Dissipation/Power Factor Measurement (Tan Delta) on Power Cables

Capacitance, power factor and dissipation factor (tan delta) are important measurements to make in cables and cable accessories in order to assess the overall insulation losses of the insulation. The tests are useful in detecting deteriorated insulation and moisture or other contaminants.

A deviation from acceptable levels gives an indication of a change in the insulating material. Aging processes in the form of a structural modification of the insulation or the ingress of moisture, can increase the dissipation factor. A decrease  factor can be explained, for example, by impregnating loss.

These measurements are useful in determining overall machine integrity when used in conjunction with other inspection activities. Timely periodic checks can identify problems and prevent the breakdown of cable insulation and eventual cable failure.