Experimental investigation of insulation parameters affecting power transformer condition assessment using frequency domain spectroscopy

In recent years, dielectric relaxation methods in time and frequency domains have been evolved as a tool for the assessment of transformer insulation. However, it has been observed that the results of these tests are highly influenced by several factors viz. the temperature of the insulation, the magnitude of the test voltage, the geometry of transformer insulation structure. In the present work, a detailed analysis of the influence of the above-mentioned factors on the dielectric response data is presented by performing measurements on a prorated transformer model. A novel experimental procedure is suggested to acquire a database to study the effect of insulation duct geometry on the relaxation measurements. Possible corrective actions are suggested to improve transformer insulation diagnosis.