Dielectrical dissipation factor measurements on stator windings – Part 1: Survey answers

Dielectric Dissipation Factor (DDF) measurement, also known as tangent delta (tanδ) or power factor testing, is the measurement of the dielectric losses in an Electrical Insulation System (EIS). In the field of rotating electrical machines, the method is used for assessing the condition of an EIS and the consistency in the manufacturing quality of individual stator bars/coils. Dielectric dissipation factor measurements are widely used, all over the world, to assess the condition of, in general, high voltage stator winding insulation of rotating machines. The DDF measurement is used to evaluate the quality of complete stator windings, both as an acceptance test after manufacturing and as test to evaluate the condition of in-service stator windings due to ageing and/or contamination.