Monitoring of the dielectric dissipation factor during oil reconditioning process for transformer drying

In this work, the dielectric dissipation factor test is proposed for determining the duration of reconditioning process for transformer drying out. For this purpose, a case study of a three-phase rectifier power transformer with high moisture content in the solid insulation, in which the drying out process was carried out, is presented. The original oil was replaced with new oil, and this new oil is used as the medium for drying out the cellulose through a recirculation process. Thus, in this procedure, the oil reconditioning process is required. The resistivity, breakdown voltage, and water content are also monitored during the reconditioning of the oil. The results show that this strategy improves the efficiency of the reconditioning of the solid insulation process, mainly by reducing processing times where the modifications in the oil properties do not change significantly. The results are validated with dielectric frequency response analysis.