Measurement Computing WavePort 312P rev.1.0 - Manual (Page 81)

Glossary
PowerVista User’s Manual Glossary 11-5
Total Harmonic Distortion (THD)
The total "root sum square" harmonic distortion in percent of fundamental.
SQRT[V
2
2
+ V
3
2
+ V
4
2
+ ...]
V
THD
=
________________________________ •••• 100%
V
fund
Total Power Factor
The ratio of the total RMS power input, in watts, to the total RMS volt-ampere input. This definition includes
the effect of harmonic components of current and voltage (distortion power factor), and the effect of phase
displacement between current and voltage. Volt-amperes are the product of RMS voltage and RMS current.
Transient
A disturbance that is temporary or "transient" involving voltage or current or both. This term covers a large
number of power system disturbance types including: impulses, damped oscillatory transients, lightning
transients, switching transients, and many more fast power system disturbances.
Transformer Derating Factor
This derating factor is applied to transformers according to ANSI Standard C57.110-1986 when supplying
harmonic currents. The derating factor is the maximum fundamental current in per unit (1.0 pu being
transformer full load capability) that a unit can safely withstand with the additional harmonic currents. Pecr is
defined as the eddy current loss factor.
D-Factor = Pecr/( 1 + Pecr (K-factor) )
V-SUM
The linear sum of RMS voltages to generate an estimate of peak voltage. This is normally used in the design of
harmonic filters and, in particular, the specification of properly voltage rated capacitor units. Capacitor
dielectrics have limits in the peak voltage stress they can withstand.
H
V-Sum = ∑ ∑ ∑ ∑ V
h
h=1