A new set of facility for accelerated aging test of composite insulators has been developed at CEPRI (China Electric Power Research Institute). This paper mainly described the measurement and parameters monitoring system of this facility. This system can monitor total six channels current of insulator in real time, and it can also collect the corresponding information at the same time, such as the applied voltage, the environment parameters. Based on the collected data, the system can analyze and statistic the characteristics of the aged leakage current in time, and it can also save the important test data during the whole test procedure. In addition, this system has the capability of auto alarm, auto reset for the unexpected accidents during the test procedure. This system is a powerful system for the research on the aging performance of composite insulator.

The measuring system we used consisted of two UHF sensors with a frequency band of 400 MHZ～1500MHz and a digital oscilloscope with maximum 2 GS/s digital rate in its two channels. The difference in arrival times of UHF signals at two sensors can be measured to assist with locating defects in GIS. The test results in the laboratory indicate that the fault location precision depends on the digital rate of the oscilloscope. In actual site test, if the sample rate is low, it is could not have enough sample plots to recover the real pulse wavefronts, which is difficult to identify the arrival times at the two sensors by the first peak of UHF waveform. In this paper, a new algorithm has been described, which applies cubic spline interpolation to increase points between two real sample points, and improve the location precision of time flight method. And then the distance difference between two waves can be determined by using cross-correlation function. In addition, the application software has been developed to help locate PD source in GIS.

This paper reports on the infuence of sintering conditions on the flashover/preflashover characteristics of alumina insulators in vacuum under an impulse voltage. Four kinds of alumina insulator were studied, which were prepared using the same formula with different sintering conditions. The surface pre-flashover and flashover phenomena of different samples in vacuum have been observed under impulse voltage. Based on the experimental results, the characteristics of pre-flashover and flashover vary with different kinds of test samples. It was found that the insulators with a higher sintering temperature had a lower flashover voltage, and more active pre-flashover. From a scanning electron microscope (SEM) analysis of alumina insulators, we conclude that the methods of preparing alumina samples can affect their microstructure resulting in a change in the pre-flashover and flashover performance as alumina insulators.

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.

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.