The effect of surface-treated inorganic filler on the voltage-endurance of Low-Density Polyethylene has been investigated.The inorganic filler used for the test is clay which was treated by adding silane and high speed stirring at 60 -70°C' Both LDPE with treated filler (filled LDPE) and LDPE without filler (unfilled LDPE) were used for voltage endurance, electrical breakdown and dielectric loss experiment. The experimental results show that the life index of filled-LDPE is higher than that of unfilled LDPE. As the aging time prolongs, the residual electrical breakdown strength of filled-LDPE increases and the dielectric loss factor (tan6) of filled-LDPE decreases at 7Ooc, respectively. On the base of experimental results, a deep electronic trap mechanism for the effect of inorganic filler treated with coupling agent is put forward. It is considered that the surfacetreated filler with silane may supply deep electronic traps reducing the carrier mobility and carrier density in filled-LDPE to suppress electrical tree propagation. Thermal stimulated current (TSC) and electrical treeing experiments have been performed. The experimental results are consistent with theoretical analyses.

If a fault occurs in an underground power cable it is necessary to find the fault point as quickly and accurately as possible. Although Murray loop method and pulse radar method have been extensively used for cable fault locating, the fault line needs to be removed from service and connected to detection equipment, which will take much time and effort. In the present paper, a new fault location method, which integrates fiber optic distributed temperature (FODT) sensor into cable, is introduced.The FODT sensor, which is applied to fault detection of XLPE insulated underground cable in resistance grounded power system, can find fault point immediately. The maximum detection distance, distance resolution and processing time for fault location are IOkm, lm and 30s respectively.

On-line monitoring of Partial Discharge (PD) is useful in indicating the condition of electrical insulation of large generators. To ensure correct PD monitoring, electrical noise must be rejected. In this paper, after a brief review of progresses in on-line PD monitoring technique for electrical machines, novel noise rejection techniques were presented. PD monitoring results from generators in Qinling Power Plant were also given.

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Many papers are involved with the mechanical and electrical properties of rubber or composite cured in traditional way but few involved with the properties of composite dynamicly vulcanized. The effect of dynamic vulcanization on mechanical and electrical properties of PPEPDM composite was studied in our laboratory. The relationship between the mechanical properties of composite and the vulcanizator concentration and ratio of PPEPDM is presented in this paper. As the ratio of PPEPDM increas, the tensile strength of composite increas and elongation decrease. When vulcanizator content is about 1.2 by weight percent both mechanical and electrical properties reach optimual values. In order to understand the dependence of mechanical properties of composite on vulcanization concentration and PPEPDM ratio, scanning electronic microscopy (SEM) is used for the examination of micro-morphology of the composite. From the SEM photograph it can be seen that the mechanical propertise of composite depend on uniform distribution of the rubber particle in PP matrix. Obviously, dynamic vulcanization contributed to formation of small particles and improvement of compatibility between PP and EPDM. Therefor the PPEPDM composite posseses good mechanical properties. The electrical propertis, insulation resistivity and dielectric loss factor (tan6), of the composite with improved mechanical properties were also measured and the results of the experiment satisfied. Therefore dynamic vulcanization is an approach for improving the mechanical and electrical peoperties of PP/EPDM composite.