Influence of temperature variation of oil contamination on electrical performance of power transformer

This paper describes an experimental study of the influence of temperature variation associated with a transformer oil impurity on the electrical performance of HVDC power transformer under a DC field stress. Spherical-spherical electrodes configuration system has been setup to investigate the bridging formation across a 10mm gap distance at 15kV. Cellulosic fiber dust were dispersed into transformer mineral oil with 0.004% weight concentration level. The temperature electromagnetic agitator was used to heat up the contaminated samples to predetermined temperature. Images obtained from a digital optical microscopy during experiments show that the bridge formation behavior changes with temperature variation. It is preceded with initiated on the electrode surfaces and leads to dense bridges across the gap. Electrical current measurements indicate that the current in contaminated oil increases with the temperature. It is also found that the activation energy to initiate the kinetic process for contaminated oil is 0.21ev.