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.

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 presented some new experimental results observed in our investigation. Based on the experiments, it was found that the different voltage application sequence on the test samples could influence the flashover voltage of the tested samples. Three kinds of voltage application sequences were compared and three kinds of Alumina samples were involved in this paper. In general, the flashover voltage is the lowest if the applied voltage started from a lower voltage (-2kV) at a -2kV step; the flashover voltage could be the highest if the applied voltage started from -22kV. The surface charge distributions were observed after the voltage was applied. According to the experimental results, the change of the flashover voltage of the test samples could be attributed to the state of surface charge distribution with different voltage application sequence.

The interference voltage in the secondary cables through high voltage bus, current transformer and capacitance coupling voltage transformer caused by lightning striking the region of transmission line neighboring substation were analyzed EMTP software package is used to calculate this problem. The equivalent models of different equipments, especially the transient models of current transformer (CT) and capacitance coupling voltage transformer (CCVT), were discussed The analysis results stated that the interference voltage in file secondary cables caused by lightning striking the region of transmission line neighboring substation is serious, which must be paid attention to by electrical engineers.