The Experimental Study of Breakdown Characteristics for Oil-paper Insulation under Low Temperature

The large power transformer will operate under low temperature in Inner Mongolia, Xinjiang and Northeast provinces in China. In order to study the breakdown characteristics of transformer oil-paper insulation at low temperature, a high-voltage and low-temperature test system for transformer oil-paper insulation breakdown characteristics was established. The effects of content Water to oil and oil-paper composite insulation breakdown characteristics in -50 degrees C to 20 degrees C range were obtained. The experimental results show that the breakdown voltage of the transformer oil decreases and then increases with the decrease of the temperature. For the oil-paper composite insulation, when the water content is low, the breakdown voltage increases with the decrease of the temperature. When the water content is high, the breakdown voltages decrease significantly in the early stage. When the temperature is below -10 degrees C, the breakdown voltage increase sharply but decrease significantly after reach the peak value. The lower temperature correspond to the minimum breakdown voltage, and the lower the breakdown voltage.