Have a look at chapter 6.2.3.1 Simplifications for small Dissipation / Power Factor on page 31.
6.2 Background
Insulation power factor (PF) is one of the most common tests performed on transformers,
regulators, reactors, bushings, and other supported equipment and should be conducted as part of
factory, acceptance, diagnostic and routine assessment. Though dielectrics have inherent losses
due to construction materials, PF measurement is most effective at detecting the relative levels of
moisture and contamination. Evaluation of the capacitance measurement is effective in detecting
physical defects that lead to changes in the dielectric’s geometry.
6.2.1 Imperfect dielectric
The properties of true dielectric insulations are often simplified and expressed as imperfect
dielectrics. An imperfect dielectric is a dielectric where the energy necessary to create an electric
field is not returned to the electric field when the energy is removed. The energy is converted into
heat in the dielectric. Conversely, a perfect dielectric has zero conductivity, and there are no
absorption effects. A high vacuum is an example of a perfect dielectric. Most dielectrics tested are
considered imperfect dielectrics due to the presence of moisture, contaminants, and other inherent
polar molecules.
Info:
Info:
The CAPO is able to display either dissipation factor tan δ or power factor
cos φ based on the users choice.
In cases where the angle is very small, dissipation factor tan δ practically
equals power factor cos φ.
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