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 has investigated the thermally stimulated current (TSC) of Alumina ceramics using a uniform electrode system. Experimental results with different Alumina ceramics showed that TSC characteristics of the samples prepared with varied metal oxide additives was different. The trap distribution parameters were calculated from TSC curves, the calculation results show that the additives significantly influence the trap distribution.

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.