The Significance of Measuring Dielectric Loss Tangent (tg)

  The dielectric loss tangent, also known as the dielectric loss factor or simply dielectric loss, is a highly sensitive test item. It can detect overall moisture, deterioration, and local defects in electrical equipment insulation, whether through or not through, especially in small-volume tested devices. For example, the normal tg value of a transformer bushing is 0.5%, but after moisture, it becomes 3.5%, a seven-fold difference; however, when measured with insulation resistance, the values before and after moisture are not significantly different.

      Due to the high sensitivity of measuring the dielectric loss factor in reflecting the above defects, it has been widely applied in electrical manufacturing and in handover and preventive tests of power equipment. The regulations for dielectric loss testing of electrical equipment such as transformers, generators, and circuit breakers have been specified in the relevant standards.