The measurement is part of the large set of tests whose purpose is to determine the state and characteristics of the insulators: insulation, IP, DAR, and DD, just to name a few. The characteristic of the measurement, unlike the others mentioned, is that of being carried out in alternating mode and, therefore, being a function of different factors: test voltage, frequency and intrinsic capacity of the sample. If while an insulation measurement will always give the same result, i.e., the measurable resistance value between casing and winding, the Tan Delta test, being a function of the capacitive component (typical of the piece under test), can provide different results depending on the nature of the piece.

The indication provided by the Tan Delta test is useful for determining the quality of the insulators mounted in motors, stators, transformers and, in general, electrical machines. Other fields of application are the quality control of cables, and their state of wear or contamination (typically water), which can lead to the degradation of the insulating properties of the materials used and the formation of so-called water trees, and infiltrations of humidity that run through the cable internally, leading to insulation loss and other negative factors.

Unlike some insulation tests, the verification is applied to products being manufactured, since the measured data can be considered typical for that particular product in that particular phase of the production process.