 h 2)

K =

2

SUM I rms

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