In this paper, the influence of streaming electrification on the creeping discharge of oil-paper insulation system has been investigated, using experimental models. The experimental results indicate that the initial creeping discharge voltage of 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 creeping discharge under oil flowing conditions. Reasons of failure due to dendritic discharge on the surface of barrier boards in power transformers have been revealed in these experiments.

In this paper, the Influences of electrical field on boiling-condensation heft transfer system have been investigated using a cylinder beat transfer model Freon-ll is selected as working fluid. The condensation heat transfer coefficient, the boiling heat flux the saturation pressure are meassured in this investigation. According to the experimental results, it is found that the electrical field can influence best 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 6kv. The experimental results have been discussed, and it is considered that the high electrical field strength change the thermal properties of working fluid.

In this paper, creeping discharge of oil-polypropylene insulating system have been studied using an experimental model with the 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 poly propylene film can influence the ac creeping discharge inception voltage of oil-polypropylene system. The ac inception voltage of this system is increased along with the increase of oil temperature and oil flow rate. Moreover, the ac inception voltage is higher at the position near to oil entrance than that at the position far to oil entrance. Considering the experimental results, a new composite insulating system is put forward for reducing the negative effects of streaming electrification in larger power devices with forced-oil cooling systems.

A measuring system for on-line detecting partial discharge of generators has been designed with the ultra high frequency (UHF) and high frequency (HF) method. It not only has the capability of calibrating the PD level, but also has the excellent ability of anti-interfering on site. The test data shows this technique is very promising.

This paper provides some experimental investigation on the influence of the surface roughness on the flashover performance of ceramics in vacuum. The test samples were prepared with four kinds of ceramics (99.9% Alumina) which were polished by four different SIC abrasives. The flashover performances of 20 kinds of test samples have been tested with an impulse voltage in vacuum. According to the experimental results, it was found that the roughness of the test sample was quite different among different ceramics although the same grinding procedure was used with the same abrasive. It was also found that the flashover performance was influenced by the surface roughness, and there is a trend that the samples with a lower surface roughness have a higher breakdown voltage.