Rudi Kurnianto

Statistical study on tree inception voltage of silicone rubber and epoxy resin

Weibull distribution has been used widely by many researches around the world especially in the analysis of high voltage experimental data. Unfortunately, most of the experimental data analysis was not following the accurate statistical technique. Thus in this paper, a statistical study on the tree inception voltage of silicone rubber and epoxy resin is presented. The tree inception voltage of silicone rubber and epoxy resin was measured via camera-equipped online monitoring system. The leaf-like specimen was used as test sample. The experiment was performed based on IEC 1072:1991 “Methods of Test for Evaluating the Resistance of Insulating Materials against the Initiation of Electrical Trees”. The obtained results were analysed statistically by using fitting method. Anderson-Darling goodness-of-fit test was performed in order to obtain the best fitting distribution. Comparison exercise was made between the fitted distribution and Weibull distribution. Based on Anderson-Darling tests, the tree inception voltage of silicone rubber and epoxy resin was best fitted with Johnson SB distribution. Based on this fitted distribution, the value of tree inception voltage for silicone rubber and epoxy resin was calculated and equalled to 3.1529 kV and 4.6528 kV respectively. Thus, it was found that, the fitting method by means of Anderson-Darling goodness-of-fit test was successful to recognize the best fitted distribution for the value of tree inception voltage for silicone rubber and epoxy resin.

Time lag in CM-II electrode system attributed to dielectric surface conditioning

This paper deals with a digest on discharge time lag characteristics in a cylindrical void bounded polymethyl-methacrylate (PMMA) and metal using the CIGRE method II (CM-II) electrode system. The specimens were treated by plasma irradiations (0, 3, 6, 11, 16, 21 seconds) simulating material ageing in service which are very difficult to measure. It was found that, under room temperature, the longer plasma irradiation to the void surface will result in higher degree of surface roughness indicated by the increase of surface protrusion sizes. The statistical discharge time lag (SDTL) has been studied using square pulse voltage with rising time 40 μs, through 64 pulses. The SDTL value is inversely proportional to the surface conditioning. For a particular time period of plasma irradiation (3 s), the specimens seem to recover its insulating property after given recovery time of 20, 60, and 180 minutes compared to that of without recovery time.