Dielectric Dissipation Factor ( Tan Delta) and Oil Resistivity ( Specific Resistance)
Tan Delta also called Loss Angle or Dielectric Dissipation Factor (DDF) or Power Factor (PF) testing, is an electrical dielectric test on the insulating oil used to determine its quality.
In one sentence it can be said that tanδ is a measure of the imperfection of dielectric nature of insulation materials like oil. Thus testing and measurement of it on periodic basis is very important
These Parameters are very sensitive to the Presence of Soluble Polar contaminants, ageing products or colloids in the oil. Changes in the level of the contaminants can be monitored by measurement of these parameters even when contamination is so slight as to be near the limit of chemical detection.
Higher value of DDF, or low Values of resistivity, may deleteriously affect the dielectric losses and/or the insulation resistance of the electrical equipment.