Experimental Research on Breakdown Characteristics of Transformer Oil at Low Temperature

Abstract

With the development of power systems, the capacity of power transformers has continuously increased, and the requirements for their safety have also been increasing. Because of the low winter temperatures in northern China, the transformer boot process will inevitably face the test of low-temperature environment. Therefore, it is of great significance to study the effect of low temperature on the insulation performance of transformers to ensure the safe operation of power transformers. In this paper, the change of the micro-water content in the transformer oil was studied by means of experiments, and the influence of temperature on the insulating oil breakdown characteristic was analyzed. The results show that the two processes of micro-water dissolution and precipitation in transformer oil are not completely reversible under low temperature environment; the breakdown voltage of transformer oil shows a trend of decreasing first and then rising during the cooling process. A detailed analysis of this trend is carried out theoretically, and it is concluded that when the low temperature condition is unavoidable, the moisture content in the transformer oil should be minimized.