Ding Li-Jian

Creeping discharge performance of oil-paper insulation with streaming electrification

In this paper, the influence of streaming electrification on the creeping discharge of an oil-paper insulation system has been investigated, using experimental models. Experimental results indicate that the initial creeping discharge voltage of the oil-paper insulation system decreases with oil flow rate. The creeping discharge path develops toward the oil entrance, and there are polarity and position effects on the creeping discharge under oil flowing conditions. Reasons for failure due to dendritic discharge on the surface of barrier boards in power transformers have been revealed in these experiments.

An experimental study of EHD coupled heat transfer

EHD coupled heat transfer systems have been investigated using a double electrode cylinder heat transfer model. Freon-11 is selected as the working fluid. The condensation coefficient, the boiling heat flux and the saturation pressure are measured in this investigation. According to the experimental results, it is found that the electrical field can enhance both boiling and condensation heat transfer. The enhancement of condensation heat transfer is more obvious than that found in a one electrode heat transfer model.

Influence of streaming electrification on creeping discharge of oil-paper insulation system

In this paper, the influences of streaming electrification on creeping discharge of oil-paper insulation systems have been investigated, using an experimental model. The experimental results indicates that the initial creeping discharge voltage of an oil-paper insulation system decreases along with the increase of oil flow rate, the creeping discharge path develops towards the oil entrance, and there are polarity and position effects on creeping discharge under flowing oil conditions.<<ETX>>

Electrostatic enhanced heat transfer in a dielectric liquid

In this paper, the phenomena of electrostatic enhanced heat transfer in a dielectric fluid have been investigated experimentally using a horizontal model pipe. The saturation pressure in the model pipe, the heat flux both in heated and cooled ends are all measured under high DC voltage. Experimental results show that the heat transfer properties of dielectric working liquids can be improved by the electrostatic field.

Influences of electrical field on boiling-condensation heat transfer system

In this paper, the influences of electrical field on boiling-condensation heat transfer systems have been investigated using a cylinder heat transfer model. Freon-11 is selected as working fluid. The condensation heat transfer coefficient, the boiling heat flux and the saturation pressure are measured in this investigation. According to the experimental results, it is found that the electric field can influence heat transfer system. The boiling heat transfer is enhanced by the applied voltage, and the saturate vapor of working fluid is condensed on the high voltage electrode directly when the applied voltage is higher than 6 kV. The experimental results have been discussed, and it is considered that the high electrical field strength changes the thermal properties of the working fluid.

A preliminary study of oil-polypropylene insulating system

In this paper, the creeping discharge of oil-polypropylene insulating systems has been studied using an experimental model with flowing oil under AC voltage. The AC creeping discharge inception voltage of the oil-polypropylene system has been tested under varied conditions. According to the experimental results, all of the oil temperature, the oil flow rate and the position of polypropylene film can influence the AC creeping discharge inception voltage of the oil-polypropylene system. The AC inception voltage of this system increases along with the increase of oil temperature and oil flow rate. Moreover, the AC inception voltage is higher at a position near to the oil entrance than that at a position far from the oil entrance. Considering the experimental results, a new composite insulating system is put forward for reducing the negative effects of streaming electrification in large power transformers with forced-oil cooling systems.

Influence of streaming electrification on creeping discharge of oil-paper insulation systems. (Study on dendritic discharge of barrier boards in power transformers)

In this paper, in order to investigate failures due to the dendritic discharge on the surface of barrier boards in power transformers, streaming electrification and its influence on creeping discharge of oil-paper insulation systems have been studied using experimental models. According to the experimental results, the reasons of the failures have been revealed. It has been found that the creeping discharge of oil-paper insulation systems are related to streaming electrification and, as the streaming electrification makes the creeping discharge voltage lower, the creeping discharge path is also influenced.<<ETX>>