Analysis and Experiments of Insulation Loss of Transformer Kraft Paper Based on Hotspot Variations

Abstract

The transformer is one of the important components in the electric power system which is used to transmit power from high voltage to low voltage or vice versa. When the transformer is working, there is an increase in temperature in the transformer which has an impact on the degradation of transformer paper and oil. If proper maintenance is not carried out, aging factors such as oxygen, heat, and humidity will produce acids and other substances that can affect transformer insulation. Insulating oil and transformer paper will experience electrical, mechanical and thermal stress which causes a decrease in performance. The remaining service life of the transformer is an important aspect that must be known. The most commonly used method for estimating the life of a transformer is by accelerated aging experiments. Experiments were carried out by soaking kraft paper insulation in diala B shell mineral oil for 30 days with temperature variations of 120℃ and 160℃ . After the experiment, the transformer paper insulation was tested using the tensile strength testing method. Here the indicator of the end of the paper insulation life is the reduced tensile strength to 50% of the initial conditions. The test results show that temperature variations have an impact on the characteristics of paper insulation. Higher temperatures and longer heating durations result in a darker color of paper insulation. This causes depolymerization or a decrease in the mechanical strength of paper insulation with smaller tensile strength value. A decrease in the insulation strength of a transformer can cause damage to the transformer as well as reducing the lifetime of the transformer.