K-factor is a weighting of the harmonic load currents 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 effects.
When a non-linear load is supplied from a transformer, it is sometimes necessary to derate the transformer
capacity to avoid overheating and subsequent insulation failure.
The reason for this is that the increased eddy currents caused by the harmonics increase transformer losses
and thus generate additional heat. Also, the RMS load current could be much higher than the kVA rating of
the load would indicate. Hence, a transformer rated for the expected load will have insufficient capacity.
The K-Factor is used by transformer manufacturers and their customers to adjust the load rating as a function
of the harmonic currents caused by the load(s).
Generally, only substation transformer manufacturers specify K-factor load de-rating for their products. So,
for K-factors higher than 1, the maximum transformer load is de-rated.
K-Factor Calculation
The K-factor is a number derived from a numerical calculation based on the summation of harmonic
currents generated by the non-linear load. The higher the K-factor, the more significant the harmonic
current content.